KR20010003638A - Apparatus and method for stabilizing output power of wavelength division multiplexed erbium doped fiber amplifier in respect of channel number - Google Patents

Abstract

The present invention relates to output stabilization of an optical fiber amplifier provided in an optical repeater in a wavelength division multiplexing optical transmission system. Particularly, in order to stabilize output according to a change in the number of channels, the optical signal is partially diverted, and the split optical signal is divided into respective data. By analyzing the wavelength division demultiplexing by the wavelength band set for each channel, the number of channels currently used for transmission is analyzed, and the intensity of the output optical signal is controlled according to the number of the identified channels. Stabilization reduces the time required for stabilization of output and improves transmission quality.

Description

Output stabilization apparatus and method corresponding to the number of channels of a wavelength-division multiplexed optical fiber amplifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the stabilization of an output of an optical fiber amplifier provided in an optical repeater in a wavelength-division multiplex (WDM) optical transmission system, and more particularly, an apparatus for stabilizing its output power according to the number of channels of an input optical signal. It is about a method.

The optical fiber amplifier used in the optical transmission system is an apparatus for amplifying a transmitted optical signal. Since the optical signal itself is amplified without photoelectric conversion, the configuration is simple and economical.

Optical amplification by optical fiber is stimulated emission of active optical fiber added with rare earth element erbium (Er [68]), Pr (praseodymium [59]) or Yb (ytterbium [70]). It is done through the process.

In the wavelength division multiplexing method widely adopted in the optical transmission system, the 1550 nm wavelength band (about 1530 nm to 1560 nm) is mainly used as a signal band, and therefore, due to its characteristics, erbium is suitable for amplifying an optical signal in the 1550 nm band. Fiber Doped Fiber Amplifier (hereinafter referred to as EDFA) is mainly used. The EDFA mainly amplifies an optical signal transmitted by being provided in an optical repeater or the like.

FIG. 1 is a schematic block diagram of an output stabilization related part of an optical fiber amplifier (EDFA) and a number of channels in one optical repeater of a conventional wavelength division multiple optical transmission system. Referring to FIG. 1, an optical signal input to a repeater through an input terminal 11 first passes through a wavelength selective coupler (WSC) 13 of a data channel and a supervisory channel (SVC). It is separated into an optical signal. In general, the data channel is used for transmitting user data, and the management channel is used for transmitting various operational information of the system itself.

The optical signal of the data channel separated from the input terminal WSC 13 is then amplified by the EDFA 9 and provided to the output terminal WSC 14, and the optical signal of the management channel is transmitted by the optical receiver (RX) 15. Is converted to the system control unit 10 of the optical repeater. The system controller 10 provides control signals and the like to various functional units (not shown) including the EDFA 9 according to the information of the management channel and collectively controls the overall operation of the optical repeater. In addition, the system control unit 10 outputs the information of the management channel to the optical transmission unit (TX) (16). The output information of the management channel is converted into an optical signal by the optical transmission unit 16 and then combined with the optical signal of the data channel amplified by the EDFA 9 and output terminal ESC 14 and output to the output terminal 12.

On the other hand, EDFA (9) shown as an example in FIG. 1 is a bidirectional pumping structure, a first laser diode (LD: Laser Diode) (22a) for providing pump light to the EDF (Erbium Doped Amplifier) 29 in the forward and reverse directions, respectively ) And the second LD 22b. The pump light output from the first LD22a and the second LD22b is combined with an optical signal by the first WSC 21a and the second WSC 21b, and provided to the EDF 29, respectively.

The optical signal of the data channel separated from the input terminal WSC 13 and input to the EDFA 9 passes through an input optical splitter 23, an input optical isolator 27, and a first WSC 21a (Erbium Doped Amplifier) (EDF). Is provided and amplified. The amplified optical signal is then output through the second WSC 21b, the output stage optical isolator 28, and the output stage optical splitter 24. The input end optical splitter 23 and the output end optical splitter 24 are for detecting the intensity of each of the optical signal inputted to the EDFA 9 and the output optical signal, and a predetermined amount of each of the input optical signal and the output optical signal, For example, 1/100 is branched and output to the input photo-diode (PD) 25 and the output PD (26), respectively.

The input and output optical signals provided to the input terminal PD 25 and the output terminal PD 26 are converted into electrical signals and provided to the electronic control unit 20. The electronic control unit 20 controls the input optical signal and the output optical signal through them. Figure out. The electronic controller 20 detects the intensity of the input / output optical signal and controls the output of the first LD 22a and the second LD 22b so that the intensity of the output optical signal is stabilized at an appropriate level.

As described above, the output stabilization operation of the EDFA 9 is performed such that the intensity of the output optical signal is stabilized at a predetermined target value, wherein the target value is set differently according to the number of channels. That is, the output stabilization operation of the EDFA 9 is performed such that the light intensity is stabilized at a predetermined level for each channel. Therefore, as the number of channels increases, the target value of the output optical signal intensity increases. For example, when transmitting in 16 channels, the target value of the intensity of the output optical signal is twice as high as when transmitting in 8 channels. Thus, the intensity of output light for each channel is the same in 16 or 8 channels. You will be able to maintain your level.

In the WDM transmission method, the number of channels is frequently changed due to network reconfiguration, defects, or add / drop of channels. The information on the number of channels is obtained by the system control unit 10 through the management channel and provided to the electronic control unit 20 of the EDFA 9. Accordingly, the electronic control unit 20 of the EDFA 9 sets the target value of the output optical signal strength to match the current number of transmission channels.

As described above, the technology for stabilizing the output of EDFA corresponding to the number of channels is disclosed in Korean Patent Application No. 98-9032 (name: wavelength division multiplexing optical fiber amplifier with constant output power in optical relay system) For example).

However, when the number of data channels transmitted is changed, the electronic control unit 20 of the EDFA 9 may not immediately respond to the changed number of channels. That is, the information about the number of data channels is included in the information of the management channel, which is captured by the system controller 10 via the input terminal WSC 15 and the optical transmitter 15, and then the electronics of the EDFA 9. This is because it is provided to the control unit 20. For example, when a WDM system transmitting 16 channels converts the data into 8 channels and transmits the data, the EDFA 9 controls the intensity of the output optical signal to a target value corresponding to 16 channels and then uses the 8 channel optical signal. Since the intensity of the input optical signal decreases instantaneously, the amplification rate of the optical signal is increased to maintain the intensity of the output optical signal. As a result, the intensity of each channel of the output optical signal is suddenly increased.

Since the electronic control unit 20 of the EDFA 9 does not immediately respond to the change in the number of channels as described above, the time required for stabilization of the output becomes long, and such an overshoot or the like occurs when the optical signal is transmitted. Undershoot will occur.

Accordingly, an object of the present invention is to provide an apparatus and method capable of stabilizing an output in response to a change in the number of channels in a wavelength division multiplex optical amplifier.

Another object of the present invention is to provide an apparatus and method for stabilizing an output according to a channel number change of a wavelength division multiplexing optical amplifier which can reduce the time required for stabilizing an output.

Still another object of the present invention is to provide an apparatus and method for stabilizing an output according to a change in the number of channels of a wavelength division multiplexing optical amplifier that can improve transmission quality.

In order to achieve the above object, the method of the present invention provides a method for stabilizing an output according to a change in the number of channels of a wavelength division multiplexed optical fiber amplifier. A process of outputting by multiplexing the wavelength division demultiplexing for each channel, analyzing the light demultiplexed by the wavelength band, and determining the number of channels currently used for transmission, and controlling the intensity of the output optical signal according to the determined number of channels. It is characterized by having a process.

In order to achieve the above object, the device of the present invention is an output stabilization device according to a change in the number of channels of a wavelength-division multiplexed optical fiber amplifier, wherein the predetermined amount of light is installed at a predetermined position on an optical signal path of the optical fiber amplifier and passes. An optical diverter for dividing the signal, a demultiplexer for splitting and splitting the light splitted by the optical splitter into wavelength bands set for each data channel, and a demultiplexed and output light for each wavelength band, respectively. A photoelectric conversion unit for converting the signal, a comparison unit for comparing the level of each electrical signal converted in the photoelectric conversion unit with a preset reference level, and outputting a result value thereof; and storing the result value output from the comparison unit. And an optical island for identifying the number of channels through the information stored in the storage unit and performing an amplification control operation corresponding thereto. It characterized by having an electronic control unit of the amplifier.

1 is a schematic block diagram of an output stabilization related part of an optical fiber amplifier corresponding to the number of optical amplifiers and channels in one optical repeater of a conventional wavelength division multiple optical transmission system;

2 is a schematic block diagram of an output stabilization related part of an optical fiber amplifier corresponding to the number of channels and an optical fiber amplifier in one optical repeater of a wavelength division multiplexing optical transmission system according to an embodiment of the present invention;

3 is a block diagram illustrating a channel number detector of FIG. 2.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific details such as specific components are shown, which are provided to help a more general understanding of the present invention, and it is understood that these specific details may be changed or changed within the scope of the present invention. It is self-evident to those of ordinary knowledge in Esau.

2 is a schematic block diagram of an output stabilization related part of an optical fiber amplifier corresponding to the number of channels and an optical fiber amplifier in one optical repeater of a wavelength division multiplex optical transmission system according to an exemplary embodiment of the present invention. Referring to FIG. 2, the EDFA 9 according to the present invention does not receive information on the number of channels from the system controller 10 in order to stabilize the output optical signal corresponding to the number of channels unlike the conventional art.

In the present invention, the channel number detection unit 30 for detecting the information on the number of channels is installed in the EDFA (9), the channel number detection unit 30 detects the number of channels and provides it to the electronic control unit (20). Unlike the related art, the present invention does not grasp information about the number of channels by analyzing an optical signal of a management channel (SVC: SuperVisory Channel). Thus, the configuration of separation of the management channel is not shown in FIG. 2. However, the present invention may have a configuration in which the channel number detection unit 30 is added to a system for analyzing information of a conventional management channel as shown in FIG. 1. The reason for configuring such a separate channel number detection unit 30 is to detect the number of channels in the EDFA 9 itself to reduce the time required to determine the number of conventional channels and to stabilize the output in response to the change in the number of channels immediately. .

In particular, in the conventional method in which the electronic control unit 20 in the EDFA 9 knows the number of channels by the information provided from the system control unit 10, when the system control unit 10 has a large operating load, the electronic control unit ( 20) it may take longer to know the information about the number of channels. In contrast, in the present invention, since the number of channels is detected in the EDFA 9 itself, the electronic controller 20 immediately knows the number of channels regardless of the load on the system controller 10. Hereinafter, a detailed configuration of the EDFA 9 according to the present invention will be described.

EDFA 9 according to an embodiment of the present invention is a bidirectional pumping structure as in the prior art, the EDF 29, the first LD (22a), the second LD (22b), the first WSC (21a), the second WSC (21b) , An input stage optical splitter 23, an input stage PD 25, an input stage optical isolator 27, an output stage optical isolator 28, an output stage optical splitter 24, and an output stage PD 26. Same as before.

That is, the optical signal of the data channel input to the EDFA 9 through the input terminal 11 is provided to the EDF 29 via the input optical splitter 23, the input optical isolator 27 and the first WSC 21a. Is amplified. The amplified optical signal is then output through the second WSC 21b, the output stage optical isolator 28, and the output stage optical splitter 24. Light split by a predetermined amount from the input optical signal and the output optical signal by the input optical splitter 23 and the output optical splitter 24 is converted into an electrical signal by the input terminal PD 25 and the output terminal PD 26. It is provided to the electronic control unit 20. The electronic controller 20 determines the intensity of the input optical signal and the output optical signal through this and controls the output of the first LD 22a and the second LD 22b to adjust the intensity of the output optical signal.

The amplified optical signal output from the EDFA 9 through the output stage optical splitter 24 is an optical splitter 31 provided to branch some light used for detecting the number of channels according to the feature of the present invention. Going through. The optical splitter 31 branches off a predetermined amount, for example, 1/100, from the light passing through. The light branched from the optical splitter 31 is provided to the channel number detector 30.

The channel number detector 30 analyzes the light output for each data channel by wavelength division demultiplexing the provided light to find the number of channels currently used for transmission. Information about the number of channels determined by the channel number detector 30 is provided to the electronic controller 20, and accordingly, the electronic controller 20 controls the intensity of the output optical signal according to the number of channels of the optical signal currently transmitted. Done.

3 is a block diagram of the channel number detector 30 of FIG. 2. Referring to FIG. 3, the channel number detector 30 receives a light branched from the output light by the optical splitter 31, and demultiplexes and outputs the wavelength division demultiplexed by the wavelength band set for each data channel (AWG). (32). In FIG. 3, the demultiplexer 32 may be configured using an arrayed-waveguide grating (AWG). In addition, the demultiplexer 32 may be configured using a plurality of fiber grating filters. In general, it is economical to use a plurality of optical fiber grating filters than AWG when the number of channels to be divided is small, and to use one AWG when the number of channels to be divided is large. In order to analyze the optical signal and determine the number of channels of the currently transmitted optical signal, all wavelength bands of all channels used in the WDM system must be identified. Therefore, in the present invention, the demultiplexer 32 is preferably configured as an AWG. .

The light output for each wavelength band from the demultiplexer 32 is provided to the photoelectric converter 34 and converted into electrical signals, respectively. The photoelectric converter 34 may be configured as an array of a plurality of photodiodes provided for each wavelength band in order to receive light output for each wavelength band and convert the light into electrical signals.

Each electrical signal converted at the photoelectric converter 34 is provided to a comparator 36 so that each level is compared with a preset reference level. The comparator 36 receives the electrical signal as one input terminal, receives an input signal of a predetermined reference level as the other input terminal, and compares it, and installs an operational amplifier (OP AMP) for each electrical signal. Can be configured as In this case, the reference level is appropriately set to a level capable of determining the presence or absence of a signal in the photoelectrically converted electrical signal for each wavelength band. In addition, the comparison result is output as "1" or "0".

The result value output from the comparator 36 is stored in the register 38. In this case, the register 38 is configured as a shift register to count the comparison result value output as "1". Information stored in the register 38 is provided to the electronic control unit 20, the electronic control unit 20 to determine the number of channels through this.

Referring to the operation of the channel number detection unit 30 having the above configuration, the optical signal provided by the optical splitter 31 is demultiplexed by the wavelength band of each data channel in the demultiplexer 32 to the photoelectric converter 34. Is provided. Thereafter, each electrical signal converted for each of the wavelength bands in the photoelectric converter 34 is provided to the comparator 36 to determine the presence or absence of the signal according to each level.

That is, when the level of each electrical signal converted for each wavelength band is equal to or greater than the reference level set in the comparator 36, the signal is considered to be present, and when the level of the electrical signal is equal to or less than the reference level, it is regarded as no signal. . By determining the presence or absence of such a signal, it is possible to determine whether the corresponding wavelength band is currently in use.

The result value output from the comparator 36 for the presence or absence of the signal is " 1 " or " 0 ", which is then counted and stored in the register 38. Therefore, the electronic controller 20 reads the information stored in the register 38 so that the electronic controller 20 can know the number of channels, thereby performing the amplification control operation of the EDFA 9.

As described above, an output stabilization device corresponding to the number of channels of the wavelength division multiplexing optical fiber amplifier according to the features of the present invention may be configured.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. For example, in the description of the above embodiment, the optical splitter 31 and the channel number detector 30 are installed at the output terminal of the EDFA 9 to detect the number of channels through analysis of the output optical signal. This is because branching and measuring the optical signal amplified and output at a predetermined ratio is advantageous for measurement and error reduction compared to branching and measuring the weak optical signal since it is not yet amplified. However, in another embodiment of the present invention, the optical splitter 31 and the channel number detector 30 may be installed at the input terminal of the EDFA 9 to analyze the input optical signal.

As described above, the present invention partially splits an optical signal in order to stabilize an output according to a change in the number of channels of a wavelength division multiplexing optical fiber amplifier, and demultiplexes the split optical signal by wavelength bands set for each data channel. The number of channels currently used for transmission is analyzed, and the intensity of the output optical signal is controlled according to the number of channels identified. Therefore, the output can be stabilized immediately in response to the change in the number of channels. This reduces the time required to improve transmission quality.

Claims (12)

In the output stabilization method corresponding to the number of channels of the wavelength division multiplexing amplifier, Partly dividing the optical signal, Outputting the divided light by splitting and demultiplexing the split light into wavelength bands set for each data channel; Analyzing the light output for each wavelength band and checking the number of channels currently used for transmission; And controlling the intensity of the output optical signal according to the identified number of channels. The method of claim 1, wherein the splitting of the optical signal is partially performed. And stabilizing the optical signal amplified by the optical fiber amplifier. The process of claim 1, wherein the process of determining the number of channels currently used for transmission by analyzing light output for each wavelength band comprises: Converting each of the light output for each wavelength band into an electrical signal, comparing the level of each of the converted electrical signals with a preset reference level, and comparing the number of channels currently used for transmission by the comparison result value. Output stabilization method corresponding to the number of channels, characterized in that the step of determining. The method of claim 1, wherein the controlling of the intensity of the output optical signal according to the identified number of channels is performed. And controlling the intensity of the output optical signal to be maintained at a target value corresponding to the identified number of channels among the intensity target values of the preset output optical signal according to each channel number. In the output stabilization device according to the channel number change of the wavelength division multiplexing amplifier, An optical branch part for branching a predetermined amount from the output light of the optical fiber amplifier, A channel number detector for detecting the number of channels used for transmission by analyzing the light output for each data channel by demultiplexing the wavelength branched by the optical branch; And a control unit configured to receive information on the number of channels determined by the channel number detector and perform an amplification control operation corresponding thereto. The apparatus of claim 5, wherein the channel number detector is configured to demultiplex and output the light branched by the optical splitter into wavelength bands set for each data channel, and to output the light output for each wavelength band. And a photoelectric conversion unit for converting each electric signal into an electrical signal, and a comparison unit for outputting a result value indicating the presence or absence of a signal by comparing the level of each electrical signal converted by the photoelectric conversion unit with a preset reference level. Output stabilization device according to the change of the number of channels, characterized by determining whether the channel of the corresponding wavelength band using the presence or absence. In the output stabilization device according to the channel number change of the wavelength division multiplexing amplifier, An optical branching unit which is installed at a predetermined position on an optical signal path of the optical fiber amplifier and branches a predetermined amount from the light passing through; A demultiplexer for splitting and splitting the light branched by the optical splitter into wavelength bands set for each data channel; A photoelectric conversion unit for converting light output for each wavelength band into an electrical signal; A comparison unit comparing the level of each electrical signal converted by the photoelectric conversion unit with a preset reference level and outputting a result value thereof; A storage unit for storing the result value output from the comparison unit; And a control unit of an optical fiber amplifier configured to determine the number of channels through the information stored in the storage unit and perform an amplification control operation corresponding thereto. The apparatus of claim 7, wherein the demultiplexer comprises an optical waveguide grating. The apparatus of claim 7, wherein the photoelectric conversion unit comprises an array of a plurality of photodiodes provided one for each wavelength band. The apparatus of claim 7, wherein the comparator is provided with an electrical signal to one input terminal and receives a signal having a predetermined reference level as another input terminal, and compares the signal and outputs a comparison result for each electrical signal. Output stabilization device according to the change in the number of channels, characterized in that configuration. 11. The output stabilization apparatus according to any one of claims 7 to 10, wherein the optical signal path of the optical fiber amplifier in which the optical splitter is installed is an output terminal of the optical fiber amplifier. The apparatus of claim 10, wherein the storage unit is a shift register that counts a result of each of the operational amplifiers of the comparator.