CN107664792A - Optical signal generator, optical line terminal and the method for producing optical signal - Google Patents

Abstract

The present disclosure provides an optical signal generator, an optical line terminal and a method for generating an optical signal. According to an embodiment of the present disclosure, the optical signal generator includes: at least one optical circuit, including: a light source for generating an initial optical signal; a first arrayed waveguide grating for demultiplexing the initial optical signal into a plurality of sub-optical signals The second arrayed waveguide grating is used to multiplex a plurality of sub-optical signals into a first optical signal; and the first optical coupler is used to split the first optical signal into a second optical signal and a third optical signal, and the The second optical signal is output from at least one optical circuit, and the third optical signal is fed back to the light source.

Description

Optical signal generator, optical line terminal and method for generating optical signal

technical field

The present invention generally relates to the field of optical communication, and more specifically relates to an optical signal generator, an optical line terminal and a method for generating an optical signal.

Background technique

Ultra-broadband and its coexistence with existing technologies are basic requirements of network operators, and the evolution of passive optical networks (PON) will be implemented according to such basic requirements. Existing PONs such as GPON, EPON, and XG-PON are based on Time Division Multiplexing (TDM) technology. However, in the near future, new business models (such as home video editing, online gaming, interactive E-learning, telemedicine services, and next-generation 3D TV) will significantly increase bandwidth requirements. Next-generation PON (NG-PON) will solve the above-mentioned problems and also provide higher bandwidth and quality of service required for specific services. Further, time division wavelength division multiplexing passive optical network (TWDM-PON) by stacking a plurality of XG-PONs using wavelength division multiplexing (WDM) has been selected as a main way. The second way is to deploy a WDM PON that provides dedicated wavelength channels to individual Optical Network Units (ONUs) with different WDM transmit or receive technologies. In addition, more technologies, such as Orthogonal Frequency Division Multiplexing (OFDM) PON, 40Gbps TDMPON by adopting advanced modulation technology for Fiber-Wireless (Fi-Wi) access network and Radio over Fiber (RoF) may also be used in long-term evolution. Therefore, it is conceivable that a coexistence system including existing PON and NG-PON with various services will be produced.

Contents of the invention

In order to at least partly solve the above and other potential problems, embodiments of the present disclosure provide an optical signal generator, an optical line terminal, and a method for generating an optical signal.

In a first aspect of the present disclosure, an optical signal generator is provided. The optical signal generator includes: at least one optical circuit, including: a light source, used to generate an initial optical signal; a first arrayed waveguide grating, used to demultiplex the initial optical signal into multiple sub-optical signals; a second arrayed waveguide grating, for multiplexing a plurality of sub-optical signals into a first optical signal; and a first optical coupler for splitting the first optical signal into a second optical signal and a third optical signal, and splitting the second optical signal from at least one The optical loop outputs, and feeds back the third optical signal to the light source.

According to an embodiment of the present disclosure, at least one optical circuit includes a first optical circuit and a second optical circuit, wherein the central wavelength of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating in the first optical circuit and the second light Central wavelengths of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating in the loop are staggered from each other at predetermined intervals.

According to an embodiment of the present disclosure, the multi-wavelength optical generator further includes: a second optical coupler, configured to combine the second optical signal output by the first optical circuit and the second optical signal output by the second optical circuit into a fourth Optical signal for output from the optical signal generator.

According to an embodiment of the present disclosure, the first arrayed waveguide grating and the second arrayed waveguide grating in the first optical circuit and the second optical circuit both have 32 channels, and the first array in the first optical circuit and the second optical circuit The channel interval of the waveguide grating and the second arrayed waveguide grating is about 200 GHz, and the predetermined interval is about 100 GHz.

According to one embodiment of the present disclosure, the light source includes a semiconductor optical amplifier.

According to an embodiment of the present disclosure, the semiconductor optical amplifier is based on increasing the gain of the initial optical signal by increasing the bias current applied to the semiconductor optical amplifier.

According to one embodiment of the present disclosure, the bias current is about 100 mA.

According to an embodiment of the present disclosure, the 3dB bandwidth of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating is greater than 0.8nm.

In a second aspect of the present disclosure, an optical line terminal is provided. The optical line terminal includes: an optical signal generator according to the first aspect of the present disclosure; a demultiplexer, configured to demultiplex an optical signal output by the optical signal generator into a plurality of target optical signals; a plurality of modulators, It is used for modulating data into multiple target optical signals to generate multiple downlink optical signals; and a multiplexer is used for multiplexing the multiple downlink optical signals into a first downlink optical signal for sending to the optical network unit.

According to an embodiment of the present disclosure, the optical line terminal further includes: a distance extender, configured to increase the gain of the first downlink optical signal.

In a third aspect of the present disclosure, a method of generating an optical signal is provided. The method includes: at least one optical circuit: using a first arrayed waveguide grating to demultiplex an initial optical signal generated by a light source into a plurality of sub-optical signals; using a second arrayed waveguide grating to multiplex a plurality of sub-optical signals into a first light signal; use the first optical coupler to split the first optical signal into a second optical signal and a third optical signal; feed back the third optical signal to the light source; and output the second optical signal.

According to an embodiment of the present disclosure, at least one optical circuit includes a first optical circuit and a second optical circuit, wherein the central wavelength of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating in the first optical circuit and the second light Central wavelengths of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating in the loop are staggered from each other at predetermined intervals.

According to an embodiment of the present disclosure, the method further includes: combining the second optical signal output by the first optical circuit and the second optical signal output by the second optical circuit into a fourth optical signal; and outputting the fourth optical signal.

According to an embodiment of the present disclosure, the first arrayed waveguide grating and the second arrayed waveguide grating in the first optical circuit and the second optical circuit both have 32 channels, and the first array in the first optical circuit and the second optical circuit The channel interval of the waveguide grating and the second arrayed waveguide grating is about 200 GHz, and the predetermined interval is about 100 GHz.

According to an embodiment of the present disclosure, the method further includes: using a semiconductor optical amplifier as a light source.

According to an embodiment of the present disclosure, the method further includes: increasing the gain of the initial optical signal by increasing the bias current applied to the semiconductor optical amplifier.

According to an embodiment of the present disclosure, the method further includes: configuring the bias current to be 100mA.

According to an embodiment of the present disclosure, the method further includes: configuring the 3dB bandwidth of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating to be greater than 0.8 nm.

It will be understood from the following description that the optical signal generator and the optical signal generating method according to the present disclosure can be applicable to and support the coexistence of all modulation technologies and multi-generation multi-service PONs, and also support "pay for growth" (pay as you grow) network architecture. The corresponding benefits will be described in detail below.

Description of drawings

The present disclosure will be better understood and other objects, details, features and advantages of the present disclosure will become more apparent through the following description of specific embodiments of the present disclosure given with reference to the following drawings. In the attached picture:

FIG. 1 shows a schematic diagram of an optical signal generator 10 according to an embodiment of the present disclosure;

FIG. 2 shows a schematic diagram of an optical network architecture 20 according to an embodiment of the present disclosure;

FIG. 3 shows a schematic diagram of an optical signal generator 30 according to another embodiment of the present disclosure;

FIG. 4 shows a flowchart of a method 400 for generating an optical signal according to an embodiment of the present disclosure;

FIG. 5 shows a schematic diagram of the spectrum response of an arrayed waveguide grating with a spacing of 200 GHz according to an embodiment of the present disclosure;

6 shows a schematic diagram of the output spectrum of a dense WDM (DWDM) channel under different bias currents of a semiconductor optical amplifier according to an embodiment of the present disclosure;

FIG. 7 shows a schematic diagram of the output spectrum of the DWDM channel under different 3dB bandwidths of the arrayed waveguide grating according to an embodiment of the present disclosure;

FIG. 8 shows a schematic diagram of generating 64 DWDM wavelength channels according to an embodiment of the present disclosure;

Figure 9a shows a receive eye diagram of 2.5Gb/sOOK after 20km of single longitudinal mode fiber transmission according to one embodiment of the present disclosure;

Figure 9b shows a receive eye diagram of 10Gb/s OOK after 20km of single longitudinal mode fiber transmission according to yet another embodiment of the present disclosure;

Fig. 10 shows the reception spectrum of the 16QAMOFDM signal after 20km of single longitudinal mode fiber transmission according to another embodiment of the present disclosure; and

FIG. 11 shows a constellation diagram of a recovered 16QAM OFDM signal after 20 km of single longitudinal mode fiber transmission according to one embodiment of the present disclosure.

Detailed ways

Example embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain example embodiments of the present disclosure are shown in the drawings, it should be understood that the disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

As mentioned above, an optical signal generator is needed to generate a series of light sources and demultiplex them for different modulation techniques, so that the coexistence network formed can support traditional TDM PON (such as GPON, EPON, XGPON) and the following A generation of optical access networks (eg, NG-PON, mobile fronthaul). The inventor has noticed that existing solutions have many disadvantages.

An existing solution is to use WDM stacking. In the downlink, different PON traffic services are mixed together and transported on the same Optical Distribution Network (ODN). Coexistence is ensured by a coexistence element that multiplexes/demultiplexes the various wavelengths associated with each technology generation. Since the combined multiple generations of PON or services require different modulation techniques (eg, binary on-off keying format (OOK), quadrature amplitude modulation (QAM), and OFDM), external modulation with the seed light is required. This requires configuring high-quality services and a large number of light sources for each PON service.

Furthermore, the best way to provide light sources is to use multi-wavelength laser arrays, such as distributed feedback (DFB) lasers and Fabry-Perot (FP-LD) laser arrays. For coexistence systems, this is an alternative solution to provide a single coherent light source as an optical line terminal (OLT). However, fabricating high-performance multiwavelength laser arrays is not easy. First, the different lasers that are evenly spaced have to be defined side by side on the wafer side. This is often done by electron beam lithography, multiple quantum well (MQW) selective area growth and ridge width variation. Also, all of these techniques are difficult to achieve uniform wavelength spacing and may generate polygonal modes. Second, the emissions from the different laser elements should be collected into a single waveguide before being coupled to a single-mode fiber (SMF) for transmission in the PON. However, it is very difficult to achieve high coupling efficiency, so this will usually end up with low output power. Finally, wavelength accuracy and wavelength drift issues need to be overcome since the wavelength of DFB lasers is very sensitive to chip temperature.

On the other hand, the coexistence network system is designed to "pay as you grow" to allow operators to set up different technologies, and thus the whole WDM network usually requires a minimum of 64 wavelengths. This will obviously increase the difficulty of manufacturing the laser array and the cost of research and development.

Therefore, all these cases indicate that traditional solutions require high-quality service and a large number of light sources, have low coupling efficiency, are sensitive to temperature, and have high manufacturing and R&D costs. To at least partially address the above and other potential problems, embodiments of the present disclosure propose new optical signal generating devices and methods.

FIG. 1 shows a schematic diagram of an optical signal generator 10 according to an embodiment of the present disclosure. As shown in FIG. 1 , the optical signal generator 10 includes at least one optical circuit, and for clarity, only one optical circuit 105 is shown in FIG. 1 . The operating principles of the remaining unshown optical circuits are similar to the operating principles of this optical circuit.

The optical circuit 105 includes a light source 110 , a first arrayed waveguide grating 120 , a second arrayed waveguide grating 130 and a first optical coupler 140 . The light source 110 is used to generate an initial light signal. In an embodiment of the present disclosure, the light source 110 may be a broadband radiation light source with self-gain, such as a semiconductor optical amplifier (SOA). Thus, the initial optical signal emitted by the light source 110 has a broadband amplifier spontaneous emission (ASE) spectrum. In the case of using an SOA as the light source 110 , the gain of the initial optical signal can be increased by increasing the bias current applied to the SOA to overcome the loss in the optical circuit 105 . In one embodiment of the present disclosure, the bias current is about 100 mA. Of course, it should be understood that the above implementations are merely exemplary and any other suitable type of light source and/or bias current value may be used.

The first arrayed waveguide grating 120 demultiplexes the initial optical signal into a plurality of sub-optical signals. Here, the initial optical signal is split into multiple sub-optical signals by the first arrayed waveguide grating 120 in frequency spectrum. The interval of each sub-optical signal corresponds to the channel interval of the first arrayed waveguide grating 120 . Subsequently, the second arrayed waveguide grating 130 multiplexes the plurality of sub-optical signals into a first optical signal. In one embodiment of the present disclosure, the 3dB bandwidth of the channels of the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 is greater than 0.8nm. Further, the first optical coupler 140 splits the first optical signal into a second optical signal and a third optical signal, outputs the second optical signal from at least one optical circuit, and feeds back the third optical signal to the light source 110 .

Here, the optical circuit 105 forms an external laser resonant cavity, and after a stable state, stable coherent multi-wavelength laser light will be generated as optical signals of multiple wavelengths for subsequent use. Here, the stable state means that the gain of the light source and the loss of each component in the optical circuit reach a stable state.

In addition, in the case where the optical signal generator 10 includes a plurality of optical circuits, the central wavelengths of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating in each optical circuit are relative to the first array waveguide gratings in other optical circuits. Central wavelengths of the channels of the waveguide grating and the second arrayed waveguide grating are shifted from each other at predetermined intervals.

For example, consider two optical circuits included in the optical signal generator 10, referred to as a first optical circuit and a second optical circuit. The central wavelength of the channels of the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 in the first optical circuit and the central wavelength of the channels of the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 in the second optical circuit are The predetermined intervals are staggered from each other.

FIG. 2 shows a schematic diagram of an optical network architecture 20 according to an embodiment of the present disclosure. As shown in FIG. 2 , optical network architecture 20 includes at least one optical line terminal (OLT) 210 , wavelength switching router 240 , remote node 245 and a plurality of optical network units (ONUs) 255 , 260 and 265 .

The connections and quantities of the above-mentioned components are only shown as examples, and those skilled in the art should understand that the above-mentioned numbers are only examples and not limiting. For example, although only three ONUs are shown in FIG. 2 , any number of ONUs can be configured according to actual needs.

Included in the OLT 210 shown in FIG. 2 is an optical signal generator 215 according to the present disclosure, which is, for example, the optical signal generator 10 described with reference to FIG. 1 . In addition, the OLT 210 also includes a demultiplexer 220 , at least one modulator 225 , and a multiplexer 230 .

The optical signal generator 215 will generate multi-wavelength optical signals. The multi-wavelength optical signal is demultiplexed into a plurality of target optical signals via the demultiplexer 220 . In an embodiment of the present disclosure, the demultiplexer 220 may be, for example, an arrayed waveguide grating, and the number of channels of the arrayed waveguide grating is consistent with the number of target optical signals.

These target optical signals are then provided to at least one modulator 225 . The types of these modulators 225 may be the same or different from each other. For example modulator 225 may be an I/Q modulator, an intensity modulator or an analog modulator. And different modulators 225 can also be used to modulate different types of data, such as OFDM, OOK and so on. These modulators are used to modulate data into multiple target optical signals to generate multiple downstream optical signals. Next, the multiplexer 230 multiplexes the multiple downlink optical signals into a first downlink optical signal for sending to the ONU.

In an embodiment of the present disclosure, the OLT 210 may further include a distance extender 235 for increasing the gain of the first downlink optical signal, thereby increasing the transmission distance of the first downlink optical signal. In one embodiment of the present disclosure, the distance extender 235 may include at least one of an optical fiber amplifier (EDFA), an SOA, and a wave shaper.

The first downlink optical signal as an output of the OLT 210 will be delivered to a different remote node 245 , for example via a wavelength switching router 240 . Then, it is further delivered to a plurality of ONUs 255 , 260 and 265 through the optical splitter 250 in the remote node 245 . These ONUs can be based on the same technology or different technologies. For example, ONU 255 is a GPONONU, ONU 260 is an XGPON ONU, and ONU 265 is an NG-PON ONU. Therefore, the optical signal generator according to the present disclosure can be applied to modulation modes, data types, PON services and ONUs of different technical types, so that it can be used in an environment where multiple generations of technologies coexist.

FIG. 3 shows a schematic diagram of an optical signal generator 30 according to another embodiment of the present disclosure. The optical signal generator 30 shown in FIG. 3 may be used as the optical signal generator in the OLT 210 in FIG. 2 to generate multi-wavelength optical signals. The optical signal generator 30 shown in FIG. 3 has a first optical circuit 105 , a second optical circuit 305 and a second optical coupler 310 .

In this implementation, the first optical circuit 105 includes a light source 110 , a first arrayed waveguide grating 120 , a second arrayed waveguide grating 130 and a first optical coupler 140 . The second optical circuit 305 includes a light source 110 , a first arrayed waveguide grating 120 , a second arrayed waveguide grating 130 and a first optical coupler 140 .

In this embodiment, the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 having 32 channels are exemplarily used in the first optical circuit 105 and the second optical circuit 305 . Moreover, the channel intervals of the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 are both about 200 GHz. In addition, the central wavelengths of the channels of the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 in the first optical circuit 105 and the channels of the first arrayed waveguide grating 120 and the second arrayed waveguide grating 130 in the second optical circuit 305 The central wavelengths of the wavelengths are staggered from each other at a predetermined interval of about 100GH.

As mentioned above, the two light sources 110 in the first optical circuit 105 and the second optical circuit 305 may be a broadband radiation source with self-gain, such as SOA. Thus, the initial optical signal emitted by the light source 110 has a broadband amplifier spontaneous emission (ASE) spectrum.

As shown in FIG. 3 , for the first optical circuit 105 , the first arrayed waveguide grating 120 demultiplexes the initial optical signal into 32 sub-optical signals ( Ch1 , Ch3 . . . Ch63 ). Subsequently, the second arrayed waveguide grating 130 multiplexes the 32 sub-optical signals (Ch1, Ch3...Ch63) into a multi-wavelength first optical signal. Here, the first optical signal has 32 wavelengths (the wavelengths are shown in the figure as a block diagram with different lines). The first optical coupler 140 splits the first optical signal into a second optical signal and a third optical signal, outputs the second optical signal from the first optical circuit 105 , and feeds back the third optical signal to the light source 110 . As mentioned above, the first optical circuit 105 forms a laser resonant cavity, and after a stable state, stable coherent laser light will be generated as optical signals of multiple wavelengths for subsequent use.

Similarly, for the second optical circuit 305, the first arrayed waveguide grating 120 demultiplexes the initial optical signal into 32 sub-optical signals (Ch2, Ch4...Ch64). Subsequently, the second arrayed waveguide grating 130 multiplexes the 32 sub-optical signals (Ch2, Ch4...Ch64) into a multi-wavelength first optical signal. Here, too, the first optical signal in the second optical circuit 305 has 32 wavelengths (these wavelengths are shown in the figure as blocks with different lines). The first optical coupler 140 splits the first optical signal into a second optical signal and a third optical signal, outputs the second optical signal from the second optical circuit 305 , and feeds back the third optical signal to the light source 110 . Similarly, the second optical circuit 305 forms a laser resonant cavity, and after a stable state, stable coherent laser light will be generated as optical signals of multiple wavelengths for subsequent use.

The second optical coupler 310 combines the second optical signal from the first optical circuit 105 and the second optical signal from the second optical circuit 305 into a fourth optical signal to be output from the optical signal generator 30 . As shown in the figure, the optical signal finally output by the optical signal generator 30 has 64 wavelengths (these wavelengths are shown in a block diagram with different lines in the figure), and the respective wavelengths are spaced apart from each other by 100 GHz.

In this embodiment, the central wavelengths of the channels of the arrayed waveguide gratings in the first optical circuit 105 and the second optical circuit 305 are staggered by 100 GHz, and the outputs of the two optical circuits are combined through the second optical coupler 310 . This doubles the sum of the number of all wavelengths and it fully meets the Dense WDM (DWDM) International Telecommunication Union (ITU) standard.

Those skilled in the art should understand that although the embodiment of FIG. 3 shows the implementation of two optical circuits, the above description is only exemplary and not limiting. An optical signal generator according to the present disclosure may include any number of optical circuits, and the principle of operation of two optical circuits described herein may be extended to any desired number of optical circuits. For example, in the embodiment of FIG. 3 , optical signals with 64 wavelengths are generated, and by setting a required number of optical circuits, the number of wavelengths of optical signals output by the optical signal generator can be expanded. Similarly, all numerical values described above are exemplary only and are not intended to limit the scope of the present disclosure in any way.

FIG. 4 shows a flowchart of a method 400 for generating an optical signal according to an embodiment of the present disclosure. The method in FIG. 4 will be described below in conjunction with FIG. 1 , and the method in FIG. 4 is implemented at at least one optical circuit 105 .

At 410, the initial optical signal generated by the light source 110 is demultiplexed into a plurality of sub-optical signals by using the first arrayed waveguide grating 120 . At 420, the multiple sub-optical signals are multiplexed into a first optical signal by using the second arrayed waveguide grating 130 . At 430, the first optical signal is split into a second optical signal and a third optical signal using the first optical coupler 140 . At 440 , the third light signal is fed back to the light source 110 . At 450, a second optical signal is output.

Although FIG. 4 only shows several steps of the method 400, it should be understood that the method 400 may also include several optional steps not shown. For example, in some embodiments, at least one optical circuit includes a first optical circuit and a second optical circuit, wherein the central wavelength of the channels of the first AWG and the second AWG in the first optical circuit and the second Central wavelengths of channels of the first arrayed waveguide grating and the second arrayed waveguide grating in the optical circuit are staggered from each other at predetermined intervals.

In some embodiments, the method further includes combining the second optical signal output by the first optical circuit and the second optical signal output by the second optical circuit into a fourth optical signal; and outputting the fourth optical signal. In some embodiments, both the first arrayed waveguide grating and the second arrayed waveguide grating in the first optical circuit and the second optical circuit have 32 channels, and the first arrayed waveguide grating in the first optical circuit and the second optical circuit The channel spacing of the grating and the second arrayed waveguide grating is about 200 GHz, and the predetermined spacing is about 100 GHz.

In some embodiments, the method further includes using a semiconductor optical amplifier as the light source. In some embodiments, the method further includes increasing the gain of the initial optical signal by increasing a bias current applied to the semiconductor optical amplifier. In some embodiments, the method further includes: configuring the bias current to be 100 mA. In some embodiments, the method further includes: configuring the 3dB bandwidth of the channels of the first arrayed waveguide grating and the second arrayed waveguide grating to be greater than 0.8 nm.

Various advantages of the optical signal generator according to the present disclosure and benefits brought by various components will be verified below with reference to the accompanying drawings. To this end, a detailed experimental approach is implemented to simulate multiple PON services. As will be detailed below, the optical signal generated by the optical signal generator as a multi-wavelength light source is capable of 10Gb/s OOK, 10Gb/s 16QAM with no bit error rate on the transmission of a single longitudinal mode (SMF) fiber over 20km And 10Gb/s OFDM modulation. This shows that the proposed light source can support all PON services from traditional TDM/TWDM/WDM PON to advanced OFDM PON and mobile fronthaul services.

In some embodiments of the present disclosure, arrayed waveguide gratings (such as the first arrayed waveguide gratings 330 and 340 and the second arrayed waveguide gratings 350 and 360 in FIG. 3 ) with a channel spacing of 200 GHz are used in the optical signal generator. . The reason for using this arrayed waveguide grating is to significantly increase the 3dB bandwidth of each wavelength channel, thereby allowing more light to pass through the channel of the arrayed waveguide grating. Therefore, in the aforementioned external laser resonator, the total gain exceeds the total loss, thereby increasing the laser intensity.

In contrast, if a conventional arrayed waveguide grating with 100 GHz channel spacing is used, no lasing is produced and only incoherent ASE noise sliced across the spectrum is obtained. The reason is that such light sources are too broad for telecommunication and can only be used for sending low-power signals.

FIG. 5 shows a schematic diagram of the spectrum response of an arrayed waveguide grating with a spacing of 200 GHz according to an embodiment of the present disclosure. As shown in Fig. 5, the channel spacing is 200GHz (or ≈1.6nm), the 3dB bandwidth of each channel is 1nm and the channel compression ratio is 20dB. Further, this arrayed waveguide grating is easy to manufacture. Compared to Gaussian or triangular channel responses, the channel response of flat-top AWGs is better because lasing is easier. This issue will be elaborated below.

FIG. 6 shows a schematic diagram of the output spectrum of a dense WDM (DWDM) channel under different bias currents of a semiconductor optical amplifier according to an embodiment of the present disclosure. The output spectrum at different bias currents is shown with different lines in FIG. 6 . Here, an ITU DWDM channel (Ch. 20, 1561.42nm) is selected as the DWDM channel for example. As shown in Figure 6, at low SOA bias current (20mA), the output spectrum is sliced ASE noise with the same shape as the channel of the arrayed waveguide grating. However, as the SOA bias current increases, the lasing rises due to the overall gain increase in the outer laser resonator. When the SOA is biased at 100mA, a maximum output power around -5dBm is obtained with a corresponding SNR of 65dB.

Fig. 7 shows a schematic diagram of the output spectrum of the DWDM channel under different 3dB bandwidths of the arrayed waveguide grating according to an embodiment of the present disclosure. Similarly, an ITU DWDM channel (Ch.20, 1561.42nm) is exemplarily selected as the DWDM channel. In addition, in the example of Fig. 7, the bias current of SOA is 100mA. Here, the output spectrum at different 3dB bandwidths of the arrayed waveguide grating is shown with different lines.

As shown in Fig. 7, when the 3dB bandwidth of the arrayed waveguide grating is greater than 0.8nm, lasing is generated and the peak power remains stable regardless of the 3dB bandwidth of the subsequent channel. As shown in Figure 7, the central wavelength is red-shifted at the 3dB bandwidth of the larger channel due to the crossover gain due to the interaction between the multiple longitudinal modes. A spectral redshift indicates that the long-wavelength mode experiences higher optical gain. Therefore, it is better to use a flat-top AWG than a Gaussian-shaped AWG. This is because, if a Gaussian-shaped arrayed waveguide grating is used, the red shift is affected by a large frequency response attenuation caused by the long-wavelength falling edge of the Gaussian-shaped arrayed waveguide grating. The flat-top arrayed waveguide grating can just avoid the above problems.

Fig. 8 shows a schematic diagram of generating 64 DWDM wavelength channels according to an embodiment of the present disclosure. In Fig. 8, two sets of 1:32 arrayed waveguide gratings with a channel spacing of 200 GHz and a 3 dB channel bandwidth of 1 nm are used to generate a total of 64 coherent light sources. This can be achieved, for example, by the optical signal generator 30 shown in FIG. 3 . For example, 32 wavelengths (shown in solid lines in FIG. 8 ) are produced by the first optical circuit of the optical signal generator 30, and the remaining 32 wavelengths (in FIG. shown in dotted line).

A total of 64 wavelengths are thus obtained. All of these wavelength channels have a moderate power of -5dBm and a very high SNR above 65dB. Because arrayed waveguide gratings (such as the first arrayed waveguide gratings 120, 330, and 340) are used to determine the wavelength spacing in the present disclosure and because arrayed waveguide gratings are not sensitive to temperature, it is possible to compare the multi-wavelength laser arrays in the prior art. Significantly improve wavelength accuracy and wavelength drift problems.

Further, as shown in FIG. 8 , the entire wavelength range of the generated multi-wavelength optical signal is from 1525 nm to 1575 nm, which completely covers the C bandwidth. In addition, as mentioned before, the total number of wavelength channels can also be improved by adopting higher ratio AWGs, and this will meet all existing downlink wavelength standards of PON services and NG-PON services.

The signal modulation performance of the optical signal generators according to the present disclosure (such as the optical signal generators 10 and 30 ) will be further illustrated below with reference to the accompanying drawings. Here, one of the optical signals/light sources generated by the optical signal generator is selected and a modulator (such as modulator 230 in FIG. 2 ) is used to modulate the OOK data signal and the OFDM data signal thereon to emulate a conventional TDM PON and NG-PON services. Figure 9a shows a receive eye diagram of a 2.5Gb/s OOK after 20km of single longitudinal mode fiber transmission according to one embodiment of the present disclosure. Fig. 9b shows a receive eye diagram of a 10Gb/s OOK after 20km of single longitudinal mode fiber transmission according to yet another embodiment of the present disclosure.

As shown in Figures 9a and 9b, with an optimal receiver sensitivity of -28dBm, both eye diagrams remain unrolled and open, and the measured bit error rate is less than 10 ^-9 . This transfer performance is comparable to that of a DFB+electroabsorption modulator (EAM) configuration and does not require a temperature control mechanism. Further cost savings can thereby be achieved.

Further, OFDM transmission performance is also measured by modulating 2.5GHz 16QAM OFDM signal. FIG. 10 shows the received spectrum of a 16QAM OFDM signal after 20 km of single longitudinal mode fiber transmission according to another embodiment of the present disclosure. FIG. 11 shows a constellation diagram of a recovered 16QAMOFDM signal after 20 km of single longitudinal mode fiber transmission according to one embodiment of the present disclosure. As shown in Figure 10, the recovered spectrum is extremely clear without being disturbed by noise, and the signal constellation diagram in Figure 11 is also clear. The average error vector magnitude in the OFDM signal is lower than 12.5% in the case of the best receiver sensitivity of -20dBm.

Therefore, the above experimental results show that the proposed optical signal generator can provide a large number of high-quality light sources, which can be used for the modulation of all services in the coexistence situation of the multi-service PON system.

The disclosure proposes an optical signal generator, an optical line terminal and a method for generating an optical signal. The proposed scheme has at least the following advantages: 1) It is applicable to the coexistence of all modulation technologies and multi-generation multi-service PON; 2) It supports the network architecture of "pay as you grow"; 3) It can provide multiple coherent light source. Further, compared with traditional solutions, the advantages of this solution are at least: 1) easy to manufacture and easy centralized control/management; 2) low cost and low power consumption: in this solution, only SOA is an active component, AWG and optical coupler are passive components; 3) achieve precise wavelength spacing; 4) are insensitive to temperature and have no wavelength drift problem; 5) achieve ultra-high SNR.

The future PON evolution needs to inherit the existing PON ODN architecture. This will cause the coexistence of multi-service PONs with different modulation techniques in the same ODN network. A high-performance multi-wavelength light source will become very important, and the present disclosure at least addresses the above-mentioned problems.

In one or more exemplary designs, the functions of the present application may be implemented by hardware, software, firmware or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. Storage media may be any available media that can be accessed by a general purpose or special purpose computer. Such computer-readable media may include, for example and without limitation, RAM, ROM, EEPROM, CD-ROM, or other optical disk storage, magnetic disk storage, or other magnetic Any other medium that carries or stores desired modules of program code in the form of instructions or data structures accessible to a processor. Also, any connection is also termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial Cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are also included in the definition of media.

A general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components or used to implement the The various exemplary logical blocks, modules, and circuits described in connection with this disclosure are implemented or performed in any combination of the functions of the present disclosure. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such architecture.

Those of ordinary skill in the art should also understand that various exemplary logical blocks, modules, circuits and algorithm steps described in conjunction with the embodiments of the present application may be implemented as electronic hardware, computer software or a combination of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functions in various ways for each specific application, but such implementation decisions should not be interpreted as departing from the protection scope of the present disclosure.

The above description of the present disclosure is provided to enable any person of ordinary skill in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other modifications without departing from the spirit and scope of the present disclosure. Thus, the disclosure is not to be limited to the examples and designs herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (18)

1. a kind of optical signal generator, including：

At least one light circuit, including：

Light source, for producing initial optical signal；

First array waveguide grating, for the initial optical signal to be demultiplexed into multiple sub-light signals；

Second array waveguide grating, for by the multiple sub-light signal multiplexing into the first optical signal；And

First photo-coupler, for first optical signal to be shunted into the second optical signal and the 3rd optical signal, by described second Optical signal exports from least one light circuit, and by the 3rd optical signal feedback to the light source.

2. optical signal generator according to claim 1, wherein at least one light circuit include the first light circuit and Second light circuit, the passage of first array waveguide grating and second array waveguide grating in first light circuit Central wavelength and second light circuit in first array waveguide grating and second array waveguide grating it is logical The central wavelength in road mutually staggers at a predetermined interval.

3. optical signal generator according to claim 2, wherein the multi-wavelength light generator also includes：

Second photo-coupler, exported for second optical signal for exporting first light circuit and second light circuit Second optical signal be merged into the 4th optical signal so as to from the optical signal generator export.

4. optical signal generator according to claim 3, wherein in first light circuit and second light circuit First array waveguide grating and second array waveguide grating are respectively provided with 32 passages, first light circuit and described The channel spacing of first array waveguide grating and second array waveguide grating in second light circuit is about 200GHz, And the predetermined space is about 100GHz.

5. optical signal generator according to claim 1, wherein the light source includes semiconductor optical amplifier.

6. optical signal generator according to claim 5, wherein the semiconductor optical amplifier is based on applying by increasing Bias current on the semiconductor optical amplifier improves the gain of the initial optical signal.

7. optical signal generator according to claim 6, wherein the bias current is about 100mA.

8. optical signal generator according to claim 1, wherein first array waveguide grating and second array The three dB bandwidth of the passage of waveguide optical grating is more than 0.8nm.

9. a kind of optical line terminal, including：

Optical signal generator according to any one of claim 1 to 8；

Demultiplexer, the optical signal for the optical signal generator to be exported demultiplex into multiple target optical signals；

Multiple modulators, for modulating data on the multiple target optical signal to produce multiple downlink optical signals；And

Multiplexer, for the multiple downlink optical signal to be multiplexed into the first downlink optical signal to be sent to optical network unit.

10. optical line terminal according to claim 1, in addition to：

Range extender, for improving the gain of first downlink optical signal.

11. a kind of method for producing optical signal, including：

At at least one light circuit：

Initial optical signal caused by light source is demultiplexed into multiple sub-light signals using the first array waveguide grating；

Using the second array waveguide grating by the multiple sub-light signal multiplexing into the first optical signal；

First optical signal is shunted to the second optical signal and the 3rd optical signal using the first photo-coupler；

By the 3rd optical signal feedback to the light source；And

Export second optical signal.

12. according to the method for claim 11, wherein at least one light circuit includes the first light circuit and the second light Loop, wherein the passage of first array waveguide grating and second array waveguide grating in first light circuit The passage of first array waveguide grating and second array waveguide grating in central wavelength and second light circuit Central wavelength mutually stagger at a predetermined interval.

13. according to the method for claim 12, wherein methods described also includes：

By second optical signal of first light circuit output and second optical signal of second light circuit output It is merged into the 4th optical signal；And

Export the 4th optical signal.

14. according to the method for claim 13, wherein in first light circuit and second light circuit described the An array waveguide optical grating and second array waveguide grating are respectively provided with 32 passages, first light circuit and second light The channel spacing of first array waveguide grating and second array waveguide grating in loop is about 200GHz, and institute It is about 100GHz to state predetermined space.

15. according to the method for claim 11, methods described also includes：

The light source is used as by the use of semiconductor optical amplifier.

16. according to the method for claim 15, methods described also includes：

Bias current on the semiconductor optical amplifier is applied to improve the gain of the initial optical signal by increase.

17. according to the method for claim 16, methods described also includes：

The bias current is configured to 100mA.

18. according to the method for claim 11, methods described also includes：

The three dB bandwidth of first array waveguide grating and the passage of second array waveguide grating is configured to be more than 0.8nm。