RU2407169C1 - Device and method for optical line terminal (olt) and optical network unit (onu) in wavelength-independent wavelength division multiplex passive optical networks - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention can be used in wavelength division multiplex passive optical networks (WDM-PON), using a conventional technique of multiple use of a downlink optical signal. The WDM-PON system includes: a source light (SL) unit which forms initial light whose wavelength intervals and medium wavelength of which is controlled using at least one initial light source; an optical line terminal (OLT) which receives the source light with wavelength division multiplexing of the source light unit which transmits a downlink optical signal to a WDM-PON user and receives an uplink optical signal from the user; and an optical network unit (ONU) which receives a downlink optical signal from OLT, which levels and modulates the downlink optical signal using an uplink data stream.

EFFECT: control of equipment such that, different types of optical transmitting device must be provided for functioning, control and replacing the system.

43 cl, 51 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a method for equalizing a modulated optical signal in a reflective semiconductor optical amplifier (RSOA) or semiconductor optical amplifier (SOA) to reuse the resulting optical signal as an upstream optical signal, and more particularly, to a control device for improving the uniformity of the input optical signal and reusing the optical signal by introducing a signal whose polarity is opposite hydrochloric polarity optical signal RSOA, and a SOA structure therefor.

The present invention relates to a downlink optical transmission apparatus and method using a wavelength independent light source in a passive optical network with wavelength division multiplexing (WDM-PON), and an optical line terminal (OLT) using a downlink optical transmission apparatus, and more specifically, to a downlink optical transmission apparatus and method using a wavelength independent light source in a WDM-PON that can efficiently perform control, operation and maintenance using / repairing an OLT in a WDM-PON at low cost by using a multi-wavelength light source (MWLS) or a broadband light source (BLS) as a wavelength independent light source and using an optical transmitter corresponding to a wavelength independent light source in an OLT, and OLT using the downlink optical transmission apparatus and method. The present invention relates to a network configuration method and an uplink / downlink optical communication device that are used to configure a passive multiplexed spectral density multiplexing (spectral division multiplexing) optical network (DWDM-PON), and more particularly, to a network structure to achieve Hybrid WDM-TDMA-PON by combining DWDM-PON or WDM-PON with time division multiple access (TDMA) as well as OLT and optical network module (ONU) used in network structure.

This work was supported by the IT R&D MIC / IITA program [2007-S-014-01, Metro-Access Integrated Optical Network Technology].

State of the art

To configure a passive optical network with wavelength division multiplexing (WDM-PON) using a traditional reflective semiconductor optical amplifier (RSOA), a method is proposed in which an optical signal that is modulated into a downstream data stream through a central station (CO) is transmitted to The optical network terminal RSOA (ONT) and the RSOA are controlled in the gain saturation region with respect to the power of the input optical signal so as to significantly reduce the difference between the “0” level and the “1” input level one optical signal when the input optical signal is re-modulated into the upstream data stream.

In this optical signal reuse method, when RSOA gain saturation occurs at lower optical power, the optical power budget in the optical communication line increases, and therefore, the gain saturation power must be reduced to be as low as possible, and the optical signal included in the RSOA should be reinforced sufficiently for uplink transmission. Therefore, the RSOA gain should be large enough.

However, in reality, the RSOA compression ability in the gain saturation region is limited, and therefore, there is a limitation on reducing the extinction coefficient (ER) of the input optical signal to a sufficient degree. In this case, when the residual extinction coefficient is directly directly modulated again by the upstream data stream, the residual extinction coefficient is reflected in the thickness of level 1. Since level 1 is thicker, the quality of the upstream transmission is degraded. If level 1 is thicker than a specific thickness, the quality of the upstream transmission deteriorates rapidly.

Accordingly, the extinction coefficient of the downstream optical signal may need to be reduced to a minimum that is exactly sufficient for transmission. At this time, due to the low extinction coefficient of the downstream optical signal, a power penalty may occur in the downstream transmission. In particular, when the light wavelengths of the devices configuring the downlink are even slightly misplaced, a sensitivity appears, due to which the extinction coefficient of the optical signal entering the receiving device becomes smaller than the extinction of the optical signal output from the transmitting device, and the transmission quality is rapidly deteriorating .

Recently, thanks to the intensification of hybrid audio / data / broadcast services, research and development has been actively carried out around the world based on wavelength division multiplexing (WDM) networks.

Data exchange between the central base station and the terminal in the WDM-PON is performed using the wavelengths that are assigned at each terminal. In WDM-PON, since a closed wavelength is used for each terminal, excellent security is guaranteed, more communication services are possible and various transmission techniques can be applied (for example, different data rates, different frame formats, etc.) to the respective terminals or services.

The multiple use method of the downward light wavelength, of the many WDM-PON configuration methods that have been proposed to date, generates an upward optical signal by repeatedly using the downward light wavelength. Thus, the ascending light wavelength is equal to the descending light wavelength, the free spectral range (FSR) of the WDM-based multiplexing / demultiplexing module should not be taken into account, a multi-stage remote node can also be configured, and many types of subscriber networks can be configured.

The following is described in detail WDM-PON, using the method of reusing downlink optical signal.

13 illustrates a WDM-PON configuration according to a conventional downlink optical signal reuse method. Referring to FIG. 13, a WDM-PON includes an optical line terminal (OLT) 1300, an optical line 1310, a wavelength division multiplexing / demultiplexing unit 1320, and an optical network unit (ONU) 1330.

First, the corresponding elements of the OLT 1300 are described below, with the OLT 130 located at the telephone exchange.

The OLT 1300, as illustrated in FIG. 13, includes a protocol processor 1301, a plurality of fixed wavelength optical transmitters 1302 from Tx # 1 to Tx # N, a wavelength multiplexer 1303, an optical circulator 1304, a wavelength demultiplexer 1305 and a plurality of optical receivers 1306.

If the downstream electrical signal is transmitted from the protocol processor 1301 to the optical transmitters 1302 with a fixed wavelength from Tx # 1 to Tx # N, each optical transmission device 1302 with a fixed wavelength outputs an optical signal corresponding to the downstream electrical signal to the multiplexer 1303 in length the waves.

Next, the wavelength multiplexer 1303 combines the optical signals received from the optical transmitters 1302 with a fixed wavelength from Tx # 1 to Tx # N with each other, and then transmits the resulting signal through the optical line 1310 to the length multiplexing / demultiplexing unit 1320 waves, which is in a remote site. Optical signals are divided according to their wavelengths by a wavelength multiplexing / demultiplexing unit 1320. The wavelength multiplexing / demultiplexing unit 1320 operates as a wavelength demultiplexer when a downlink signal is received, and operates as a wavelength multiplexer when an uplink signal is received.

Optical signals that are separated according to their wavelengths by the wavelength multiplexing / demultiplexing unit 1320 are transmitted to the corresponding ONU 1330.

The elements of each ONU 1330 are described in detail below. Here, each ONU 1330 includes a tap splitter 1331, an optical transmitting device 1332, an optical receiving device 1333, and a protocol processor 1334. The optical transmitting device 1332 may be a wavelength-independent semiconductor optical amplifier.

A tapper combiner module 1331 transmits some of the downstream optical signals transmitted from the wavelength demultiplexer 1320 to the optical receiver 1333 to recover them as downstream signals, and transmits the remainder of the downstream optical signals to the optical transmitter 1332.

Then, if the optical transmitting device 1332 receives an upward electrical signal from the protocol processor 1334, the optical transmitting device 1332 generates an upstream optical signal by repeatedly using the downstream optical signal received from the tapping combiner 1331, and transmits the upstream optical signal to the ONU 1330.

Since the optical transmitting device 1332 uses a semiconductor optical amplifier, which is a wavelength independent light source, there is no equipment control problem, and the type of optical transmitting device can process all WDM channels.

However, in the above WDM-PON using a conventional downlink optical signal reuse method, since the optical transmitting device that is used in the telephone exchange in the WDM-PON is a fixed wavelength optical transmitting device (e.g., DFB-LD, which outputs the same light wavelength, an external resonant laser with a fixed wavelength, a surface radiation laser with a vertical volume resonator (VCSEL), etc.) using a fixed light source th wavelength, require different types of optical transmitters corresponding to the number of wavelengths that are available in the telephone exchange. The manufacture, installation and management of light sources according to wavelengths gives a large load to all users and suppliers and thus increases the cost of the system. Thus, in the WDM-PON according to the traditional method of reusing the downlink optical signal, a problem of controlling the equipment arises in that various types of optical transmitting devices must be provided for operation, control, replacement, etc. systems.

DETAILED DESCRIPTION OF THE INVENTION

Technical challenge

The present invention provides a control device for equalizing the optical power of an input optical signal to reuse the input optical signal as an upward optical signal, regardless of the gain saturation of the reflective semiconductor optical amplifier (RSOA), by applying a current signal whose polarity is opposite to the polarity of the input optical signal , to RSOA, and thereby dynamically adjusting the size of the optical power gain of RSOA, and RSOA and SOA structures of a semiconductor optical amplifier that are suitable for a control device.

The present invention also provides a downlink optical transmission apparatus and method using a wavelength independent light source in a passive optical network with wavelength division multiplexing (WDM-PON), which enables efficient management, operation and maintenance of an optical line terminal (OLT) ) WDM-PON at low cost using a multi-wavelength light source (MWLS) or a broadband light source (BLS) as a wavelength-independent light source, and thus m using an optical transmitter corresponding independent of the light source wavelength and the OLT, uses the device and method of downlink optical transmission.

The present invention also provides a method for configuring a wavelength independent OLT in a WDM-PON or in a WDM-TDMA-PON by setting MWLS or BLS to output multiple wavelengths therein to introduce undamped oscillation (CW) output from MWLS or BLS , into a light wavelength independent semiconductor optical amplifier (SOA) so that MWLS or BLS can be used as an optical transmission module.

Unlike OLT wavelength independence, wavelength independence of the optical network module (ONU) is achieved by transferring some of the downstream optical signals received from the OLT to a photodiode (PD) so that each downstream optical signal is restored to the electronic signal through an electrical an amplifier (e.g., a transimpedance amplifier (TIA) or a limit amplifier (LA)), and transmitting the remaining region of the downstream optical signals to a semiconductor optical amplifier (SOA). In order to reuse each downstream optical signal input to the semiconductor optical amplifier as an upstream optical signal, it is necessary to erase the downstream data stream included in the downstream optical signal through the process of reusing the light wavelength. To this end, the present invention provides a method for introducing (injecting) direct current coupling (FFCI).

Technical solution

According to an aspect of the present invention, there is provided a control circuit of a reflective semiconductor optical amplifier (RSOA), including: a splitter dividing the input optical signal into a first signal and a second signal; An RSOA having one active region that reflects a second signal from a reflective face and into which a combined signal is introduced from a signal with a polarity opposite to that of the second signal and a modulation signal for modulating a second signal reflected from the reflective face into an output optical signal; a data photodiode converting the first signal into a current signal; a transimpedance amplifier receiving a current signal from the data photodiode and amplifying the current signal into a voltage signal with a polarity opposite to that of the first signal; a radio frequency (RF) amplifier receiving a voltage signal from a transimpedance amplifier and amplifying a voltage signal into an equalization signal suitable to equalize the optical amplitude of the second signal; an RF delay module receiving the equalization signal from the RF amplifier and adjusting the output time of the equalization signal so that the second signal is maximally aligned; and a signal combining module combining an equalization signal with a modulation signal and inputting the result of combining into one active RSOA region.

According to another aspect of the present invention, there is provided a downlink optical transmission apparatus using a wavelength independent light source that is used in an optical line terminal of a passive optical network with wavelength division multiplexing (WDM-PON), including: a source light module generating multiwave optical signal; a wavelength multiplexing / demultiplexing module dividing a multiwave optical signal according to wavelengths; an optical transmitting device generating a downward optical signal using an optical signal received from a wavelength multiplexing / demultiplexing unit in response to a plurality of electrical signals received from an external device; and a circulator transmitting the multi-wavelength optical signal to the wavelength multiplexing / demultiplexing unit or transmitting the optical signal output from the wavelength multiplexing / demultiplexing unit to the subscriber side, wherein the wavelength multiplexing / demultiplexing unit combines a plurality of downstream optical signals generated by optical transmitting device, with each other.

According to another aspect of the present invention, there is provided a wavelength division multiplexing (WDM-PON) passive optical network system including: a source light driver that generates the source light, the wavelength interval and the center wavelength of which are adjustable for at least using a single source of light; an optical line terminal (OLT) receiving the source light from the source light shaper, transmitting the downlink optical signal to the WDM-PON subscriber, and receiving the upstream optical signal transmitted from the subscriber; a network module (ONU) transmitting an uplink optical signal into which a downlink optical signal received from the OLT is modulated so that the downlink optical signal includes an upstream data stream.

Benefits

In a passive optical network with wavelength division multiplexing (WDM-PON), which uses a reflective semiconductor optical amplifier (RSOA) according to a method for reusing a downlink optical signal using the compression effect in amplitude in the gain saturation region, in fact, since there is a limitation on the performance of RSOA compression in a gain-saturated state, it is difficult to compress the downstream signal sufficiently so that the upstream transmission is possible in sufficient extent when the extinction coefficient of the downlink signal is large. To solve this problem, the present invention significantly reduces the extinction coefficient of the input optical signal by dynamically adjusting the current input to the RSOA according to the amplitude of the input optical signal.

Accordingly, it is possible to further reduce the thickness of level 1 of the upstream optical signal and thereby reduce the penalty on the power of the upstream transmission, thereby improving the transmission quality. In addition, since the extinction coefficient of the downstream optical signal can be maintained at a value higher than the value that is generally used, it is possible to reduce the downward power penalty compared to the conventional method in which the extinction coefficient of the downward optical signal is always kept low. In particular, it is possible to prevent sensitivity by which the extinction coefficient of the downstream optical signal becomes smaller than the extinction coefficient required for transmitting the optical signal, and thereby the transmission quality deteriorates rapidly when the light wavelengths of the devices configuring the downlink are even slightly wrong arranged.

Therefore, the quality and reliability of the downstream transmission can be improved by sufficiently increasing the extinction coefficient of the downstream optical signal, and the quality and reliability of the downstream transmission can also be improved by sufficiently equalizing the modulated downlink optical signal in the RSOA.

As described above, according to the present invention, by inserting a multi-wavelength light source (MWLS) or broadband light source (BLS) into an OLT and thereby using a wavelength independent semiconductor optical amplifier instead of a fixed wavelength semiconductor optical amplifier as an optical transmitting device for OLT, OLT equipment management problem can be resolved.

Furthermore, according to the present invention, by creating a spacing between the output light wavelengths of the multi-wavelength light source smaller than the bandwidth of the wavelength multiplexing / demultiplexing unit so that multiple wavelengths exist for each WDM channel, the problem of wavelength stability of the multi-wavelength source can be solved light and improve system stability.

As described above, according to the present invention, in WDM-PON, wavelength independence of the OLT is achieved by introducing the source light from MWLS or BLS into the OLT and by using a wavelength independent optical transmitting device for OLT. Accordingly, since one part of the optical transmission OLT can receive and process different wavelengths, OLT can be implemented using one part of the optical transmission regardless of the number of WDM-based light wavelengths used.

In addition, in order to achieve independence from the ONU wavelength, the present invention provides a method for dynamically adjusting the current to be introduced into the RSOA according to the amplitude of the input optical signal. Therefore, it is possible to further reduce the thickness of level 1 of the upstream optical signal and thereby reduce the penalty on the power of the upstream transmission, thereby improving the transmission quality.

In addition, since the extinction coefficient of the downstream optical signal can be maintained at a value higher than the value that is generally used, it is possible to reduce the downward power penalty in comparison with the conventional method in which the extinction coefficient of the downward optical signal is consistently low and not to allow a sensitivity by which the extinction coefficient of the downstream optical signal becomes smaller than the extinction coefficient required for transmitting the optical signal, thus transmission quality is getting worse rapidly when the length of the light wave devices configuring the downlink even slightly improperly arranged.

Therefore, by instructing to sufficiently increase the extinction coefficient of the downstream optical signal, it is possible to improve the quality and reliability of the downstream transmission and equalize the input downward optical signal in the semiconductor light amplifier sufficiently, thereby improving the quality and reliability of the upstream transmission.

Description of drawings

Figure 1 is a conceptual diagram of a passive optical network with wavelength division multiplexing (WDM-PON) based on a reflective semiconductor optical amplifier (RSOA) that reuses the optical signal.

FIG. 2 is a conceptual diagram of a WDM-PON with time division multiplexing (TDM) based on RSOA that reuses an optical signal.

3 is a view for explaining alignment by the compression effect of optical signals based on RSOA gain saturation.

FIG. 4 is a view for explaining a phenomenon by which an input optical signal is aligned by introducing (injecting) a forward coupling current (FFCI) into an RSOA.

5 illustrates a structure or RSOA in which an active region is divided into two sections for equalizing optical amplitude by dynamically controlling the introduction of a direct current current according to an embodiment of the present invention.

6 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a first embodiment of the present invention.

7 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a second embodiment of the present invention.

FIG. 8 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a third embodiment of the present invention.

FIG. 9 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a first embodiment of the present invention.

10 illustrates a control circuit for introducing a direct current into an RSOA including two active regions, according to a second embodiment of the present invention.

11 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a third embodiment of the present invention.

12 illustrates an RSOA structure including three active regions in order to improve uniformity of an input optical signal according to an embodiment of the present invention.

13 is a configuration diagram of a WDM-PON according to a conventional downlink optical signal reuse method.

Fig. 14 illustrates an optical line terminal (OLT) using a multi-wavelength light source (MWLS) module in a WDM-PON according to an embodiment of the present invention.

FIGS. 15, 16 and 17 are views showing the output spectrum of the MWLS, the bandwidth of the wavelength multiplexing / demultiplexing unit, and the output spectrum that passed through the wavelength multiplexing / demultiplexing unit, in the structure illustrated in FIG.

FIG. 18 illustrates an OLT using a broadband light source module (BLS) module in a WDM-PON, according to an embodiment of the present invention.

FIGS. 19, 20, and 21 are representations showing the output spectrum of the BLS, the bandwidth of the wavelength multiplexing / demultiplexing unit, and the output spectrum that passed through the wavelength multiplexing / demultiplexing unit in the structure illustrated in FIG.

Fig is a configuration diagram of a traditional WDM-PON.

23 is a configuration diagram of a conventional hybrid WDM-TDM-PON.

24 is a view for explaining a reuse phenomenon of an input light wavelength in accordance with an RSOA or SOA (semiconductor optical amplifier) gain saturation characteristic according to an embodiment of the present invention.

25 is a view for explaining a phenomenon of reusing the input light wavelength by introducing a direct current into RSOA or SOA according to an embodiment of the present invention.

FIGS. 26-29 illustrate WDM-PON structures that use a source light (SL) to make the OLT optical transmitter independent of the light wavelength, according to embodiments of the present invention.

30-33 are views for explaining an output spectrum of a source light and an output spectrum that has passed through a WDM demultiplexer when MWLS is used as a source light according to embodiments of the present invention.

Figures 34-36 illustrate MWLS modules according to embodiments of the present invention.

Figs. 37-39 are views for explaining an output spectrum of a BLS, a bandwidth of a WDM multiplexing / demultiplexing module, and an output spectrum that has passed through a WDM multiplexing / demultiplexing module when a BLS is used as a source light according to embodiments of the present invention.

40 illustrates a WDM-PON structure in which an uplink fiber optic line is separated from a downlink transmission fiber optic line between an OLT and a remote node (RN) according to an embodiment of the present invention.

FIG. 41 illustrates a WDM-TDMA-PON structure using a source light to make the OLT optical transmitter independent of the light wavelength, according to an embodiment of the present invention.

Fig. 42 illustrates a WDM-TDMA-PON structure in which an uplink fiber optic line is separated from a downlink fiber optic line in a transmission path between an OLT and an RN, according to an embodiment of the present invention.

FIGS. 43-45 illustrate structures of RSOA-based input light wavelength reusable devices according to embodiments of the present invention.

Figures 46-49 illustrate structures of SOA-based input light wavelength reusable devices according to embodiments of the present invention.

FIG. 50 illustrates the structure of a simplified input light wavelength reusable apparatus utilizing an output signal of a limit amplifier (LA) in order to reuse an optical signal input to the RSOA as transmission light according to an embodiment of the present invention.

Fig. 51 illustrates the structure of a simplified input light wavelength reusable apparatus using a transimpedance amplifier (TIA) output signal in order to reuse an optical signal input to the RSOA as transmission light according to an embodiment of the present invention.

Optimum Mode for Carrying Out the Invention

According to an aspect of the present invention, there is provided a control circuit of a reflective semiconductor optical amplifier (RSOA), including: a splitter dividing the input optical signal into a first signal and a second signal; An RSOA having one active region that reflects a second signal from a reflective face and into which a combined signal from a signal with a polarity opposite to that of the second signal is input and a modulation signal to modulate a second signal reflected from the reflective face to form an output optical signal; a data photodiode converting the first signal into a current signal; a transimpedance amplifier receiving a current signal from the data photodiode and amplifying the current signal into a voltage signal with a polarity opposite to that of the first signal; a radio frequency (RF) amplifier receiving a voltage signal from a transimpedance amplifier and amplifying a voltage signal into an equalization signal suitable to equalize the optical amplitude of the second signal; an RF delay module receiving the equalization signal from the RF amplifier and adjusting the output time of the equalization signal so that the second signal is maximally aligned; and a signal combining module combining an equalization signal with a modulation signal and inputting the result of combining into one active RSOA region.

In addition, the reflective semiconductor optical amplifier has two active regions and includes a semiconductor of the optical amplifier, including a reflective face that reflects the input optical signal; and an optical amplifying semiconductor comprising a back region that is located on the side of the reflective face and into which a signal having a polarity opposite to that of the input optical signal is input, and a front region that is placed on the side opposite to the side of the back region opposing the reflective face, and through which the input optical signal passes through and into which the signal used to modulate the reflected input optical signal from the reflective face is input into the output opt cal signal.

In addition, the semiconductor optical amplifier includes three active regions: a first active region into which a signal with a polarity opposite to that of the input optical signal is introduced to equalize the amplitude of the input optical signal; the second active area; the second active region, which is located on the side of the first active region and into which direct current is introduced to optically amplify the input optical signal passing through the first active region; and a third active region, which is located on the other side of the second active region and into which a signal is input to modulate the input optical signal passing through the second active region into the output optical signal.

In addition, RSOA is an optical amplifier having two active regions, and which contains a reflective face that reflects the input optical signal; and an optical amplifying semiconductor comprising a back region that is located on the side of the reflective face and into which a signal having a polarity opposite to that of the input optical signal is input, and a front region that is placed on the other side of the back region and through which the input optical signal passes and into which a signal is input to modulate the input optical signal reflected from the reflective face into the output optical signal, while the equalization signal transmitted from the first LD A driver is introduced into the rear region RSOA, having two active regions, and wherein the signal for modulating the second signal to the output optical signal is injected into the front region RSOA, having two active regions.

According to another aspect of the present invention, there is provided a downlink optical transmission apparatus using a wavelength independent light source that is used in an optical line terminal of a passive optical network with wavelength division multiplexing (WDM-PON), including: a source light module generating multiwave optical signal; a wavelength multiplexing / demultiplexing module dividing a multiwave optical signal according to wavelengths; an optical transmitting device generating a downward optical signal using an optical signal received from a wavelength multiplexing / demultiplexing unit in response to a plurality of electrical signals received from an external device; and a circulator transmitting the multi-wavelength optical signal to the wavelength multiplexing / demultiplexing unit or transmitting the optical signal output from the wavelength multiplexing / demultiplexing unit to the subscriber side, wherein the wavelength multiplexing / demultiplexing unit combines a plurality of downstream optical signals generated by optical transmitting device, with each other.

According to another aspect of the present invention, there is provided a downlink optical transmission device using a wavelength independent optical source that is used in a passive optical network with wavelength division multiplexing (WDM-PON), including: a source light module generating a broadband optical signal ; a wavelength multiplexing / demultiplexing module dividing a broadband optical signal according to wavelengths; an optical transmitting device generating a downward optical signal using an optical signal received from a wavelength multiplexing / demultiplexing unit in response to a plurality of electrical signals received from an external device; and a circulator transmitting the broadband optical signal to the wavelength multiplexing / demultiplexing unit or transmitting the optical signal output from the wavelength multiplexing / demultiplexing unit to the subscriber side, wherein the wavelength multiplexing / demultiplexing unit combines a plurality of downstream optical signals generated by optical transmitting device, with each other.

According to another aspect of the present invention, there is provided a downlink optical transmission method using a wavelength independent optical source that is used by an optical line terminal (OLT) of a passive optical wavelength division multiplexed network (WDM-PON), including: multi-wavelength generation optical signal using a multi-wavelength light source; division of a multiwave optical signal according to wavelengths; generating a plurality of downstream optical signals with each optical signal received and separated according to wavelengths in response to a plurality of electrical signals received from an external device; and combining the plurality of downstream optical signals with each other and transmitting the result of the combination to the subscriber side via the optical line.

According to another aspect of the present invention, there is provided a downlink optical transmission method using a wavelength independent light source that is used by an optical line terminal (OLT) of a passive optical wavelength division multiplexed network (WDM-PON), including: forming broadband optical signal using a broadband light source (BLS); division of a broadband optical signal according to wavelengths; generating a plurality of downstream optical signals with each optical signal received and separated according to wavelengths in response to a plurality of electrical signals received from an external device; and combining the plurality of downstream optical signals with each other and transmitting the result of the combination to the subscriber side via the optical line.

According to another aspect of the present invention, there is provided an optical line terminal (OLT) using a wavelength independent light source that is used in a passive optical wavelength division multiplexing (WDM-PON) network, including: a protocol processor performing protocol processing a downward electrical signal to be transmitted to the subscriber side, or an upward electrical signal transmitted from the subscriber side; a downlink optical transmission module generating a plurality of downlink optical signals in response to each downlink electric output signal from a protocol processor using a multi-wavelength optical signal or a broadband optical signal and combining a plurality of downlink optical signals with each other and generating a downlink optical WDM signal; a circulator transmitting the downward optical WDM signal to the subscriber side through the optical line; and an uplink optical reception module receiving an uplink optical WDM signal transmitted from the subscriber side through an optical line through a circulator dividing the upstream optical WDM signal according to wavelengths, converting each optical signal into an electrical signal and outputting the electrical signal to a protocol processor.

The present invention provides two embodiments, first and second embodiments, implemented as follows.

The first embodiment provides a structure in which a semiconductor optical amplifier, which is a wavelength independent light source, is used as an optical transmitter of a telephone exchange using a multi-wavelength light source module (MWLS), and determines an output length interval of optical signals output from the module MWLS, and the bandwidth of the demultiplexer wavelength (splitter wavelength) in a passive optical network with multiplexing with division by Line wavelength (WDM-PON) according to the method reusable downlink optical signal.

A second embodiment provides a structure in which a semiconductor optical amplifier, which is a wavelength independent light source, is used as an optical transmitting device in a telephone exchange using a broadband light source module (BLS) in WDM-PON according to a downlink optical reuse method signal.

According to the present invention, a downlink optical transmission device in a telephone exchange demultiplexes optical signals that are output from the MWLS module or BLS module for each WDM channel, and inputs the demultiplexing result into RSOA. Then the RSOA generates an optical signal with respect to each downstream electrical signal that is received from the protocol processor, multiplexes along the wavelength the downstream optical signal generated for each WDM channel by the wavelength multiplexer (wavelength combining module) in the telephone exchange, and transmits the result wavelength division multiplexing to the subscriber side.

According to another aspect of the present invention, there is provided a wavelength division multiplexing (WDM-PON) passive optical network system including: a source light driver that generates the source light, the wavelength interval and the center wavelength of which are adjustable for at least using a single source of light; an optical line terminal (OLT) receiving the source light from the source light shaper, transmitting the downlink optical signal to the WDM-PON subscriber, and receiving the upstream optical signal transmitted from the subscriber; an optical network module (ONU) transmitting an uplink optical signal into which a downlink optical signal received from the OLT is modulated so that the downlink optical signal includes an upstream data stream.

The WDM-PON system further includes a wavelength multiplexing / demultiplexing unit dividing the downlink optical signal transmitted from the OLT according to wavelengths and multiplexing the uplink optical signal transmitted from the ONU according to wavelengths.

The OLT and the wavelength multiplexing / demultiplexing module are connected through one optical fiber to each other.

The source light shaper includes: at least one source of source light forming the source light having a predetermined wavelength; an optical splitter that collects and redistributes the source light generated by at least one source of source light; an optical amplifier amplifying the optical signal output from the optical splitter; and an optical power splitter splitting the amplified optical signal and transmitting the broken optical signal to the OLT.

OLT includes: a protocol OLT processor that performs protocol processing of the downstream data stream to be transmitted to the subscriber side and the upstream data stream transmitted from the subscriber side; a downlink optical transmitter transmitting a downlink optical signal including a downstream data stream generated by modulating the source light to a subscriber side; and an upstream optical receiver receiving an upstream optical signal including an upstream data stream that the subscriber side wants to transmit.

The downstream optical transmitter includes: a downlink optical signal modulator modulating the source light so that the source light includes a downstream data stream; a downlink optical signal multiplexer, a multiplexing downlink optical signal transmitted from a downlink optical signal modulator; a circulator separating the source light signal from the downstream optical signal transmitted from the downstream optical signal multiplexer; and a downlink optical signal amplifier amplifying the downlink optical signal transmitted from the circulator so that the downlink optical signal is transmitted to the ONU.

The upstream optical receiving device includes: an upstream optical signal amplifier amplifying the upstream optical signal to compensate for transmission loss of the upstream optical signal; an uplink optical signal demultiplexer dividing the uplink optical signal transmitted from the uplink optical signal amplifier according to wavelengths; and an uplink optical signal demodulator demodulating the uplink optical signal to extract an uplink data stream included in the uplink optical signal transmitted from the uplink optical demultiplexer.

The WDM-PON system further includes: a control optical signal transmitter transmitting an optical control signal; a control optical signal receiving device receiving a control optical signal after the control optical signal passes through a passive optical network; a communication line monitoring controller controlling the transmission of optical signals of the control optical signal transmitter and the reception of optical signals of the control optical signal receiving device and determining whether the optical fiber connecting the OLT to the ONU is cut and the upstream optical signal is transmitted from the ONU based on the control optical signal; a first splitter transmitting the control optical signal to the optical fiber so that the control optical signal is transmitted in a downward direction; and a second splitter dividing the pilot optical signal after the pilot optical signal passes through the passive optical fiber network to receive the pilot optical signal from the optical fiber.

The control optical signal transmitting device includes: a first frequency converter receiving a control electric signal from a communication line monitoring controller and converting a frequency of a control electric signal using an RF carrier located in a frequency domain that is remote from the baseband; and a control light source module, modulating a control optical signal with a control electric signal whose frequency is converted, and generating a modulated optical signal.

The control light source module includes: an optical switch module receiving an initial light and outputting an optical signal having a specific wavelength; and a reflective semiconductor optical amplifier (RSOA), modulating the optical signal received from the optical switch module using the control electric signal received from the first frequency converter and the control electric signal received from the communication line monitoring controller.

The control light source module includes: an optical signal multiplexing / demultiplexing module, receiving the source light, dividing the source light according to wavelengths and outputting the optical signal; and a reflective semiconductor optical amplifier (RSOA) matrix module modulating an optical signal received from the optical signal multiplexing / demultiplexing module using the control electric signal received from the first frequency converter and the control electric signal received from the communication line monitoring controller.

The receiver of the control optical signals includes: an optical signal converter, receiving a control optical signal of how the control optical signal passes through the PON, and converting the control optical signal into an electrical signal; and a second frequency converter that converts the frequency of the electrical signal received from the optical signal converter into a modulating frequency band.

The source of light includes: an optical amplifier that generates an optical signal; an optical reflection module reflecting an optical signal by varying a reflection coefficient and an optical attenuation coefficient of an optical signal; an optical signal multiplexing / demultiplexing module, receiving an optical signal generated by an optical amplifier, dividing the optical signal according to wavelengths, and transmitting the divided optical signal to the optical reflective module; an optical splitter receiving an optical signal reflected by the optical reflective module, transmitting a portion of the optical signal to the outside, and transmitting the remainder of the optical signal to the optical amplifier; and a circulator transmitting the optical signal generated by the optical amplifier to the optical signal multiplexing / demultiplexing module and transmitting the optical signal reflected by the optical reflective module to the optical splitter.

The OLT and the wavelength multiplexing / demultiplexing unit are connected to each other so that the uplink transmission and downlink transmission, respectively, are performed through a separate optical fiber.

The ONU includes: a protocol processor ONU that performs protocol processing of the downstream data stream to be transmitted to the subscriber side and the upstream data stream transmitted from the subscriber side; an upstream optical transmitter that aligns and optically amplifies the downstream optical signal so as to convert the downstream optical signal to upstream light, modulating the upstream light into an upstream optical signal including the upstream data stream that the subscriber side wants to transmit, and then transmitting the upstream optical signal; a downstream optical receiver receiving a downlink optical signal including a downstream data stream and extracting a downstream data stream; and an optical splitter dividing the downlink optical signal and transmitting the divided downlink optical signal to the upstream optical transmitter and the downlink optical receiver.

The optical transmitting device includes: an optical splitter splitting the downstream optical signal into a first signal and a second signal, and outputting a first signal and a second signal; an LED that converts the first signal into a current signal; a transimpedance amplifier that amplifies the current signal transmitted from the LED and converts the amplified current signal to a voltage signal; a limiter amplifier reinforcing a voltage signal transmitted from a transimpedance amplifier; a first delay module adjusting the phase of the voltage signal outputted or inverted by the limiter so that the second signal is optimally aligned; a circuit And transmitting the output signal of the first delay module through itself when the upstream data stream has a level of "1", and not allowing the output signal of the first delay module through itself when the upstream data stream has a level of "0"; a second delay module that controls the phase of the output signal output from the AND circuit and the phase of the upstream optical signal so that the phase of the output signal output from the AND circuit is equal to the phase of the upstream optical signal; a first LD driver modulating an output signal output from the AND circuit to a modulated signal; a second LD driver modulating an output signal output from the second delay module into a modulated signal; and a reflective semiconductor optical amplifier (RSOA) equalizing the second signal with a modulated signal output from the first LD driver, and modulating the second signal with an upward optical signal when the second signal is reflected from the reflective face using a modulated signal output from the second LD drivers.

The WDM-PON system further includes: a first circulator propagating a second RSOA signal, receiving a balanced signal from RSOA and dividing the aligned signal to the outside, an external modulator receiving a aligned signal from the first circulator and modulating the aligned signal into an upstream optical signal using the output signal from second LD driver; and a second circulator receiving an upward optical signal from an external modulator and transmitting an upward optical signal in an upward direction, wherein the RSOA equalizes the second signal with a signal output from the first LD driver.

RSOA includes two active regions having a rear region for aligning the second signal with a signal received from the first LD driver, and a front region for transmitting the second signal through the rear region and reflecting the second signal from the reflection face and modulating the reflected second signal to the upstream optical signal using a signal received from the second LD driver.

An optical transmitting device includes: an optical splitter dividing the downstream optical signal into a first signal and a second signal and outputting a first signal and a second signal; an LED that converts the first signal into a current signal; a transimpedance amplifier that amplifies the current signal transmitted from the LED and converts the amplified current signal to a voltage signal; a limiter amplifier reinforcing a voltage signal transmitted from a transimpedance amplifier; a first delay module that adjusts the phase of the voltage signal output from or inverted by the limiter so that the second signal is optimally aligned; an AND circuit that passes the output signal of the first delay module through itself when the upstream data stream has level 1, and does not allow the output signal of the first delay module through itself when the upstream data stream has level 0; a second delay module that controls the phase of the output signal output from the AND circuit and the phase of the upstream optical signal so that the phase of the signal output from the AND circuit is equal to the phase of the upstream optical signal; a first LD driver converting the signal output from the AND circuit to a modulated signal; a second LD driver module converting a signal output from the second delay module into a modulated signal; a semiconductor optical amplifier (SOA) equalizing the second signal with a combined signal from a signal output from the first LD driver and a signal output from the second LD driver, and modulating the aligned signal into an upward optical signal; and a circulator dividing the upstream optical signal so that the upstream optical signal is transmitted in the upstream direction.

The WDM-PON system further includes an external modulator receiving the second signal aligned by SOA and modulating the second signal into the upstream optical signal using the output signal from the second LD driver, wherein the SOA equalizes the second signal using the signal output from the first LD drivers.

An SOA includes two active regions having a front region for aligning the second signal using a signal output from the first LD driver, and a rear region for modulating a second signal aligned by the front region into an upward optical signal using the output signal from the second LD drivers.

An SOA includes three active regions having a front region for equalizing a second signal using a signal output from a first LD driver, an intermediate region for optically amplifying a second signal aligned by a front region, and a rear region for modulating a second signal optically amplified by intermediate region, in the upward optical signal.

An optical transmitting device includes: an optical splitter dividing the downstream optical signal into a first signal and a second signal and outputting a first signal and a second signal; the part of the LED that converts the first signal into a current signal; a transimpedance amplifier that amplifies the current signal transmitted from the LED and converts the amplified current signal into a voltage signal; a limit amplifier re-amplifying a voltage signal transmitted by a transimpedance amplifier; a delay module that regulates the phase of the voltage signal output from or inverted by the amplifier-limiter so that the second signal is optimally aligned; An RF amplifier that controls the signal transmitted through the delay module so that the size of the second signal is optimally aligned; LD driver that converts the upstream signal into a modulated signal; RSOA equalizing the second signal with a signal output from the RF amplifier, and modulating the aligned second signal with an upward optical signal using a signal output from the LD driver when the second signal is reflected from the reflective face.

The delay module adjusts the phase of the voltage signal output from or inverted by the transimpedance amplifier without passing through the limit amplifier so that the second signal is optimally aligned.

An embodiment of the invention

The following describes in detail preferred embodiments of the present invention with reference to the accompanying drawings.

Figure 1 is a conceptual diagram of a passive optical network with wavelength division multiplexing (WDM-PON) based on a reflective semiconductor optical amplifier (RSOA) that reuses optical signals. Referring to FIG. 1, a WDM-PON includes a central station (CO) 101, an optical fiber line 102, a remote node (RN) 103, and a plurality of optical network terminals (ONT) 104.

The central station 101 includes an optical source module for transmitting a downstream data stream, a receiver for receiving an upstream data stream and an optical multiplexing / demultiplexing (MUX / DMUX) module for multiplexing / demultiplexing the light wavelengths.

The remote node 103 includes an optical multiplexing / demultiplexing module (MUX / DMUX), consisting of a single filter of types of waves on the array in the waveguide (AWG) or thin-film filter (TFF). If the multiplexed downlink optical signals are received in the optical multiplexing / demultiplexing module of the remote node RN 103, the downlink optical signals are divided according to their wavelengths and transmitted to the ONT 104 via an optical fiber line.

Each ONT 104 includes RSOA, an optical receiver, and a splitter. Elements can be ordered individually or can be integrated on the same substrate. The splitter distributes the downstream optical power of the downstream optical signal, which is received via the fiber optic line, to the RSOA and the optical receiving device, taking into account the budget of optical power and the saturation of the amplification of the downstream optical power. The optical receiver receives the corresponding downstream optical signal D ₁ (where i = 1 ~ N), and the RSOA re-modulates the corresponding input downstream optical signal D ₁ into the upstream optical signal U _i (where i = 1 ~ N) and transmits the remodulated upstream optical signal U _i to the central station 101 (via the remote controller 103?).

The upstream optical signal U _{i is} multiplexed by the optical multiplexing / demultiplexing module of the remote node 103 and then transmitted to the central station 101 via the optical fiber line 102. The upstream optical signal U _i input to the central station 101 is demultiplexed by the optical multiplexing / demultiplexing unit in the central station 101 and then transmitted to the optical receiver for each channel (or for each wavelength).

The optical receiver finally receives the upstream optical signal U _N.

FIG. 2 is a conceptual diagram of an RSOA-based WDM-PON time division multiplexing (TDM) system that reuses optical signals. Referring to FIG. 2, a WDM-PON-TDM system includes a central station (CO) 201, an optical fiber line 202, a remote node (RN) 203, and a plurality of optical network terminals (ONT) 204, wherein the remote node 203 includes splitter 205. Elements 201-204 have the same roles and functions as elements 101-104, illustrated in FIG.

A 1: M split ratio of splitter 205 is determined taking into account the power budget of the entire optical link and the gain saturation RSOA for the input power. If the downstream optical signals are received by the optical multiplexing / demultiplexing module, the downstream optical signals are divided according to wavelengths by the optical multiplexing / demultiplexing module, and each downstream optical signal is transmitted according to its wavelength M to the subscribers through splitter 205. Thus, if the multiplexing ratio is divided the wavelength is 1: N, the total number of subscribers that can be served is significantly increased to NxM . Each downstream optical signal that is transmitted through a splitter 205 and an optical fiber line 202 is input to the RSOA and the optical receiver via a splitter. The downstream optical signal input to the RSOA is re-modulated into the upstream optical signal, and the optical receiver recovers the downstream optical signal. The downstream optical signal input to the optical receiving device includes information that must be transmitted to a plurality of subscribers and multiplexed by a time division method, and the optical receiving device extracts only its relevant information from the information. The upstream optical signal is transmitted during its assigned time slot to the central station 201 via RSOA so that the upstream optical signal does not conflict with the upstream optical signals transmitted from the remaining (M-1) subscribers. The upstream optical signals that are output from the RSOA and transmitted through channels to a maximum of M subscribers using TDM are combined using a splitter 205 of the remote node 203, then are wavelength-multiplexed by the optical multiplexing / demultiplexing module and then input to the optical receiving device of the central station 201 according to wavelengths. Here, the optical receiving device is an optical packet receiving device, and it must have a sufficient dynamic range to compensate for the difference in optical power between the upstream optical signals of M subscribers that are connected to splitter 205.

3 is a view for explaining alignment by the compression effect of optical signals based on RSOA gain saturation. When the downstream optical signal is introduced into the region where the gain is saturated (that is, when the input optical power is greater than the optical power at which the gain is saturated), the gain is not sufficiently implemented at level “1”, since the gain is saturated at level “1” while the amplification is carried out to a relatively large extent at the level of "0". As a result, the difference ΔPin between the level “1” and the level “0” of the downstream optical signal decreases to ΔPout, i.e. ΔPin> ΔPout. This phenomenon is called the amplitude compression effect. However, the downstream optical signal, which is not fully compressed, has a residual amplitude ΔPout, and if the downstream optical signal is modulated directly into the upstream data stream in this state, the level “1” of the upstream optical signal becomes thick, i.e. ΔPin → ΔP1. The quality of the upstream transmission degrades as level 1 becomes thick. In particular, if the thickness of level “1” exceeds a certain value, the quality of the upstream transmission deteriorates rapidly and, accordingly, the power penalty increases rapidly. Therefore, it is necessary to significantly reduce the extinction coefficient of the downstream optical signal. However, if the extinction coefficient of the downlink optical signal is small, the extinction coefficient decreases rapidly, and the transmission quality deteriorates rapidly when the light wavelengths of the devices constituting the downlink are even slightly improperly arranged.

Figure 4 illustrates that the optical signal is aligned by dynamically controlling the injection of the direct current. During the period of level “1” of the input optical signal, if the amount of current injection decreases compared to the value in the period of level “1” of the input optical signal, i.e. if I1 <I0, the gain decreases. Accordingly, the power difference between the level “1” and the level “0” of the input optical signal can be reduced. Therefore, alignment is possible with a low input optical power regardless of the saturation characteristic of the RSOA optical gain, and thus the budget of the optical power of the optical communication line is increased. In addition, the extinction coefficient of the downstream optical signal can be adjusted to a relatively high value so that the penalty on the power of the downstream transmission can be reduced. Moreover, the phenomenon in which the extinction coefficient decreases rapidly and the transmission quality deteriorates rapidly, even when the light wavelengths of the devices constituting the downlink are slightly incorrectly arranged, can be mitigated. In addition, the quality of the uplink transmission can be improved by reducing the thickness of the “1” level of the upstream optical signal.

5 illustrates a structure or RSOA in which an active region is divided into two sections for equalizing optical amplitude by dynamically controlling the introduction of a direct current current according to an embodiment of the present invention. Referring to FIG. 5, the RSOA includes a front region 502 (SECTION 2), a rear region 501 (SECTION 1), and a spot size conversion region (SCC) 503, which can be included if necessary.

A current for modulating the upstream optical signal is input to the front region 502. The front region 502 takes on the modulation property of the input optical signal and provides a current having a polarity opposite to that of the input optical signal to the rear region 501. The carrier density and optical power gain of the rear region 501 are changed according to the introduced current so that the gain decreases at the level “1” of the input optical signal and increases at the level “0”. Accordingly, the extinction coefficient of the input optical signal can ultimately be significantly reduced.

6 illustrates a control circuit for introducing a direct current into an RSOA including one active region, according to an embodiment of the present invention. Referring to FIG. 6, the control circuit includes an optical coupler 601, a data photodiode (dPD) 602, a transimpedance amplifier (TIA) 603, a limit amplifier (LA) 604, a first RF delay 605, a second RF delay 608, and 606 AND , the first LD driver (LDD I) 607, the second LD driver (LDD II) 609, a signal combining module 610, RSOA 60, and an optical delay line 611.

The downstream optical signal transmitted from the telephone exchange is split by the optical splitter 601 so that the downstream optical signal region is input to the RSOA 600 and the other downstream optical signal region is input to the dPD 602. The downstream optical signal input to the dPD 602 is converted to a signal current and is output, and then amplified by a transimpedance amplifier 603 to be converted into a voltage signal. The transimpedance amplifier 603 transmits the voltage signal to the limit amplifier 604. The limit amplifier 604 re-amplifies the voltage signal.

One of the outputs of the amplifier-limiter 604 is connected to the downstream signal processor, and the other outputs are connected to the RF delay 605. The output of the RF delay 605 is transmitted to the I circuit 605.

In the meantime, some of the upstream input data signals are input to the 606 I circuit.

Circuit 606 And passes the output signal of the first RF delay 605 through itself when the received upstream data signal has a level of “1”, and does not allow the output of the RF delay 605 through itself when the received upstream signal has a level of “0”. The output of the AND circuit 606 is converted to a current signal by the first LD driver 607 and then output.

The remainder of the signals of the upstream input data stream is converted into a current signal by a second LD driver 609 and combined with a bias current and then output. The output of the first LD driver 607 for providing direct current and the output signal LDD 609 for providing upstream current are combined with each other via a signal combining module 610 and then input to RSOA 600.

In order to optimally align the optical signal input to the RSOA, the direct signal phase and the phase of the downstream optical signal input to the RSOA 600 are adjusted to the optimum state by the first RF delay 605, while the phase of the upstream signal input to the And circuit and the phase of the upward signal input to the RSOA 600 are adjusted to the optimum state by the second RF delay 608. Meanwhile, the optical delay line 611 operates to compensate for the electrical delay by the RF delay I 605.

7 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a second embodiment of the present invention. Referring to FIG. 7, the structure of the control circuit is the same as the structure of the control circuit illustrated in FIG. 6, except that the RF amplifier 712 is added before the RF delay 705 and the And circuit 606 is omitted to adjust signal sizes output from the amplifier-limiter 704, so that can be obtained optimal uniformity.

The output of the RF delay 705 is combined with the output of the LD driver 709 in the signal combining module 710 and then input to the RSOA 700 to modulate it in the upstream data stream. Accordingly, the current introduced into the RSOA 700 has a format in which the direct current, inversely proportional to the intensity of the modulated downstream optical signal, overlaps the current at the output of the LD driver 709.

FIG. 8 illustrates a control circuit for introducing a direct current into an RSOA including one active region according to a third embodiment of the present invention. Referring to FIG. 8, the structure of the control circuit is the same as the structure of the control circuit illustrated in FIG. 7, except that one of the output signals of the transimpedance amplifier 703, which is in front of the limiting amplifier 704, is used as a signal direct current

FIG. 9 illustrates a control circuit for introducing a direct coupling current into an RSOA including two active regions, according to a first embodiment of the present invention. The structure of the control circuit illustrated in FIG. 9 is the same as the structure of the control circuit illustrated in FIG. 6, except that the RSOA 600 of FIG. 6 has one active region, while the RSOA of FIG. 8 has two active regions are the rear and front regions, while the rear region is located on the side of the reflective face and receives a signal having a polarity opposite to the polarity of the input optical signal, and the front region is located on the side opposite to the side of the rear region opposing the reflective audio, transmits an input optical signal to the rear region and modulates the input optical signal reflected by the reflection faces in the output optical signal.

10 illustrates a control circuit for introducing a direct current into an RSOA including two active regions, according to a second embodiment of the present invention. The structure of the control circuit illustrated in FIG. 10 is similar to the structure of the control circuit illustrated in FIG. 7.

11 is a control circuit for introducing a direct current into the RSOA, including two active areas, according to a third embodiment of the present invention. The structure of the control circuit illustrated in FIG. 11 is similar to the structure of the control circuit illustrated in FIG.

12 is a view for explaining an SOA including three active areas to improve uniformity of an input optical signal according to an embodiment of the present invention. Referring to FIG. 12, an SOA includes a front region 1210, an intermediate region 1220, a rear region 1230, and an SSC region 1240.

The SOA has a structure including three active regions: a front region 1210 into which the downstream optical signal is input, an intermediate region 1220 to amplify the downstream optical signal, and a rear region 1230 to modulate the downstream optical signal to the output optical signal. A current for modulating the upstream optical signal is introduced into the rear region 1230. The intermediate region 1220 receives a direct current and a modulation characteristic of the input optical signal and injects them with a current having a polarity opposite to that of the current for modulation in the front region 1210.

The carrier density and optical power gain of the front region 1210 are dependent on the input current. If the input optical signal has a level of "1", the front region 1210 lowers the gain, and if the input optical signal has a level of "0", the front region 1210 increases the gain. Accordingly, the extinction coefficient of the input optical signal can be significantly reduced.

SSC 1240 can be used to enhance the combining effect between the fiber optic link and the SOA.

FIG. 14 is a block diagram of an optical line terminal (OLT) 1300 using a multi-wavelength light source (MWLS) 1401 in a WDM-PON, according to an embodiment of the present invention. The OLT 1300 generates a downstream optical signal using the MWLS 1401.

The OLT 1300, as illustrated in FIG. 14, includes a protocol processor 1301, a downlink optical transmission module 1400, an optical circulator 1304, and an uplink reception module 1410. The corresponding elements will be described below.

First, the protocol processor 1301 processes the downstream electrical signal to be transmitted to the subscriber side or the upstream electrical signal that is transmitted to the subscriber side and performs the same function as the protocol processor illustrated in FIG. 13.

The downlink optical transmission module 1400, as illustrated in FIG. 14, includes a multi-wavelength light source (MWLS) 1401, an optical circulator 1402, a wavelength multiplexing / demultiplexing module 1403, and a plurality of optical transmitters 1404.

The OLT 1300 illustrated in FIG. 14 is implemented by adding MWLS 1401 and the optical circulator 1402 to the OLT 1300 illustrated in FIG. 13 and using a wavelength independent semiconductor amplifier as the optical transmitting device 1404. Thus, the optical transmitting device 1404 is the same wavelength independent semiconductor optical amplifier as in the ONU 1330 optical transmitting device 1332, and not a fixed wavelength optical transmitting device 1302, illustrated 13 bathrooms.

The wavelength multiplexing / demultiplexing unit 1403 acts as a wavelength demultiplexer corresponding to a wavelength splitter when the multi-wavelength optical signal is received from MWLS 1401 through the optical circulator 1402, and acts as a wavelength multiplexer when the multi-wavelength optical signal is received from optical transmitting device 1404. The wavelength multiplexing / demultiplexing module 1403 illustrated in FIG. 8 also works in the same way .

The operation of the OLT 1300 is described below with reference to FIGS. 14-17.

If the multi-wavelength optical signal is output from the MWS module 1401, the optical circulator 1402 transmits the multi-wavelength optical signal to the wavelength multiplexing / demultiplexing module 1403.

Then, the wavelength multiplexing / demultiplexing unit 1403 acts as a wavelength splitter, as illustrated in FIG. Thus, the wavelength multiplexing / demultiplexing unit 1403 divides the multiwave optical signal according to the wavelengths and outputs each optical signal to a corresponding optical transmitting device 1404 (see FIG. 17).

Further, if each optical transmitter 1404 receives a downstream electrical signal from a protocol processor 1301, the optical transmitter 1404 generates and outputs a downstream optical signal using a downstream electrical signal.

The wavelength multiplexing / demultiplexing unit 1403 combines downlink optical signals output from respective optical transmitters 1404 with each other and generates a downlink optical WDM signal. Thus, the wavelength multiplexing / demultiplexing unit 1403 acts as a wavelength multiplexer.

The downstream WDM optical signal, which is combined in this way, is transmitted to the ONU side via the optical circulator 1402 or 1304 corresponding to the branch module.

The method for transmitting a downlink optical signal to an OLT described above is explained in detail with reference to FIGS. 15, 16 and 17 below.

Meanwhile, the uplink light receiving unit 1410 from the OLT 1300 includes a wavelength demultiplexer 1305 and a plurality of optical PD receivers from # 1 to PD #N 1306. The uplink receiving unit 1410 divides the uplink optical WDM signal (transmitted from the ONU side) received through the optical circulator 1304 according to the wavelengths and converts each optical signal into an electrical signal and outputs the resulting electrical signal to a protocol processor 1301. Thus, the function of the upstream light receiving unit 1410 is described above with with reference to FIG. 13.

In addition, the ONU 1330 also has the same function as described above in FIG. 13, and therefore, a detailed description thereof is omitted.

15, 16 and 17 are representations for explaining the output spectrum of the MWLS 1401, the bandwidth of the wavelength multiplexing / demultiplexing unit 1403, and the output spectrum that has passed through the wavelength multiplexing / demultiplexing unit 1403 in the OLT 1300 illustrated in FIG. .fourteen.

Thus, FIG. 15 illustrates an output spectrum (spectrum of a multi-wavelength optical signal) of MWLS 1401, FIG. 16 illustrates the bandwidth of a wavelength multiplexing / demultiplexing unit 1403 corresponding to a wavelength splitter, and FIG. 17 illustrates an output spectrum for a particular channel. that passes through the wavelength multiplexing / demultiplexing unit 1403, serving as a wavelength divider.

The optical spectrum output from the MWLS 1401 module is output with multiple wavelengths, and the output optical power of the wavelengths are uniform, with the output optical power of each wavelength being within 5 dBm.

The bandwidth range of the BW _MWS 1500 of the multiwave optical signal that is output from the MWLS module 1401 satisfies Equation 1 when the number of available channels is N and the channel span is Δλ _WDM 1501. Thus, Equation 1 represents the relationship between N x Δλ _WDM and Bandwidth range BW _MWS of the optical output signal MWLS 1401:

BW _MWS ≤N × Δλ _WDM .

Meanwhile, as illustrated in FIG. 16, the relationship between the WDM channel bandwidth Δλ _passband 1602 of the multiplexing module 1403 / demultiplexing and the output wavelength interval Δλ of the _MWS 1501 MWLS 1401 satisfies equation 2:

Δλ _MWS ≤ Δλ _passband

When equations 1 and 2 are satisfied, after the optical output signal MWLS 1401 passes through the wavelength multiplexing / demultiplexing unit 1403, the resulting spectrum is shown in FIG.

The spectrum that passed through the wavelength multiplexing / demultiplexing unit 1403 includes an output wavelength of MWLS 1401, which exists in the channel bandwidth Δλ _passband 1701 of the wavelength multiplexing / demultiplexing unit 1403. Thus, FIG. 17 illustrates a case where three output wavelengths of an MWLS module 1401 exist in a channel bandwidth Δλ _passband 1701 of a wavelength division multiplexing / demultiplexing module 1403.

When multiple wavelengths exist in the WDM channel under the aforementioned condition, a power penalty may occur in the WDM channel due to distortion of the downstream optical signal, which is caused by branching of the optical fiber line when the transmission distance is significant. Therefore, when the wavelength multiplexing / demultiplexing unit 1403 has a wavelength interval of 200 GHz, it is preferable that the following equation 3 is satisfied:

Δλ _passband ≤ 1.2 nm

At least one light wavelength may exist within a bandwidth range, such as in Equation 3. Here, it is preferred that two or more light wavelengths exist within a bandwidth range.

The MWLS 1401 can be configured with various structures. For example, the MWLS 1401 may be a structure including an erbium doped fiber ring laser, a semiconductor ring laser, a DFB-LB matrix, and a wavelength multiplexer.

FIG. 18 is a block diagram of an OLT using BLS in a WDM-PON according to an embodiment of the present invention.

The OLT 1300, as illustrated in FIG. 18, includes a protocol processor 1301, a downlink optical transmission module 1800, an optical circulator 130, and an uplink optical reception module 1810, wherein the elements, with the exception of the downlink optical transmission module 1800, are the same as corresponding elements illustrated in FIG.

Here, the downlink optical transmission module 1800, as illustrated in FIG. 18, includes a broadband light source (BLS) 1801, an optical circulator 1802, a wavelength multiplexing / demultiplexing module 1803, and a plurality of optical transmitting devices 1804. Moreover, each optical transmitting device 1804 may be a wavelength independent semiconductor optical amplifier.

To summarize, the main difference between the OLT 1300 illustrated in FIG. 18 and the OLT 1300 illustrated in FIG. 14 is that the MWLS 1401 is replaced with BLS 1801. The rest of the OLT 1300 structure illustrated in FIG. 18, in the entity is the same as the structure of the OLT 1300 illustrated in FIG. 14, and accordingly, a detailed description thereof is omitted.

19, 20, and 21 are representations for explaining the output spectrum of the BLS module 1801, the bandwidth of the wavelength multiplexing / demultiplexing module 1803, and the output spectrum that has passed through the wavelength multiplexing / demultiplexing module 1803 in the OLT 1300 illustrated in Fig. 18.

Thus, FIG. 19 represents the output spectrum (spectrum of the broadband light signal) of BLS 1801, FIG. 20 represents the bandwidth of the wavelength multiplexing / demultiplexing unit 1803, which acts as a wavelength splitter, and FIG. 21 represents the output spectrum for a particular channel that has passed through a wavelength multiplexing / demultiplexing module 1803, which acts as a wavelength divider.

As illustrated in FIG. 19, the output bandwidth of the BW _BLS 1900 of the BLS module 1801 must satisfy equation 4 when the number of available WDM-PON channels is N and the channel span is Δλ _WDM 2001:

BW _BLS ≥N × M _WDM .

When equation 4 is satisfied, the spectrum formed after the optical output signal BLS 1801 has passed through the wavelength multiplexing / demultiplexing unit 1803 is shown in FIG. 21, in which the channel bandwidth Δλ _{passband is} designated 2101.

The passband of the optical signal that has passed through the splitter at the wavelength is determined by the passband width Δλ _passband 2002 of the wavelength division multiplexing / demultiplexing unit 1803, as illustrated in FIG. In the case of transmission over long-distance lines, Equation 3 must be satisfied in order to reduce the penalty caused by branching the optical fiber line.

BLS 1801 can be configured with many structures. For example, the BLS 1801 includes a semiconductor superluminescent LED (SLD), a light source with amplified spontaneous emission (ASE) through an erbium doped fiber amplifier, a semiconductor optical amplifier, an ASE light source, etc.

22 is a configuration diagram illustrating a conventional WDM-PON. Referring to FIG. 22, the WDM-PON includes OLT, RN, and ONU.

An OLT includes a plurality of Rx receivers, a plurality of Tx transmitters, a WDM multiplexer (MUX) for multiplexing a plurality of light wavelengths, and a WDM demultiplexer (DeMUX) for demultiplexing a plurality of light wavelengths.

The RN includes a WDM multiplexer (MUX) for multiplexing a plurality of light wavelengths that are received from an ONU, and a WDM demultiplexer (DeMUX) for demultiplexing a plurality of light wavelengths that are received from an OLT.

An ONU includes a plurality of Rx receivers for receiving downstream optical signals, a plurality of Tx transmitters for transmitting upstream optical signals, and an optical splitter for dividing the optical signal received from RN and sending some of the optical signals to Rx receivers and other optical parts signals to transmitters Tx.

23 is a configuration diagram illustrating a conventional WDM-TDM-PON. Referring to FIG. 23, the WDM-TDM-PON includes OLT, RN, and ONU, similar to WDM-PON.

An OLT includes multiple Rx receivers, multiple Tx transmitters, a WDM multiplexer (MUX) for multiplexing multiple light wavelengths, and a WDM demultiplexer (DeMUX) for demultiplexing multiple light wavelengths, similar to WDM-PON.

The difference between WDM-TDM-PON and WDM-PON is that packet mode receivers are used in the WDM-TDM-PON, because upstream optical packets that are received from the ONU have a packet response due to the application of the TDMA method.

The RN further includes a WDM multiplexer (MUX) for multiplexing a plurality of light wavelengths received from an ONU, a WDM demultiplexer (DeMUX) for demultiplexing a plurality of light wavelengths received from an OLT, and an optical power splitter to enable multiple subscribers to share light wavelength.

An ONU includes a plurality of Rx receivers for receiving downstream optical signals, a plurality of Tx transmitters for transmitting upstream optical signals, and an optical splitter for dividing the optical signals received from RN and sending part of the optical signals to Rx receivers and another part of the optical signals to Tx transmitters, as in WDM-PON.

The difference between WDM-TDM-PON and WDM-PON is that burst mode transmitters are used in the WDM-TDM-PON, since the ONU can transmit an optical signal only for a predetermined time.

24 is a view for explaining a reuse phenomenon of an input light wavelength in accordance with an RSOA or SOA gain saturation characteristic according to an embodiment of the present invention.

If the downstream optical signal is introduced into the gain-saturated region (that is, if the power of the input optical signal is greater than the optical power at which the (R) SOA gain is saturated), level “1” of the downward optical signal cannot receive the gain sufficiently in saturated gain state, while the level “0” of the downstream optical signal takes a relatively large gain, the difference between the level “1” and the level “0” of the downstream optical signal decreases to ΔPout.

Thus, ΔPin> ΔPout. This phenomenon is called the amplitude compression effect. However, since an optical signal that is not sufficiently compressed has a predetermined value ΔPout, when the optical signal is directly modulated into the upstream data stream in this state, ΔPout is reflected in the thickness P1 of level “1” of the modulated optical signal. The greater the thickness ΔP1 of level “1” becomes, the lower the quality of the upstream transmission becomes. In particular, if the thickness of the level “1” exceeds a predetermined thickness, the quality of the upstream transmission deteriorates sharply and the power penalty increases. Accordingly, in order to eliminate the problem, the extinction coefficient of the downstream optical signal should be significantly reduced.

Meanwhile, when the extinction coefficient of the downlink optical signal is low, a sensitivity appears, due to which the extinction coefficient decreases sharply, and thus the transmission quality deteriorates sharply when the light wavelengths from the devices constituting the downlink are even slightly improperly arranged, and accordingly , downlink reliability is deteriorating.

25 is a view for explaining a reuse phenomenon of an input light wavelength by a direct current in a (R) SOA according to an embodiment of the present invention.

Although the input optical signal has a level of "1", the gain decreases during the period of a level of "1" by reducing the amount of current that is input, compared to when the input optical signal has a level of "0". Accordingly, the power difference (ER) between the level “1” and the level “0” of the input optical signal can be aligned.

Accordingly, since the wavelength of the input optics can be reused even with a low input optical power at which gain saturation does not occur, the budget of the optical power of the optical communication line increases, the extinction coefficient of the downstream optical signal can be adjusted to a relatively high value, and thus the downlink power penalty can be reduced. In addition, it is possible to reduce the phenomenon by which the extinction coefficient decreases sharply, and thus the transmission quality deteriorates sharply when the light wavelengths from the devices constituting the downlink are even slightly improperly arranged. By reducing the thickness of the “1” layer, the quality of the upstream transmission can be improved.

26 to 29 are views for explaining a WDM-PON structure using a source light (SL) in order to make the OLT 1610 optical transmitter independent of the light wavelength, according to an embodiment of the present invention.

FIG. 26 illustrates a WDM-PON structure that uses a light wavelength reuse method for transmitting an upstream data stream using a source light to realize an OLT 2610 that is independent of the light wavelength and reusing a downlink optical signal as an upward light. to implement the ONU 2620, which is independent of the light wavelength.

The transmission path between the OLT 2610 and RN 2630 is connected via a single fiber optic line. Referring to FIG. 26, the WDM-PON structure includes an OLT 2610, a source light transmitting unit 2600, an RN 2630, and an ONU 2620.

The OLT 2610 includes an OLT protocol processor 2615, a plurality of functional modules for downlink optical transmission, a plurality of modules for receiving uplink light, a circulator 2619 for separating uplink and downlink optical signals from each other, and a source light transmitting unit 2600. The relevant items are described below.

Firstly, the OLT protocol processor 2615 performs the function of protocol processing for the downstream electrical signal to be transmitted to the subscriber side and the upstream electrical signal to be transmitted from the subscriber side.

Each downlink optical transmission functional module includes a plurality of downlink optical transmission modules 2612, a WDM (MUX) 2611 multiplexer, a circulator 2616 for separating the source light from the downstream optical signal, and a downlink optical signal amplifier 2617.

Each upstream optical reception function module includes a plurality of optical reception modules 2613, a WDM demultiplexer (DeMUX) 2614, and an upstream optical amplifier 2618.

The operation of the OLT 2610 is described below.

The source light that is transmitted from the source light transmitting unit 2600 is input to the WDM multiplexer 2611 (MUX) through a circulator 2616. In the WDM multiplexer 2611, the source light is divided according to wavelengths, and each divided source light is input to a corresponding transmitting device 2612. Transmitter 2612 Includes an optically independent optical module.

The source light, which is introduced into the optically independent optical module, is amplified and modulated into a downstream data stream, which is received from the protocol processor 2615, and then output from the transmitting device 2612. The optical signal output from the transmitting device 2612 contains a downward data stream and is input into Multiplexer 2611 WDM.

Optical signals output from a plurality of transmitters 2612 are wavelength-multiplexed by WDM MUX 2611, pass through a circulator 2616 to separate the source light from the downstream optical signal, amplified appropriately by an optical amplifier 2617, and then introduced into the fiber optic transmission line through the circulator 2619 for separating upstream optical signals and downstream optical signals.

In the meantime, the upward optical signal transmitted from the ONU 2620 is input to the light receiving function module through the optical circulator 2619, amplified by the optical amplifier 2618, separated according to the wavelengths in the WDM 2614 demultiplexer, and then input to the corresponding receiving device 2613.

A receiver 2613 converts the optical signal into an electrical signal, recovers the electrical data from the electrical signal, and then outputs the reconstructed data to the OLT protocol processor 2615.

In the meantime, the OLT 2610 includes an L-Tx 2660 for transmitting an optical signal for monitoring an optical fiber breakage or determining the operating mode of a transmitting device 2622, an L-Rx 2670 for receiving an optical signal for monitoring, and a communication line monitoring control module (LMC) 2680 for control the reception and transmission of the optical signal for monitoring and transmitting information obtained from the optical signal for monitoring to the protocol processor 2615 OLT or receiving and processing a control signal from the protocol processor 2615 OLT.

In addition, the OLT 2610 includes WDM splitters 2640 and 2650 for transmitting the optical monitoring signal through the fiber link in the downstream direction or receiving the optical monitoring signal from the optical fiber.

The source light transmission module 2600 includes a plurality of types of source light (SL) 2601, an nxm combining optical module 2602 (n and m are natural numbers) for collecting and distributing a plurality of types of source light, an optical amplifier 2603 for amplifying an output optical signal from an optical an nxm combining unit 2602 and an optical splitter 2604 for distributing the source light to the plurality of OLTs 2610.

The operation of the source light transmitting unit 2600 is described below.

Many SL 2601 (types of source light) can have different wavelength plans relative to wavelength and center wavelength intervals. If the initial wavelengths of the types of the source light differ from each other, when the types of the source light have the same wavelength interval, the source light having narrower intervals of the wavelength can be obtained by connecting multiple SL 2601 using a splitter 2602. The method can be called interleaving wavelengths.

The types of source light that pass through the coupler 2602 are amplified by an optical amplifier 2603 so that they have the proper optical power, and then introduced into the 1xn splitter 2604. Splitter 2604 1xn splits the source light according to n light intensities and outputs each source light to a corresponding OLT 2610.

RN 2630 includes a WDM Multiplexing / Demultiplexing Unit (MUX / DeMUX) 2631. A WDM Multiplexing / Demultiplexing Unit 2631 acts as a WDM demultiplexer when receiving a downstream signal so that the downstream signal is separated according to wavelengths and acts as a WDM multiplexer when receiving the upward signal so that the light wavelengths are multiplexed and transmitted to the OLT 2610.

The ONU 2620 includes an optical combiner 2621, an optical transmitter 2622, an optical receiver 2623, and an ONU protocol processor 2624.

The operation of the ONU 2620 is described below.

The optical monitoring module 2621 divides the power of the downstream optical signal transmitted from the WDM 2630 demultiplexer so that part of the power of the downstream optical signal is transmitted to the optical receiver 2623 to restore it to the downstream data stream, and the remaining part of the power of the downstream optical signal is input to the optical transmitter 2622.

The downstream optical signal input to the optical transmitter 2622 is converted to a signal that can be reused as rising light through alignment and optical amplification, and then the reused light is converted to the upward optical signal through an electrical signal that is transmitted from the protocol processor 2624 is an ONU and contains an upstream data stream and is then output from the optical transmitting device 2622. Since the optical transmitting device 2622 An ONU 2620 can use light wavelengths that are included within a predetermined wavelength bandwidth, without regard to their wavelength, by using RSOA or SOA, the same type of optical transmitter 2622 can receive all WDM channels.

FIG. 27 shows a detailed structure of the L-Tx 2660, L-Rx 2670, and LMC 2680, which are included in the OLT 2610 to determine a fiber break between the OLT 2610 and the ONU 2620 or the operating mode of the optical transmitting device 2622 of the ONU 2620.

The LMC 2680 receives a control signal regarding monitoring the status of the optical link from the protocol processor 2615 OLT.

Here, for example, the LMC 2680 transmits a signal for controlling a custom LD (TLD) 2662 to a TLD 2662 and an electrical signal (hereinafter referred to as an electrical monitoring signal), which must be sent, being contained in the light to monitor the status of the optical link, to the FUC 2661, as illustrated in FIG. 27, so that light having different wavelengths is transmitted periodically.

FUC 2661 upconverts the received electrical signal into an RF carrier f _LM , which is sufficiently distant from the transmit / receive frequency band (hereinafter referred to as the modulation frequency band f _B ), as illustrated in FIG. 27, and then sends the upconverted frequency signal in TLD 2662.

The TLD 2662 modulates the upconverted signal at the appropriate wavelength according to the wavelength designation signal received by the LMC 2680, and transmits the resulting signal through the downlink WDM combiner 2640.

The optical monitoring signal that is input to the fiber optic line through the WDM combining unit 2640 passes through the fiber optic transmission line and RN 2630 and then is input to the ONU 2620. A portion of the optical power of the optical monitoring signal input to the ONU 2620 is input to the optical transmitting device 2622 and subjected to processing the amplification and reuse of the wavelength, and then again transmitted in the upstream direction.

The upstream optical monitoring signal is transmitted to the PD 2671 via an optical splitter 2650 and then converted to an electrical signal. The output of the PD 2671 is downconverted to the baseband in FDC 2671 and then transmitted to the LMC 2680.

The remainder of the optical monitoring signal transmitted to the ONU 2620 is transmitted to the optical receiving device 2623 (ONU). However, since a low-pass filter (LPF) is generally included in the TIA included in the receiver 2623, and the LPF only passes the baseband of the received signal through itself and removes the signal, such as an electrical monitoring signal, which is sufficiently distant from bandwidth, the electrical monitoring signal has no effect on the recovery of the downstream data stream.

Meanwhile, for example, a case where a break in an optical fiber occurs in a fiber optic transmission path can be detected when monitoring signals corresponding to all wavelengths are not received. In addition, for example, when optical fiber breakage occurs in a distribution network path, an optical monitoring signal corresponding to a cut optical fiber is not received.

Also, meanwhile, by using the highly sensitive PD 2671, light reflected on the surface cut off due to the breakage of the optical fiber can be detected, the optical transmitting device 2622 absorbs all the received light when the ONU 2620 is in the power off state, and thus the power off state ONU 2620 power supply and fiber breakage condition can be different from each other.

In addition, in the meantime, since the LMC 2680 has the function of an optical time domain reflectometer, the LMC 2680 can accurately detect the location at which the optical fiber breaks.

In addition, for example, in the case of the WDM-TDM-PON, since the RN 2630 includes a splitter 2633, the light wavelength is shared by a plurality of ONUs 2620. In this case, in general, the OLT 2610 has difficulty detecting a fiber break in the distribution path network.

However, in this case, according to the present invention, by using the uplink transmission time information distributed to the ONUs by the OLT MAC layer to transmit the light wavelength that the particular ONU receives in the time period assigned to the ONUs and receive the optical signal returned from the ONU at an appropriate time period, a fiber break in the distribution network path can be detected, and accordingly, a fiber break can be detected throughout the path from the OLT 2610 to a particular ONU 2620.

Meanwhile, part of the power of the optical monitoring signal passes through the WDM 2650 splitter and is transmitted to the optical receiver 2613 for receiving data. Since the transimpedance amplifier (TIA) installed in the receiver 2613 generally includes LPF, the receiver 2613 passes only the baseband of the received signal through itself and removes the signal, such as an electrical monitoring signal, that is sufficiently far from the baseband . Therefore, the electrical monitoring signal has no effect on upstream recovery.

FIG. 28 shows a detailed structure of the L-Tx 2660, L-Rx, and LMC 2680 included in the OLT 2610 according to another embodiment of the present invention, to determine optical fiber breakage between the OLT 2610 and the ONU 2620 or the operating mode of the ONU 2620 transmitter 2622.

The structure illustrated in FIG. 28 is similar to the structure illustrated in FIG. 27, except that the structure illustrated in FIG. 27 uses TLD 2662 as the L-Tx 2660, while the structure illustrated in FIG. 28, uses RSOA 2663, Optical Switch (OSW) 2664 1xn, and 2665 WDM Multiplexer as L-Tx 2660.

The source light is sent from the SL module 2600 to the WDM multiplexer 2665 through a circulator 2666. The WDM multiplexer 2665 divides the source light according to wavelengths and transfers each light to the optical switch 2664.

The optical switch 2664 transmits the specific light wavelength to the RSOA 2663 under the control of the LMC 2680. The RSOA 2663 amplifies and reflects the light and then modulates the resulting light by means of the current that is input from the FUC 2661.

A modulated light signal is introduced into the downlink fiber optic line through an optical switch 2664, a WDM multiplexer 2665, a 2666 circulator, and a WDM splitter 2640.

Another difference between the structure illustrated in FIG. 28 and the structure illustrated in FIG. 27 is that the wavelength of the light output from the transmitter 2612 is exactly equal to the wavelength of the light output from the L-Tx 2660 in the structure 28 illustrated in FIG. 28, and accordingly, the phenomenon of beats between the wavelengths of light can be handled simply by comparison with the structure illustrated in FIG. 27, in which the differences in the wavelength of the two optical sources are not uniform.

Fig. 29 shows a detailed structure of the L-Tx 2660, L-Rx 2670 and LMC 2680 included in the OLT 2610, according to another embodiment of the present invention, in order to determine a fiber break between the OLT 2610 and the ONU 2620 or the operating mode of the ONU 2620 transmitter 2622.

The structure illustrated in FIG. 29 is similar to the structure illustrated in FIG. 27, except that the structure illustrated in FIG. 29 uses TLD 2662 as the L-Tx 2660, while the structure illustrated in FIG. 29 uses the RSOA 2663 and the 2665 WDM Multiplexer as the L-Tx 2660.

The source light is input from the source light SL module 2600 to the WDM multiplexer 2665 through a circulator 2666. The WDM multiplexer 2665 divides the source light according to wavelengths and transmits each light to the RS63 matrix 2663.

The 2663 RSOA matrix amplifies and reflects the light and then modulates the resulting light using current introduced from the FUC 2661, under the control of the LMC 2680.

A modulated light signal is introduced into the downlink fiber optic line through a WDM multiplexer 2665, a 2666 circulator, and a WDM splitter 2640. As illustrated in FIG. 28, since the wavelength of the light outputted from the L-Tx 2612 is exactly equal to the wavelength of the light outputted from the L-Tx 2660, the structure illustrated in FIG. 28 allows the beat phenomenon to be processed between the light wavelengths simply by compared with the structure illustrated in FIG. 27, in which the difference between the wavelengths of the light of the two light sources is not uniform.

30-33 are views illustrating an output spectrum of a source light and a spectrum that has passed through a WDM demultiplexer when MWLS is used as an SL according to an embodiment of the present invention.

FIG. 30 shows a spectrum of light that is output from source light species 2601, a passband of a WDM multiplexer 2611 (see FIG. 29), and a spectrum that has passed through a WDM multiplexer 2611 when MWLS is used as a source light 2601.

The optical spectrum that is derived from each MWLS, as illustrated in FIGS. 30 and 31, includes a plurality of wavelengths. 30 and 31, each MWLS has the same wavelength Δ _WDM , but their central wavelength is arranged in an alternating format.

Accordingly, if two MWLSs are combined by means of a splitter, the light wavelengths of the two MWLSs have an alternating shape, and thus the wavelength range of the output spectrum is reduced to half its initial wavelength interval.

Accordingly, if an output light whose light wavelengths are more narrowly arranged passes through a WDM multiplexer 2611 having the bandwidth format illustrated in FIG. 32, the output light should have a spectrum illustrated in FIG. 33.

Each WDM MUX 2611 bandwidth for determining the communication channel includes three light wavelengths.

In fact, when several wavelengths exist in the same WDM channel, the downstream optical signal is distorted, and a power penalty can be formed due to the branching of the optical fiber if the transmission range is significant. Accordingly, the source light wavelength interval and the number of source light wavelengths that are included in the bandwidth of the WDM multiplexer should be considered appropriately according to the transmission distance.

FIGS. 34-36 illustrate three embodiments for implementing MWLS according to an embodiment of the present invention.

A structure such as DFB-LD, in which a single-mode laser (SML) array 3401 and a WDM 3410 multiplexer are combined separately as illustrated in FIG. 34, and a structure such as a Fabry-Perot cavity laser diode (FP- LD), in which a multimode laser array (MML) 3502 and a WDM 3401 multiplexer are combined separately with each other, are possible.

As illustrated in FIG. 35, a translucent mirror 3511 may be added to the output of the WDM multiplexer 3410 in order to improve the output light characteristic.

The structure illustrated in FIG. 36 includes an optical reflection module 3603, a WDM multiplexer 3410, an optical amplifier 3607, a circulator 3605, and a 1x2 splitter 3606.

In this embodiment, the mirror can be used as an optical reflective module 3603 and can adjust the difference in optical power between the output light wavelengths of the source light by varying the reflection coefficient or optical attenuation coefficient.

In addition, an active element, such as RSOA, can be used as an optical reflective module 3603. In this case, since the output light of each RSOA is modulated into an electrical signal, a plurality of modulated optical signals can be output from SL 2601.

The optical amplifier 3607 may be a fiber optic optical amplifier or a semiconductor optical amplifier.

The operation of the MWLS 2601 illustrated in FIG. 36 is described below. The light generated by the optical amplifier 3607 is injected into the circulator 3605 and the WDM MUX 3410. The light input to the WDM multiplexer 3401 is divided according to the wavelengths of the light and output to the optical reflective module 3603. The light is reflected by the light reflective module 3603 and then introduced back into multiplexer 3410 WDM.

The output optical signal from the WDM multiplexer 3410 is input to a 1x2 3606 optical splitter through a 3605 circulator. A portion of the optical power input to the 3606 optical splitter is output outside the MWLS 2601, and the remaining optical power is again fed to the 3607 optical amplifier.

Accordingly, “optical amplifier 3607 — circulator 3605 — multiplexer 3410 WDM — optical reflective module 3603 — multiplexer 3410 WDM — circulator 3605 — optical combiner 3606 — optical amplifier 3607” form a closed loop.

The light generated by the optical amplifier 3607 is converted to light having a laser generation characteristic or a characteristic similar to that of laser generation, while the light passes through a closed circuit and then is output outside the MWLS 2601.

Figs. 37-39 are views illustrating an output spectrum of a BLS, a bandwidth of a WDM multiplexing / demultiplexing unit (MUX / DeMUX), and an output spectrum that has passed through a WDM multiplexing / demultiplexing unit when a BLS is used as a source light according to an embodiment of the present inventions.

Fig. 37 illustrates the output spectrum of the BLS, Fig. 38 illustrates the bandwidth of the WDM multiplexer (MUX), and Fig. 39 illustrates the output spectrum for a particular channel that has passed through the WDM multiplexer.

Since the output bandwidth of the WDM multiplexer depends on the bandwidth of the WDM multiplexer, the transmission range and bandwidth of the WDM multiplexer must be determined taking into account the power penalty caused by the splitting of the optical fiber in the case of transmission over long-distance lines. BLS can be implemented in various forms.

For example, BLS can be implemented using a semiconductor superluminescent LED (SLD), a light source with amplified spontaneous emission (ASE) through an erbium doped fiber amplifier, a semiconductor optical amplifier, an ASE light source, etc.

FIG. 40 illustrates a WDM-PON structure in which uplink optical fiber is separated from downlink optical fiber in a transmission path between the OLT 2610 and RN 2630, according to an embodiment of the present invention.

The WDM-PON structure illustrated in FIG. 40 is the same as the structure illustrated in FIG. 26, except that the uplink transmission and downlink transmission, respectively, are performed through a different optical fiber in the transmission path between the OLT 2610 and RN 2630.

For this, a circulator 312 (2619 in FIG. 26) for separating the upward optical signal and the downward optical signal included in the OLT 2610 from each other is included in RN 2630. The remaining elements illustrated in FIG. 40 are the same as the corresponding the elements illustrated in FIG.

Since the structure illustrated in FIG. 40 performs upward and downward transmission through a separate optical fiber, the structure illustrated in FIG. 40 is relatively resistant to reflection of various optical signals that are generated in the transmission path. Accordingly, the structure illustrated in FIG. 40 has a less restriction on the transmission distance with respect to the reflection of the optical signal and, accordingly, is suitable for transmission over long-distance lines.

FIG. 41 illustrates a WDM-TDMA-PON structure using a source light to make the optical transmission of OLT independent of the light wavelength, according to an embodiment of the present invention.

Fig. 41 illustrates a WDM-TDM-PON structure using a light wavelength reuse method in which the source light is used to realize an OLT that is independent of the light wavelengths, the downstream optical signal is repeatedly used as rising light, and upstream data is transmitted to implement an ONU that is independent of the light wavelengths.

The transmission path between the OLT and the RN is connected via a single fiber link.

The WDM-TDMA-PON, which is independent of the light wavelength, includes an OLT 2610, a source light transmitting unit 2600, an RN 2630, and a plurality of ONU 2620.

The OLT 2610 has the same structure as the OLT illustrated in FIG. 26, except that the upstream light receiving unit can receive an optical packet in a burst mode since the upstream optical signal has a burst mode characteristic by using the TDMA method.

The structure of the source light transmitting unit 2600 is described above with reference to FIG.

The RN 2630 includes a WDM Multiplexing / Demultiplexing Module (MUX / DeMUX) 2631 and a 1xn optical power splitter 2633. The downstream signal 2630, which is input to the RN 2630, is divided according to the light wavelengths in the WDM multiplexing / demultiplexing unit 2631, and each wavelength is input to a 1xn optical power splitter 2633. The optical power of the wavelength is divided by 1 / n by a 1xn optical power splitter 2633, and the divided optical power is output to the plurality of ONUs 2620.

Upstream optical signals having the same wavelengths that are transmitted from the ONU 2610 are combined by an optical power splitter 2633 and then input to a WDM multiplex / demultiplexer (MUX / DeMUX) 2631. In the WDM multiplex / demultiplexer 2631, optical signals having different lengths light waves are multiplexed by wavelength and output to the OLT 2610.

The structure of each ONU 2620 is the same as the corresponding structure illustrated in FIG. 26, except that the upstream signal has a burst characteristic since ONUs transmitting at the same wavelength should transmit optical signals only in this particular time slot . Accordingly, the optical transmitter 2622 may have to transmit in burst mode.

Fig. 42 illustrates a WDM-TDMA-PON structure in which an optical fiber for upstream transmission is separated from an optical fiber for downstream transmission in a transmission path between an OLT 2610 and an RN 2630, according to an embodiment of the present invention.

The structure illustrated in FIG. 42 is the same as the structure illustrated in FIG. 41, except that the optical fiber for upstream transmission is separated from the optical fiber for downstream transmission in the transmission path between the OLT 2610 and RN 2630.

For this, a circulator 2632 (2619 in FIG. 26) for separating the upstream and downstream optical signals included in the OLT 2610 from each other is included in RN 2630.

The structure illustrated in FIG. 42 is relatively resistant to reflection of various optical signals that are generated in the transmission path, since the optical fiber for upstream transmission is separated from the optical fiber for downstream transmission.

FIGS. 43-45 illustrate structures of an RSOA-based input light wavelength reusable device according to an embodiment of the present invention.

Referring to FIG. 43, an RSOA-based input light wavelength reuse apparatus includes an optical splitter 4301, PD 4321, a transimpedance amplifier (TIA) 4322, a limit amplifier (LA) 4323, an inverter 4341, a first RF delay of 4342, circuit 4343 And, the first laser driver (LDD1) 4344, the second laser driver (LDD2) 4333, the module 4351 combining electrical signals, RSOA 4310 and the optical delay 4302.

The downstream optical signal that is received from the telephone exchange is divided by the optical splitter 4301 so that a portion of the downstream optical signal is input to the RSOA 4310, and the remaining portion of the downstream optical signal is input to the PD 4321. The downstream optical signal input to the PD 4321 is converted to the current signal is then output to the transimpedance amplifier 4322. The electrical signal is amplified by the transimpedance amplifier 4322, converted to a voltage signal, and then transmitted to the amplifier amplifier rer 4323. limiting amplifier 4323 re-amplifies the received voltage signal.

A part of the output signal of the amplifier-limiter 4323 is output to the processor 4324 of the downstream data signals, and the remaining part of the output signal is inverted by polarity by an inverter 4341 and then introduced into the first RF delay 4342. Here, if the amplifier-limiter 4323 has an output to invert the polarity of the signal and its output, the output signal is directly transmitted to the first RF delay 4342 without passing through the inverter 4341.

The output of the first RF delay 4342 is input to the 4343 I circuit.

Accordingly, part of the power of the downward signal is input to the input of the 4343 AND circuit, and part of the power of the downward signal is input to another input of the 4343 I.

Therefore, the downstream signal passes through the AND circuit 4343 when the upstream signal has a level of 1, and cannot pass through the And 4343 circuit when the upstream signal has a level of 0. The output of AND circuit 4343 is converted to a modulated signal by the first LDD 4344 and then output.

The remaining power of the uplink signal is input to the second LDD 4333 through the second RF delay 4332, converted to a modulated signal by the second LDD 4333, and then output with a bias current. The output of the first LDD 4344 and the output of the second LDD 4333 are combined by combining module 4351 and then input to RSOA 4313.

A portion of the downstream optical signal separated by the optical splitter 4301 is input to the front face 4311 of the RSOA 4310, reflected by the rear face 4312 of the RSOA 4310, and then transmitted again through the front face 4311.

In order to optimally reuse the light wavelength of the downstream optical signal that is input into the RSOA 4310, the phase of the previous injection current, which is ultimately output from the first LDD 4344, and the phase of the downstream optical signal that is input into the RSOA 4310 must be optimally matched. The matching of both phases is performed by the optical delay 4302 and the first RF delay 4342.

Meanwhile, since a portion of the upstream optical signal power is input to the combining unit 4351 via the And 4343 first circuit and the first LDD 4344, and the remaining upstream optical signal power is input to the combining unit 4351 through the second LDD 4333, the phases of the two signals are different from each other. The second RF delay 4332 serves to match the phases of the two signals.

The structure illustrated in FIG. 44 is the same as the structure illustrated in FIG. 43. In a method for directly modulating a downstream signal into an upstream data stream in RSOA, there are difficulties in modulating a signal into data that is larger than 2.5 Gbit / s due to the RSOA characteristic.

To modulate the signal into data that is larger than 2.5 Gbit / s, the RSOA output light is modulated by an external modulator (EM) 4305.

Therefore, a circulator 4304 for transmitting the output signal of the RSOA 4310 to the EM 4305 and a circulator 4303 for transmitting the output signal of the EM 4305 to the network are further included. The difference between the structure illustrated in FIG. 44 and the structure illustrated in FIG. 43 is that the output of the first LDD 4344 is input to the RSOA 4310, and the output of the second LDD 4333 is input to the EM 4305.

Therefore, RSOA 4310 performs reuse of the input light wavelength and amplification for the input optical signal using FFCI. Light modulation of the upstream data is performed by EM 4305.

The structure illustrated in FIG. 45 is the same as the structure illustrated in FIG. 43, except that the active region of RSOA 4310 is divided into two sections.

The upstream current signal, which is received from the second LDD 4333, is inputted together with the bias current into the front section 4313a of the two-section RSOA 4310, and the current signal for FFCI, which is received from the first LDD 4344, is input into the rear section 4313b of the two-section RSOA 4310.

Figures 46-49 illustrate the structure of an SOA-based input light wavelength reusable device according to an embodiment of the present invention.

The structure illustrated in FIG. 46 is basically the same as the structure illustrated in FIG. 43, except that SOA 4315 is used instead of RSOA 4310.

To circulate the SOA 4315 output signal to the network, a circulator 4303 is added. In contrast to FIG. 22, the downstream optical signal is input through the front section 4311 of the SOA 4315, aligned, optically amplified and modulated by the upstream signal, and then output to the rear section 4312 of the SOA 4315.

The structure illustrated in FIG. 47 is basically the same as that illustrated in FIG. 46, except that the output of the first LDD 4344 is input to the SOA 4315 and the output of the second LDD 4333 is input to the EM 4305. Accordingly, SOA 4315 performs alignment and amplification for the input optical signal using FFCI, and light modulation through the upstream data stream is performed using EM 4305.

The structure illustrated in FIG. 48 is basically similar to the structure illustrated in FIG. 46, except that the active region of SOA 4315 is divided into two sections.

The output signal of the first LDD 4344 is input to the front section 4313a SOA 4315, and the output of the second LDD 4334 is input to the rear section 4313b SOA 4315. In the front section 4313a SOA 4315, the input optical signal is aligned and amplified by FFCI, and in the rear section 4313b SOA 4315 light is modulated by upstream data.

The structure illustrated in FIG. 49 is basically similar to the structure illustrated in FIG. 46, except that the active region of SOA 4315 is divided into three sections.

The output of the first LDD 4344 is input to the front section 4313a of SOA 4315, and the output of the second LDD 4333 is input to the rear section 4313b of SOA 4315.

Accordingly, the front section 4313a of the SOA 4315 aligns the input optical signal with FFCI, the intermediate section 4313c of the SOA 4315 amplifies the optical signal, and the rear section 4313b of the SOA 4315 modulates the light by upstream data for the resulting optical signal.

Fig. 50 illustrates the structure of a simplified input light wavelength reusable apparatus using an LA terminal to reuse an optical signal received at the RSOA as transmission light according to an embodiment of the present invention.

Referring to FIG. 50, a simplified method for reusing the input light wavelength using the LA 4323 output signal to reuse the optical signal received at the RSOA as transmission light is described below.

A portion of the output of the limiter amplifier 4323 is inverted in polarity by an inverter 4341, passes through an RF delay 4342, and then amplified to an appropriate size by an RF amplifier (AMP) 4345.

In the meantime, the upstream signal is converted to a current signal by LDD 4333 and then output together with the bias current. The output of the RF amplifier 4345 and the output of the LDD 4333 are combined by combining module 4351 and input to the RSOA 4310.

If the LA 4323 includes a connector to invert the polarity of the signal, the output signal of the connector is used as is without passing through the 4341 inverter.

Fig. 51 illustrates the structure of a simplified input light wavelength reusable apparatus using a transimpedance amplifier (TIA) terminal in order to reuse an optical signal received at the RSOA as transmission light according to an embodiment of the present invention.

A portion of the output of the transimpedance amplifier 4322 is inverted in polarity by an inverter 4341, passes through an RF delay 4342, and amplified to an appropriate size by an RF amplifier 4345.

In the meantime, the upstream data signal is converted to a current signal in LDD 4333 and output together with the bias current. The RF output signal AMP 4345 and the output signal LDD 4333 are combined by combining module 4351 and then input to RSOA 4310.

If the TIA 4322 includes a connector to invert the polarity of the signal, the output signal of the connector is used as is without passing through the 4341 inverter.

Although the present invention is specifically shown and described with reference to its exemplary embodiments, those skilled in the art should understand that various changes in form and content can be made without departing from the spirit and scope of the present invention as defined by the appended claims inventions.

Claims (43)

1. Reflective semiconductor optical amplifier (RSOA) having one active region, while RSOA contains:
reflective face reflecting the input optical signal; and
an optical amplifying semiconductor located on the side of the reflective face to receive a combination of a first signal having a polarity opposite to that of the input optical signal and a second signal for modulating the input optical signal reflected from the reflective face to form an output optical signal. 2. Reflective semiconductor optical amplifier (RSOA) having two active areas, while RSOA contains:
reflective face reflecting the input optical signal; and
the rear region of the optical amplifying semiconductor, which is located on the side of the reflective face and into which a signal having a polarity opposite to the polarity of the input optical signal is input, and the front region of the optical amplifying semiconductor, which is located on the side of the front side through which the optical signal enters and through which pass the input optical signal and a signal for modulating the aligned optical signal reflected from the reflective face to form the output optical Signal. 3. A semiconductor optical amplifier (SOA) having three active regions, wherein the SOA contains:
a first active region receiving a signal having a polarity opposite to that of the input optical signal and equalizing amplitude of the input optical signal;
a second active region located on the side of the first active region to receive direct current and amplify the input optical signal that has passed through the first active region; and
a third active region located on the other side of the second active region to receive a signal for modulating a aligned optical input signal that has passed through the second active region to form an optical output signal. 4. The semiconductor optical amplifier according to claim 3, further comprising a spot size conversion region (SSC) that is added to the other side of each of the first active region and the third active region. 5. The control device reflective semiconductor optical amplifier (RSOA), while the device contains:
a splitter dividing the input optical signal into a first optical signal and a second optical signal;
An RSOA having one active region that reflects a second optical signal from a reflective face and into which a combination of a signal having a polarity opposite to that of the second optical signal and a signal for modulating a second optical signal reflected from the reflective face is introduced to form an output optical signal;
a photodiode converting the first signal into a current signal;
a transimpedance amplifier that amplifies and converts the current signal transmitted from the photodiode into a voltage signal;
a limit amplifier re-amplifying a voltage signal transmitted from a transimpedance amplifier;
the first RF delay circuit, which regulates the phase of the signal output from the limiter amplifier and the phase of the input optical signal in RSOA so that the intensity of the input optical signal input to RSOA is optimally aligned;
circuit And, passing the output signal of the first RF delay circuit through itself when the upstream signal has a level of "1", and not allowing the output signal of the first RF delay circuit through itself when the upstream signal has a level of "0";
a second RF delay circuit that optimally controls the phase of the upstream signal input to the AND circuit and the phase of the upstream signal transmitted through the second RF delay;
an optical delay line optically compensating for the electrical delay through the first RF delay circuit;
the first LD driver converts the output signal of the AND circuit into a current signal; and
a second LD driver that converts the output of the second RF delay circuit into a current signal. 6. The control device according to claim 5, further comprising:
An RF amplifier amplifying a voltage signal transmitted from a transimpedance amplifier and having a polarity opposite to that of the first optical signal to an equalization signal having a level suitable to equalize the optical amplitude of the second optical signal;
an RF delay circuit delaying the output time of the equalization signal transmitted from the RF amplifier so that the second optical signal is optimally aligned; and
a signal combining module combining an equalization signal transmitted from an RF delay module with a signal for modulating a second optical signal to generate an output optical signal, and inputting the combined signal into one active RSOA region. 7. The control device according to claim 6, further comprising an amplifier-limiter, re-amplifying the voltage signal transmitted from the transimpedance amplifier, and transmitting the re-amplified voltage signal having a polarity opposite to that of the first optical signal to the RF amplifier. 8. The control device according to claim 5, in which RSOA is an optical amplifier having two active regions, and which contains a reflective face that reflects the input optical signal; and a rear region of the optical amplifying semiconductor, which is located on the side of the reflective face and into which a signal having a polarity opposite to the polarity of the input optical signal is input, and a front region, which is located on the other side of the rear region and through which the input optical signal and the modulation signal pass an input optical signal reflected from the reflective face to form an output optical signal,
in which the equalization signal transmitted from the first LD driver is input into the back region of the RSOA having two active regions, and
in which a signal for modulating a second optical signal to generate an optical output signal is input to a front region of an RSOA having two active regions. 9. A downlink optical transmission device using wavelength independent optical transmitting devices that is used in an optical line terminal (OLT) of a passive optical network with wavelength division multiplexing (WDM-PON), comprising:
a source light module generating a multiwave optical signal; moreover, the source light module generates optical signals multiplexed by wavelength, and includes an erbium-doped fiber or semiconductor amplifier;
a wavelength multiplexing / demultiplexing module dividing a multiwave optical signal according to wavelengths;
optical transmitting devices generating downward optical signals using optical signals received from a source light module through a wavelength multiplexing / demultiplexing module in response to a plurality of electrical signals received from an external device; and
a circulator transmitting the multi-wavelength optical signal to the wavelength multiplexing / demultiplexing module and transmitting optical signals from the optical transmitting devices through the wavelength multiplexing / demultiplexing module towards the subscribers,
wherein the wavelength multiplexing / demultiplexing unit multiplexes downlink optical signals generated by optical transmitting devices with wavelength division multiplexing. 10. The device according to claim 9, in which the passband of the BW _{MWS of} the source light module satisfies Equation 1, and the relationship between the bandwidth of the WDM channel Δλ _{passband of the wavelength division} multiplexing / demultiplexing module and the interval of the output wavelength Δλ _{MWS of} the source light module satisfies equation 2:

where N is the number of available WDM-PON channels, and Δλ _WDM is the WDM-PON channel slot. 11. The device according to claim 10, in which the bandwidth of the WDM channel Δλ _passband satisfies equation 3, when the module multiplexing / demultiplexing by wavelength has a wavelength interval of 200 GHz:

12. The device according to claim 9, in which the optical transmitting devices are wavelength-independent semiconductor amplifiers. 13. A downlink optical transmission device using wavelength independent optical transmitters that is used in a passive optical network with wavelength division multiplexing (WDM-PON), comprising:
a source light module generating wideband optical signals multiplexed by wavelength; moreover, the source light module generates broadband optical signals multiplexed by wavelength, and includes a semiconductor superluminescent LED (SLD), erbium doped fiber amplifier or semiconductor optical amplifier;
a wavelength multiplexing / demultiplexing module dividing a broadband optical signal multiplexed by a wavelength according to wavelengths;
an optical transmission module generating downward optical signals using optical signals received from a wavelength multiplexing / demultiplexing module in response to a plurality of electrical signals received from an external device; and
a circulator transmitting a broadband optical signal to a wavelength multiplexing / demultiplexing module and transmitting optical signals from optical transmitting devices through a wavelength multiplexing / demultiplexing module to subscribers,
in which the wavelength multiplexing / demultiplexing unit multiplexes along the wavelength with a plurality of downlink optical signals generated by optical transmitting devices. 14. The device according to item 13, in which the full passband BW _BLS module of the source light satisfies equation 4:

where N is the number of available WDM-PON channels, and Δλ _WDM is the WDM-PON channel slot. 15. The device according to 14, in which the module multiplexing / demultiplexing by wavelength determines the bandwidth of the WDM channel Δλ _passband that satisfies equation 5, when the wavelength interval is 200 GHz:

16. The device according to item 13, in which the optical transmitting devices are wavelength-independent semiconductor optical amplifiers. 17. A downlink optical transmission method using wavelength independent optical transmitters that are included in an optical line terminal (OLT) of a passive optical network with wavelength division multiplexing (WDM-PON), comprising the steps of:
forming a multi-wavelength optical signal using a multi-wavelength light source;
divide the multi-wavelength optical signal according to wavelengths;
generating a plurality of downstream optical signals with each optical signal received and shared according to wavelengths, in response to a plurality of electrical signals received from an external device; moreover, the formation of a plurality of downward optical signals comprises the step of generating a plurality of downward optical signals using a plurality of semiconductor optical amplifiers independent of the wavelength; and
a plurality of downstream optical signals are multiplexed by wavelength separation and transmit WDM signals to the subscriber side via an optical line. 18. A downlink optical transmission method using wavelength-independent optical transmitters that are included in an optical line terminal (OLT) of a passive optical network with wavelength division multiplexing (WDM-PON), comprising the steps of:
generating broadband optical signals multiplexed by wavelength using a broadband light source (BLS);
dividing a broadband optical signal multiplexed by wavelength according to wavelengths;
generating a plurality of downstream optical signals with each optical signal received and shared according to wavelengths, in response to a plurality of electrical signals received from an external device; moreover, the formation of a plurality of downward optical signals comprises the step of generating a plurality of downward optical signals using a plurality of semiconductor optical amplifiers independent of the wavelength; and
multiple downlink optical signals are multiplexed by wavelength and transmit the result of the WDM signals to the subscriber side via an optical line. 19. An optical line terminal (OLT), including wavelength independent optical transmitters, which is used in a passive optical network with wavelength division multiplexing (WDM-PON), comprising:
a protocol processor performing protocol processing of the downstream electrical signal to be transmitted to the subscriber side or the upstream electrical signal transmitted from the subscriber side;
a downlink optical transmission module generating a plurality of downlink optical signals in response to each downstream electrical signal output from the protocol processor using multi-wavelength optical signals or broadband optical signals multiplexed by a wavelength and a plurality of downlink optical signals multiplexed by a wavelength, wherein the downlink module optical transmission includes a semiconductor superluminescent LED (SLD), erbium-doped fiber amplifier l or a semiconductor optical amplifier;
a circulator transmitting downstream optical WDM signals to the subscriber side via an optical line; and
an uplink optical reception module that receives upstream WDM optical signals transmitted from the subscriber side through an optical line through a circulator dividing the upstream optical WDM signal according to wavelengths, converting each optical signal into an electrical signal and outputting the electrical signal to a protocol processor. 20. OLT according to claim 19, in which the module downward optical transmission is a module downward optical transmission according to one of claims 9-16. 21. A passive optical network system with wavelength division multiplexing (WDM-PON), comprising:
the source light module forming the source light, the wavelength interval of which and the central wavelengths are controlled using at least two source light sources, the source light module comprising:
at least one source of the source light forming the source light having predetermined wavelengths;
an optical splitter combining and redistributing the source light generated by at least one source of source light;
an optical amplifier amplifying the optical signal output from the optical splitter; and
an optical power splitter splitting the amplified optical signal and transmitting the broken optical signal to the OLT;
an optical line terminal (OLT) receiving source light from a source light unit, transmitting downlink optical signals to WDM-PON subscribers, and receiving uplink optical signals transmitted from subscribers;
an optical network module (ONU) transmitting an uplink optical signal and receiving a downlink optical signal transmitted from an OLT, which is repeatedly used as light to transmit an uplink optical signal. 22. The system of claim 21, further comprising a wavelength multiplexing / demultiplexing module dividing the downlink optical signal transmitted from the OLT according to wavelengths and multiplying the wavelength uplink optical signal transmitted from the ONU. 23. The system of claim 22, wherein the OLT and the wavelength division multiplexing / demultiplexing unit are connected through one optical fiber to each other. 24. The system of claim 20, wherein the OLT comprises:
an OLT protocol processor performing protocol processing for a downstream data stream to be transmitted to a subscriber side and an upstream data stream transmitted from a subscriber side,
descending optical transmitting devices, each of which transmits a descending optical signal, transfers a downward data stream generated by modulating the source light introduced into the transmitting device to the subscriber side; and
upstream optical receivers, each of which receives an upstream optical signal carrying an upstream data stream that the subscriber side wants to transmit. 25. The system according to paragraph 24, in which part of the downward optical transmitting device contains:
optical downlink modulators, each of which modulates the source light so that the source light carries a downward data stream;
a downstream wavelength division multiplexer that multiplexes downlink optical signals transmitted from downlink optical signal modulators along a wavelength;
a circulator separating the source light signal from the downstream optical signals transmitted from the downstream optical signal multiplexer; and
a downlink optical signal amplifier amplifying the downlink optical signal transmitted from the circulator so that the downlink optical signals are transmitted to the ONU. 26. The system according to paragraph 24, in which part of the upstream optical receiving device contains:
an uplink optical signal amplifier amplifying uplink optical signals to compensate for transmission loss of the uplink optical signals;
an uplink optical signal demultiplexer dividing the upstream optical signals transmitted from the uplink optical signal amplifier according to wavelengths; and
demodulators of upstream optical signals, each of which demodulates the upstream optical signal to extract an upstream data stream included in the upstream optical signal transmitted from the demultiplexer of the upstream optical signals. 27. The system of claim 24, further comprising:
a control optical signal transmitter transmitting an optical control signal;
a control optical signal receiving device receiving a control optical signal after the control optical signal passes through a passive optical network;
a communication line monitoring controller controlling the transmission of optical signals of the control optical signal transmitter and the reception of optical signals of the control optical signal receiving device and determining whether the optical fiber connecting the OLT to the ONU is cut off and whether the optical transmission is of good quality based on the control optical signal;
a first splitter transmitting the control optical signal to the optical fiber so that the control optical signal is transmitted in a downward direction; and
a second splitter separating the pilot optical signal after the pilot optical signal passes through the passive optical network from the optical fiber to receive the pilot optical signal from the optical fiber. 28. The system according to item 27, in which the transmitting device control optical signals contains:
a first frequency converter receiving a control electric signal from a communication line monitoring controller and converting a frequency of a control electric signal using an RF carrier allocated in a frequency domain that is sufficiently far from the baseband; and
a control light source module, modulating the control optical signal with a control electric signal whose frequency is converted, and generating a modulated optical signal. 29. The system of claim 28, wherein the control light source module comprises:
an optical switch module receiving an initial light and outputting an optical signal having a predetermined wavelength; and
a reflective semiconductor optical amplifier (RSOA), which modulates the optical signal received from the optical switch module using the control electric signal received from the first frequency converter and the control electric signal received from the communication line monitoring controller. 30. The system of claim 28, wherein the control light source module comprises:
an optical signal multiplexing / demultiplexing module, receiving the source light, dividing the source light according to wavelengths and outputting the optical signal; and
a reflective semiconductor optical amplifier (RSOA) matrix module that modulates the optical signal received from the optical signal multiplexing / demultiplexing module using the control electric signal received from the first frequency converter and the control electric signal received from the communication line monitoring controller. 31. The system according to item 27, in which the receiving device control optical signals contains:
an optical signal converter that receives a pilot optical signal after the pilot optical signal passes through the PON and converts the pilot optical signal into an electrical signal; and
a second frequency converter that converts the frequency of the electrical signal received from the optical signal converter into a modulating frequency band. 32. The system according to item 21, in which the source of the source light contains:
an optical amplifier forming an optical signal;
an optical reflection module reflecting an optical signal by varying a reflection coefficient and an optical attenuation coefficient of an optical signal;
an optical signal multiplexing / demultiplexing module, receiving an optical signal generated by an optical amplifier, dividing the optical signal according to wavelengths, and transmitting the divided optical signal to the optical reflective module;
an optical splitter receiving an optical signal reflected by the optical reflective module, transmitting part of the optical signal power to the outside and transmitting the remaining part of the optical signal power to the optical amplifier; and
a circulator transmitting the optical signal generated by the optical amplifier to the optical signal multiplexing / demultiplexing module and transmitting the optical signal reflected by the optical reflective module to the optical splitter. 33. The system of claim 22, wherein the OLT and the wavelength multiplexing / demultiplexing unit at the remote site are connected to each other so that the uplink transmission and downlink transmission are respectively performed through separate optical fibers. 34. The system according to item 21, in which the ONU contains:
an ONU protocol processor performing protocol processing for the downstream data stream to be transmitted to the subscriber side and the upstream data stream transmitted from the subscriber side,
an upstream optical transmitter that aligns and optically amplifies the downstream optical signal so as to convert the downstream optical signal into upstream light, modulating the upstream light into an upstream optical signal transferring the upstream data stream that the subscriber side wants to transmit, and then transmitting the upstream optical signal;
a downstream optical receiver receiving a downlink optical signal carrying a downstream data stream and extracting a downstream data stream; and
an optical splitter dividing the power of the downstream optical signal and transmitting the divided powers of the downstream optical signal to the upstream optical transmitter and the downlink optical receiver. 35. The system according to paragraph 24, in which the optical transmitting device comprises:
an optical splitter dividing the power of the downstream optical signal into a first optical signal and a second optical signal and outputting a first optical signal and a second optical signal;
a photodiode converting the first optical signal into a current signal;
a transimpedance amplifier that amplifies the current signal transmitted from the photodiode and converts the amplified current signal into a voltage signal;
a limit amplifier re-amplifying a voltage signal transmitted from a transimpedance amplifier;
the first delay module, which regulates the phase of the output of the voltage signal, the polarity of which is inverted relative to the second optical signal, from the amplifier-limiter so that the second optical signal is optimally aligned;
a circuit And transmitting the output signal of the first delay module through itself when the upstream data stream has a level of "1", and not allowing the output signal of the first delay module through itself when the upstream data stream has a level of "0";
a second delay module that controls the phase of the output signal output from the AND circuit and the phase of the output signal from the second delay module so that the phase of the output signal from the AND circuit is equal to the phase of the output signal from the second delay module;
the first LD driver converts the output signal of the AND circuit into a current signal;
a second LD driver converting the output of the second RF delay circuit into a current signal; and
a reflective semiconductor optical amplifier (RSOA) equalizing the second optical signal with a current signal output from the first LD driver, and modulating the second optical signal into an upward optical signal to generate an upward optical signal when the second optical signal is reflected from the reflective face, s using the current signal output from the second LD driver. 36. The system of claim 35, further comprising:
a first circulator transmitting a second optical signal to the RSOA, receiving the aligned signal from the RSOA, and transmitting the aligned optical signal to the outside,
an external modulator receiving the aligned optical signal from the first circulator and modulating the aligned optical signal to generate an upward optical signal using a signal output from the second LD driver; and
a second circulator transmitting the upward optical signal from the external modulator to the wavelength multiplexing / demultiplexing unit at the remote node and transmitting the downstream optical signal to the optical splitter,
wherein RSOA aligns the second optical signal with a signal output from the first LD driver. 37. The system of claim 35, wherein the RSOA comprises two active regions having a rear region for aligning the second optical signal with a signal received from the first LD driver, and a front region for transmitting the second optical signal through the rear region and reflecting the second optical the signal from the reflection face and modulating the reflected second optical signal to form an upward optical signal using a signal received from the second LD driver. 38. The system according to clause 35, in which the optical transmitting device contains:
an optical splitter dividing the power of the downstream optical signal into a first optical signal and a second optical signal and outputting a first optical signal and a second optical signal;
a photodiode converting the first optical signal into a current signal;
a transimpedance amplifier that amplifies the current signal transmitted from the optical diode and converts the amplified current signal into a voltage signal;
a limiter amplifier reinforcing a voltage signal transmitted from a transimpedance amplifier;
the first delay module that controls the phase of the output of the voltage signal, the polarity of which is inverted relative to the second optical signal, from the amplifier-limiter so that the second optical signal is optimally aligned;
a circuit And transmitting the output signal of the first delay module through itself when the upstream data stream has a level of "1", and not allowing the output signal of the first delay module through itself when the upstream data stream has a level of "0";
a second delay module that controls the phase of the signal output from the And circuit and the phase of the output signal output from the second delay module so that the phase of the signal output from the And circuitry is equal to the phase of the output signal from the second delay module;
the first LD driver converts the output signal of the AND circuit into a current signal;
a second LD driver converting the output of the second RF delay circuit into a current signal;
a semiconductor optical amplifier (SOA) equalizing the second optical signal with a combined signal from a signal output from the first LD driver and a signal output from the second LD driver and modulating the aligned signal to form an upward optical signal; and
a circulator transmitting an upward optical signal to a wavelength multiplexing / demultiplexing unit at a remote site. 39. The system of claim 38, further comprising an external modulator receiving a second optical signal aligned by SOA and modulating a second optical signal to generate an upward optical signal using a signal output from the second LD driver,
wherein the SOA aligns the second optical signal with a signal output from the first LD driver. 40. The system of claim 38, wherein the SOA comprises two active regions having a front region for aligning a second optical signal with an output signal from a first LD driver and a rear region for modulating a second optical signal aligned by a front region to form an upward optical signal using a signal output from the second LD driver. 41. The system of claim 38, wherein the SOA comprises three active regions having a front region for aligning a second optical signal with a signal output from a first LD driver, an intermediate region for optical amplification of a second optical signal aligned with a front region, and a back region for modulating a second optical signal optically amplified by the intermediate region to form an upward optical signal. 42. The system of claim 34, wherein the optical transmitting device comprises:
an optical splitter dividing the power of the downstream optical signal into a first optical signal and a second optical signal and outputting a first optical signal and a second optical signal;
a photodiode converting the first optical signal into a current signal;
a transimpedance amplifier that amplifies the current signal transmitted from the optical diode and converts the amplified current signal into a voltage signal;
a limit amplifier re-amplifying a voltage signal transmitted by a transimpedance amplifier;
a delay module that controls the phase of the output of the voltage signal, the polarity of which is inverted relative to the second optical signal, from the amplifier-limiter so that the second optical signal is optimally aligned;
An RF amplifier that regulates the signal transmitted from the delay module so that the amplitude of the second optical signal is optimally aligned;
LD driver that converts the upstream data signal into a current signal;
RSOA equalizing the second optical signal with a signal output from the RF amplifier, and modulating the aligned second optical signal to generate an upward optical signal with a signal output from the LD driver when the second optical signal is reflected from the reflective face. 43. The system of claim 42, wherein the delay module adjusts the phase of the voltage signal output from the transimpedance amplifier without passing through the limit amplifier so that the second optical signal is optimally aligned.

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