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CN107395288B - A polarization diversity optical heterodyne coherent receiving method and system - Google Patents

A polarization diversity optical heterodyne coherent receiving method and system Download PDF

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CN107395288B
CN107395288B CN201710607170.XA CN201710607170A CN107395288B CN 107395288 B CN107395288 B CN 107395288B CN 201710607170 A CN201710607170 A CN 201710607170A CN 107395288 B CN107395288 B CN 107395288B
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CN107395288A (en
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张帆
朱逸萧
陈泽宇
李艳萍
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Peking University
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
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    • H04B10/616—Details of the electronic signal processing in coherent optical receivers
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Abstract

本发明公开了一种偏振分集的光外差相干接收方法及系统。本系统的接收端包括：偏振分集外差接收机模块，用于对偏振复用信号光分束，得到X单偏振信号和Y单偏振信号；对本振光进行分束，得到两束本振光；然后将一束本振光与X单偏振信号合束并对合束后的信号进行功率检测得到X单偏振信号的电信号，将另一束本振光与Y单偏振信号合束并对合束后的信号进行功率检测得到Y单偏振信号的电信号；连接偏振分集外差接收机模块的信号‑信号拍频干扰补偿模块，连接信号‑信号拍频干扰补偿模块的下变频模块，连接下变频模块的奈奎斯特滤波模块；联合均衡模块，用于均衡两个偏振的光信号，然后输出解调信号。本发明结构简单且在误码率性能上接近平衡探测。

Figure 201710607170

The invention discloses a polarization diversity optical heterodyne coherent receiving method and system. The receiving end of the system includes: a polarization diversity heterodyne receiver module, which is used to split the polarization multiplexed signal light to obtain an X single-polarized signal and a Y single-polarized signal; split the local oscillator light to obtain two beams of local oscillator light Then combine a beam of local oscillator light and X single-polarization signal and perform power detection on the combined signal to obtain the electrical signal of X single-polarization signal, combine another beam of local oscillator light and Y single-polarization signal and perform power detection. Perform power detection on the combined signal to obtain the electrical signal of the Y single-polarization signal; connect the signal-signal beat frequency interference compensation module of the polarization diversity heterodyne receiver module, connect the down-conversion module of the signal-signal beat frequency interference compensation module, connect The Nyquist filter module of the down-conversion module; the joint equalization module is used to equalize the two polarized optical signals, and then output the demodulated signal. The present invention has a simple structure and is close to balanced detection in bit error rate performance.

Figure 201710607170

Description

Polarization diversity optical heterodyne coherent receiving method and system
Technical Field
The invention belongs to the field of optical communication, relates to a method and a system based on optical heterodyne coherent reception, and particularly relates to a receiving end demodulation method based on Nyquist matching filtering, and a corresponding receiver structure and a corresponding system.
Background
The coherent optical communication system has the advantages of high sensitivity and long transmission distance, and is an important solution for medium and long distance optical fiber communication transmission systems. Coherent optical communication systems can be divided into homodyne detection and heterodyne detection. The homodyne detection system sets the frequency of the local oscillation light to be the same as the frequency of the signal optical carrier, and the frequency of the local oscillation light of the heterodyne detection system has a frequency offset from the frequency of the signal optical carrier.
A coherent receiver, which is common in optical communication systems at present, includes an optical coupler, a polarization-controlled beam splitter, a mixer, and an optical detector. Homodyne coherent receivers have been described in a number of documents and patents. For each polarization signal, an optical mixer and two balanced photodetectors are usually required to implement in-phase and quadrature two-path reception demodulation of the signal. It can be seen that such a configuration results in a system with a large number of components, relatively large size, and relatively high cost. It is to be appreciated that this invention is susceptible to further improvements and innovations.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention aims to provide a scheme of a heterodyne receiver for polarization diversity, and a structure and a system for realizing the method.
In order to achieve the purpose, the invention adopts the following technical scheme:
a polarization multiplexing modulation mode based on Nyquist filtering comprises the following steps:
the first step is as follows: determining the baud rate of the modulation signal according to the bandwidth of each device of the system;
the second step is that: light from a light source is divided into two paths through a coupler of 50:50, X and Y polarization signals are respectively modulated, the main content comprises mapping from a binary sequence to a constellation diagram symbol, a frame leader sequence and Nyquist shaping filtering are added, and the two paths are combined into one path through a polarization beam combiner to form a polarization multiplexing light modulation signal (namely the polarization multiplexing signal light input into a receiver in the figure 1);
the third step: the polarization-multiplexed signal light is received at a receiving end. The local oscillator light is adjusted to a proper frequency (generally required: 1) which is slightly larger than a half of the baud rate of the signal light, and the signal light is ensured to be on one side of the local oscillator light; 2) the method comprises the steps of subtracting half of a signal baud rate from a receiver photoelectric detector bandwidth, ensuring that signal light does not exceed the photoelectric detector bandwidth after being converted into an electric signal, splitting local oscillator light by using a light splitter, splitting signal light by using a polarization beam splitter, and then combining the local oscillator light and the signal light by using an optical coupler (as long as two coupled beams of light keep the same polarization direction, wherein the two coupled beams of light can be combined by using an optical combiner (as shown in figure 4) or a 1 × 2MMI interferometer (as shown in figure 5)), so as to form a polarization diversity optical heterodyne receiving scheme.
Further, the signal at the transmitting end is preprocessed before the polarization beam combiner, and the preprocessing comprises modulator nonlinear precompensation, dispersion precompensation or fiber Kerr nonlinear precompensation.
Further, signal-signal beat frequency damage generated by square law detection of a single-ended Photoelectric Detector (PD) is eliminated by utilizing an iterative algorithm in Digital Signal Processing (DSP) for a receiving end signal.
An optical heterodyne coherent receiving system for implementing the method comprises a transmitting end and a receiving end,
the transmitting end includes:
the transmitting end Nyquist filtering module is used for compressing the frequency spectrum to be close to a square under the condition of ensuring that the receiving end has no intersymbol interference (ISI), and improving the frequency spectrum utilization rate; (the maximum signal-to-noise ratio can be achieved using the same pair of filters for the originating and receiving ends.
The receiving end includes:
an optical filter module for removing unwanted out-of-band information;
a polarization diversity heterodyne receiver module. The polarization multiplexing optical signal is used for separating X, Y single polarization signal light and then respectively converting the signal light into two paths of electric signals through a single-ended photoelectric detector. The system specifically comprises the following six modules:
the signal optical coupling module is connected with the optical filter module and used for realizing the coupling of the signal light from the transmission optical fiber to the receiving system;
the polarization beam splitting module is connected with the signal light coupling module and used for realizing polarization beam splitting of the signal light;
the local oscillator optical coupling module is used for realizing the coupling of local oscillator light from the laser to a receiving system;
the optical splitter module is connected with the local oscillator optical coupling module and used for realizing uniform beam splitting of local oscillator light;
the optical beam combiner module is connected with the polarization beam splitting module and the optical beam splitter module and used for combining the signal light and the local oscillator light;
the single-ended optical detector module is connected with the optical beam combiner module and used for realizing the optical power detection after beam combination;
the signal-signal beat frequency interference compensation module is connected with the single-ended optical detector module and is used for compensating signal-signal beat frequency interference (SSBI);
the down-conversion module is connected with the signal-signal beat frequency interference compensation module and is used for converting the electric signal received by the Photoelectric Detector (PD) into a baseband signal;
and the receiving end Nyquist filtering module is connected with the down-conversion module and is used for eliminating intersymbol interference (ISI) and improving the signal-to-noise ratio.
And the joint equalization module is used for simultaneously equalizing the two polarized optical signals and then outputting and demodulating.
Further, still include:
and the transmitting end modulation module is used for mapping the original binary sequence in a modulation format (such as a quadrature amplitude phase modulation (QAM) format) and inserting the synchronization series and the training sequence as a frame structure preamble sequence.
And the transmitting terminal preprocessing module is used for preprocessing the transmitting terminal signal and then sending the signal to the communication channel.
And the receiving end demodulation module is used for carrying out optimal sampling point optimization and X-Y polarization 2X2 combined channel equalization on the sequence after the receiving end matched filtering, and judging and demodulating the sequence back to a binary sequence.
Further, the preprocessing performed by the front-end data processing module includes: nonlinear compensation of a modulator, dispersion pre-compensation and Kerr nonlinear compensation of optical fibers.
Compared with the prior art, the invention has the following positive effects:
the method combines an iterative cancellation signal-signal beat frequency interference compensation algorithm under the condition of heterodyne coherent detection, provides a heterodyne coherent receiver structure and an algorithm based on a single-ended photoelectric detector, and realizes the receiving of polarization multiplexing signals. Compared with the traditional coherent optical receiver with a balanced optical detector, the invention utilizes the single-ended optical detector, has the characteristics of simple structure, small size and low cost, and can approach to balanced detection in the aspect of error rate performance.
Drawings
Fig. 1 is a block diagram of an overall receiving system of an embodiment of the present invention.
Fig. 2 is a flowchart of a digital signal processing method based on polarization diversity heterodyne coherent reception according to an embodiment of the present invention.
Fig. 3 is a detail of the flow of X-Y polarization joint equalization in the digital signal processing method module.
Fig. 4 is a schematic diagram of a receiver portion of an embodiment of the invention.
FIG. 5 is a diagram of an implementation of a receiver portion of an embodiment of the invention, an on-chip integrated heterodyne coherent receiver.
Detailed Description
The present invention will be described in further detail below with reference to specific examples and the accompanying drawings.
Fig. 1 is a block diagram of the overall receiving system of the present embodiment, which is composed of a receiver structure and a subsequent digital signal processing section; see figures 2, 3, 4, 5 for details.
The following describes the implementation of the technical solution in detail with reference to the algorithm flow chart 2 of this embodiment.
The first step is as follows: determining the baud rate of the transmitted IQ signal according to the system frequency bandwidth;
and secondly, carrying out Nyquist filtering with roll-off coefficient α at the transmitting end, wherein the purpose is to compress the spectrum of the IQ signal into an approximate square, and generally α can be ensured to be 0.01.
Before being transmitted to a communication channel, the signal is typically dispersion pre-compensated in the frequency domain:
Spre(f)＝S(f)·exp(-β2Lω2/2),
wherein S ispre(f) Is the frequency domain data after pre-compensation, S (f) is the frequency domain data before pre-compensation, β2And L is the length of the optical fiber, and omega is the angular frequency of each frequency point on the signal frequency domain relative to the local oscillator light.
The third step: optical filtering is first performed at the receiving end. Filtering noise outside a signal bandwidth; the received polarization multiplexing signal light is divided into two paths of X and Y single polarization signals after passing through a polarization beam splitter or a two-dimensional grating; mixing each polarized signal (X and Y single-polarized signals) with a local oscillator respectively, and detecting the signals by a single-ended optical detector to obtain an electric signal of the X single-polarized signal and an electric signal of the Y single-polarized signal; then, in the signal-signal beat frequency interference compensation module, firstly compensating the signal-signal beat frequency interference generated by the single-ended photoelectric detector:
Figure BDA0001358609630000041
wherein
Figure BDA0001358609630000042
For the interference-compensated signal, ri(t) represents the received local oscillator light and signal light beat frequency signal, λ is the amplitude factor dependent on the local oscillator light and signal light power ratio, and Hilbert (·) represents Hilbert transform. This process may be iterated multiple times to gradually improve performance, typically substantially stabilizing after 4 to 6 times. Since this process does not involve decision demodulation, the computational complexity is low.
The resulting signal is then down-converted:
Figure BDA0001358609630000043
the signal after down conversion is then nyquist matched filtered.
And finally, demodulating a receiving end, including optimizing an optimal sampling point, carrying out 2 multiplied by 2 combined channel equalization on the X-Y polarization, compensating the polarization mode dispersion of the optical fiber channel, and carrying out polarization rotation, judgment and demodulation between the transmitting end and the receiving end.
Fig. 3 is a schematic diagram of an X-Y polarization joint channel equalization process, in which X, Y two polarization signal inputs undergo 2X2 Multiple Input Multiple Output (MIMO) joint equalization to obtain polarization mode dispersion of a compensation fiber channel and X, Y polarization output after polarization rotation between the transceiving ends. Where the MIMO part consists essentially of four transfer functions, X to X, X to Y, Y to X, Y to Y.
Fig. 4 is a schematic diagram of a receiver portion. The signal light is coupled to a system and is subjected to polarization beam splitting to form a first light beam and a second light beam; the local oscillation light is coupled to the system, is divided into two paths by the beam splitter, is respectively combined with the first signal beam and the second signal beam, enters the optical detector for detection, and obtains an electric signal of an X single-polarization signal and an electric signal of a Y single-polarization signal.
FIG. 5 shows a schematic diagram of an on-chip integrated heterodyne receiver as an implementation of the receiver architecture. The structure comprises a two-dimensional coupling grating, a one-dimensional coupling grating, a 1 x2 multimode interference (MMI) beam splitter, two 2x 2MMI interferometers and two silicon germanium light detectors. The polarization multiplexing signal light is coupled to the sheet through the two-dimensional coupling grating module, the separation and conversion of the polarization directions which are orthogonal to each other are realized, and two output beams of light, namely an X polarization signal and a Y polarization signal, are both in a TE0 mode in the silicon single-mode waveguide; the local oscillation light is coupled to the chip through the one-dimensional coupling grating to become a TE0 mode in the silicon single-mode waveguide; the 1 x 2MMI beam splitter module is connected with the one-dimensional coupling grating to realize the uniform beam splitting of the local oscillator light 50:50 and respectively combine the local oscillator light with the signal light beam I and the signal light beam II; two input ports of the 2x 2MMI interferometer module are respectively connected with the 1 x 2MMI beam splitter module and the two-dimensional coupling grating module, so that the first signal beam and the local oscillator light, and the second signal beam and the local oscillator light are respectively combined; and finally, the two single-ended light detector modules are respectively connected with the two beams of combined beams of light, output current signals, namely the electric signal of the X single-polarization signal and the electric signal of the Y single-polarization signal, are detected according to the square rate, and are collected to enter a digital signal processing stage. It should be noted that each 2 × 2MMI interferometer has two wide output ports, and these two ports have equivalent functions, and only one of the outputs needs to be used.
The above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the same, and a person skilled in the art can modify the technical solution of the present invention or substitute the same without departing from the spirit and scope of the present invention, and the scope of the present invention should be determined by the claims.

Claims (9)

1.一种偏振分集的光外差相干接收方法，其步骤包括：1. A method for optical heterodyne coherent reception of polarization diversity, the steps comprising: 1)对偏振复用信号光进行分束，得到X单偏振信号和Y单偏振信号；对本振光进行分束，得到两束本振光；其中生成所述偏振复用信号光的方法为：将信号光分成两路并分别调制X偏振信号和Y偏振信号；然后对X偏振信号和Y偏振信号分别依次进行二进制序列到星座图符号的映射、加入帧前导序列以及奈奎斯特成型滤波后进行合束，形成所述偏振复用信号光；1) splitting the polarization multiplexing signal light to obtain X single polarization signal and Y single polarization signal; splitting the local oscillator light to obtain two beams of local oscillator light; wherein the method for generating the polarization multiplexing signal light is: Divide the signal light into two paths and modulate the X-polarized signal and the Y-polarized signal respectively; then perform the mapping of the binary sequence to the constellation symbol, add the frame preamble sequence and Nyquist shaping filter for the X-polarized signal and the Y-polarized signal respectively. performing beam combining to form the polarization multiplexed signal light; 2)将一束本振光与X单偏振信号保持相同偏振方向通过光耦合器进行合束并对合束后的信号进行功率检测，将另一束本振光与Y单偏振信号保持相同偏振方向通过光耦合器进行合束并对合束后的信号进行功率检测，得到X单偏振信号的电信号和Y单偏振信号的电信号；2) Keep a beam of local oscillator light and the X single-polarization signal in the same polarization direction, combine the beams through an optical coupler, and perform power detection on the combined signal, and keep another beam of local oscillator light and the Y single-polarization signal in the same polarization direction. The direction is combined by the optical coupler and the power detection of the combined signal is performed to obtain the electrical signal of the X single-polarization signal and the electrical signal of the Y single-polarization signal; 3)对两路功率检测得到的X单偏振信号的电信号和Y单偏振信号的电信号依次进行信号-信号拍频干扰补偿、下变频、奈奎斯特匹配滤波；然后对滤波后的两路信号联合均衡，得到解调信号。3) Perform signal-signal beat interference compensation, down-conversion, and Nyquist matching filtering on the electrical signal of the X single-polarization signal and the electrical signal of the Y single-polarization signal obtained by the two-way power detection in turn; The signals are jointly equalized to obtain a demodulated signal. 2.如权利要求1所述的方法，其特征在于，分别对奈奎斯特成型滤波后的信号进行色散预补偿Spre(f)＝S(f)·exp(-β2Lω2/2)，然后进行合束；其中，Spre(f)是预补偿之后的频域数据，S(f)是预补偿前的频域数据，β2为群速度色散系数，L为通信信道中的光纤长度，ω为信号频域上各频点相对于本振光的角频率。2 . The method according to claim 1 , wherein dispersion pre-compensation S pre (f)=S(f)·exp(-β 2 Lω 2 /2 is performed on the Nyquist shaping filtered signals respectively. 3 . ), and then combine beams; wherein, S pre (f) is the frequency domain data after pre-compensation, S(f) is the frequency domain data before pre-compensation, β 2 is the group velocity dispersion coefficient, and L is the communication channel. Fiber length, ω is the angular frequency of each frequency point in the signal frequency domain relative to the local oscillator light. 3.如权利要求1所述的方法，其特征在于，所述奈奎斯特成型滤波为滚降系数为α的奈奎斯特滤波；α取值为0.01。3 . The method according to claim 1 , wherein the Nyquist shaping filter is a Nyquist filter with a roll-off coefficient of α; and the value of α is 0.01. 4 . 4.如权利要求1所述的方法，其特征在于，步骤3)中，利用
Figure FDA0002331094760000011
进行信号-信号拍频干扰补偿；其中，i＝1、2，
Figure FDA0002331094760000012
为干扰补偿后的信号，ri(t)表示接收到的本振光和信号光拍频信号，λ是幅度因子。4. method as claimed in claim 1 is characterized in that, in step 3), utilize
Figure FDA0002331094760000011
Perform signal-signal beat interference compensation; where, i=1, 2,
Figure FDA0002331094760000012
For the signal after interference compensation, ri (t) represents the received beat frequency signal of the local oscillator light and signal light, and λ is the amplitude factor. 5.如权利要求1～4任一所述的方法，其特征在于，利用二维耦合光栅将偏振复用信号光耦合到片上并对偏振复用信号光进行分束；利用一维耦合光栅将本振光耦合到片上，然后利用一1×2多模干涉分束器对本振光进行分束；利用一2×2MMI干涉器对一束本振光与X单偏振信号进行合束，利用另一2×2MMI干涉器对另一束本振光与Y单偏振信号进行合束。5. The method according to any one of claims 1 to 4, wherein a two-dimensional coupling grating is used to couple the polarization multiplexed signal light to the chip and split the polarization multiplexed signal light; The local oscillator light is coupled to the chip, and then a 1 × 2 multi-mode interference beam splitter is used to split the local oscillator light; a 2 × 2 MMI interferometer is used to combine a beam of local oscillator light and X single-polarized signal, and use another A 2×2 MMI interferometer combines the other local oscillator light with the Y single-polarized signal. 6.如权利要求1～4任一所述的方法，其特征在于，利用偏振分束器对偏振复用信号光进行分束；利用光分束器对本振光进行分束；利用一光合束器对一束本振光与X单偏振信号进行合束，利用另一光合束器对另一束本振光与Y单偏振信号进行合束。6. The method according to any one of claims 1 to 4, wherein the polarization multiplexed signal light is split by a polarization beam splitter; the local oscillator light is split by an optical beam splitter; The device combines a beam of local oscillator light and X single-polarized signal, and uses another optical beam combiner to combine another beam of local oscillator light and Y single-polarized signal. 7.一种偏振分集的光外差相干接收系统，包括一接收端，其特征在于，所述接收端包括：7. A polarization diversity optical heterodyne coherent receiving system, comprising a receiving end, wherein the receiving end comprises: 偏振分集外差接收机模块，用于对偏振复用信号光进行分束，得到X单偏振信号和Y单偏振信号；对本振光进行分束，得到两束本振光；然后将一束本振光与X单偏振信号保持相同偏振方向通过光耦合器进行合束并对合束后的信号进行功率检测得到X单偏振信号的电信号，将另一束本振光与Y单偏振信号保持相同偏振方向通过光耦合器进行合束并对合束后的信号进行功率检测得到Y单偏振信号的电信号；其中生成所述偏振复用信号光的方法为：将信号光分成两路并分别调制X偏振信号和Y偏振信号；然后对X偏振信号和Y偏振信号分别依次进行二进制序列到星座图符号的映射、加入帧前导序列以及奈奎斯特成型滤波后进行合束，形成所述偏振复用信号光；The polarization diversity heterodyne receiver module is used to split the polarization multiplexed signal light to obtain X single polarization signal and Y single polarization signal; split the local oscillator light to obtain two beams of local oscillator light; The vibrating light and the X single-polarization signal keep the same polarization direction, and the optical coupler is used for beam combining and the power detection of the combined signal is performed to obtain the electrical signal of the X single-polarization signal, and the other beam of local oscillator light and the Y single-polarization signal are maintained. The same polarization direction is combined by an optical coupler and the power of the combined signal is detected to obtain an electrical signal of a Y single-polarized signal; wherein the method for generating the polarization multiplexed signal light is: dividing the signal light into two paths and separately Modulate the X-polarized signal and the Y-polarized signal; then perform the mapping of the binary sequence to the constellation symbol, add the frame preamble sequence and the Nyquist shaping filter on the X-polarized signal and the Y-polarized signal respectively, and then combine the beams to form the polarization multiplexed signal light; 信号-信号拍频干扰补偿模块，连接偏振分集外差接收机模块，用于分别对X单偏振信号的电信号和Y单偏振信号的电信号补偿信号-信号拍频干扰；The signal-signal beat frequency interference compensation module is connected to the polarization diversity heterodyne receiver module, and is used to compensate the signal-signal beat frequency interference for the electrical signal of the X single-polarization signal and the electrical signal of the Y single-polarization signal respectively; 下变频模块，连接信号-信号拍频干扰补偿模块，用于将信号-信号拍频干扰补偿模块输出的电信号分别变频为基带信号；The down-conversion module is connected to the signal-signal beat frequency interference compensation module, and is used for frequency-converting the electrical signals output by the signal-signal beat frequency interference compensation module into baseband signals respectively; 奈奎斯特滤波模块，连接下变频模块，用于分别消除下变频模块输出的基带信号中的码间串扰；The Nyquist filter module is connected to the down-conversion module, and is used to respectively eliminate the inter-symbol crosstalk in the baseband signal output by the down-conversion module; 联合均衡模块，用于同时均衡两个滤波后的电信号，然后输出解调信号。The joint equalization module is used to equalize the two filtered electrical signals at the same time, and then output the demodulated signal. 8.如权利要求7所述的系统，其特征在于，所述偏振分集外差接收机模块包括：8. The system of claim 7, wherein the polarization diversity heterodyne receiver module comprises: 偏振分束模块，用于对偏振复用信号光进行偏振分束，得到X单偏振信号和Y单偏振信号；The polarization beam splitting module is used for polarization beam splitting of polarization multiplexed signal light to obtain X single polarization signal and Y single polarization signal; 光分束器模块，用于对本振光进行分束，得到两束本振光；The optical beam splitter module is used to split the local oscillator light to obtain two local oscillator light beams; 第一光合束器模块，连接偏振分束模块以及光分束器模块，用于将一束本振光与X单偏振信号保持相同偏振方向通过光耦合器进行合束；The first optical beam combiner module is connected to the polarization beam splitter module and the optical beam splitter module, and is used to combine a beam of local oscillator light and the X single-polarized signal in the same polarization direction through an optical coupler; 第二光合束器模块，连接偏振分束模块以及光分束器模块，用于另一束本振光与Y单偏振信号保持相同偏振方向通过光耦合器进行合束；The second optical beam combiner module is connected to the polarization beam splitter module and the optical beam splitter module, and is used for another beam of local oscillator light and the Y single-polarized signal to maintain the same polarization direction through the optical coupler for beam combining; 第一单端光探测器模块，与第一光合束器模块连接，用于检测合束后的光功率；a first single-ended optical detector module, connected to the first optical beam combiner module, for detecting the combined optical power; 第二单端光探测器模块，与第二光合束器模块连接，用于检测合束后的光功率。The second single-ended optical detector module is connected to the second optical beam combiner module, and is used for detecting the optical power after the beam combination. 9.如权利要求8所述的系统，其特征在于，所述偏振分束模块为二维耦合光栅；所述本振光通过一维耦合光栅耦合到片上，所述光分束器模块为一1×2多模干涉分束器，与该一维耦合光栅连接；所述第一光合束器模块、第二光合束器模块分别为一2×2MMI干涉器。9. The system according to claim 8, wherein the polarization beam splitting module is a two-dimensional coupling grating; the local oscillator light is coupled to the chip through a one-dimensional coupling grating, and the optical beam splitter module is a one-dimensional coupling grating. A 1×2 multi-mode interference beam splitter is connected to the one-dimensional coupling grating; the first optical beam combiner module and the second optical beam combiner module are respectively a 2×2 MMI interferometer.
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