Clock recovery system and method for multi-aperture coherent optical signal

Abstract

The invention relates to the technical field of optical fiber communication, and discloses a clock recovery system and method for a multi-aperture coherent optical signal, and the system comprises an interpolator which obtains coherent optical signals received through a plurality of different apertures, and carries out the preliminary adjustment of the clock phase of the coherent optical signals; the MIMO equalizer equalizes and synthesizes a plurality of coherent optical signals of which the clock phases are readjusted, and the error detector tracks the clock phases of the transmitted coherent optical signals in real time and extracts the clock phase error of each coherent optical signal relative to the transmitted coherent optical signals in the synthesized coherent optical signals. The clock generation chip is used for generating a reference clock with a corresponding clock phase according to the clock phase error of each coherent optical signal, so that the clock phase of each coherent optical signal is readjusted through the reference clock, and at the moment, the coherent optical signals with the readjusted clock phases are balanced and synthesized; the quality of the synthesized multi-aperture signal can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communication, and in particular to a clock recovery system and method for multi-aperture coherent optical signals. Background Art

[0002] Multi-aperture diversity reception technology is a technology used to improve receiver performance. It is particularly suitable for ground optical stations in satellite-to-ground laser communication systems to process weak optical signals. This technology can significantly increase the received optical power of the downlink. Among them, multiple apertures can effectively increase the total collection area, alleviate the impact of wavefront phase distortion caused by atmospheric turbulence, and significantly alleviate the deep fading experienced by a single aperture. The optical signal received by a single aperture branch is usually very weak, and the received signal will suffer from time-related power fading, resulting in a decrease in the performance of clock extraction and tracking of the single aperture branch signal. The clock recovery algorithm can be used to recover the clock of the optical signal received by each aperture branch.

[0003] However, the current clock recovery algorithm estimates and compensates for clock deviations for different aperture branches respectively. In the synthesis of multi-aperture coherent optical signals, when one of the signals is in a long-term deep fade, the clock of this branch will be unlocked. After losing the lock, the sampling clock will deviate, resulting in the signal after the unlocking is combined with the signal power of other branches, which will seriously reduce the quality of the synthesized signal. Summary of the invention

[0004] The object of the present invention is to provide a clock recovery system and method for a multi-aperture coherent optical signal, which can improve the quality of the synthesized multi-aperture coherent optical signal.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a clock recovery system for a multi-aperture coherent optical signal, comprising:

[0006] A plurality of interpolators, each of which is used to obtain coherent optical signals received through a plurality of different apertures, and respectively perform preliminary adjustment on the clock phase of the received coherent optical signals to synchronize the clock phase of the received coherent optical signals with the clock phase of the transmitted coherent optical signals;

[0007] A MIMO equalizer is used to equalize the coherent optical signals after the preliminary adjustment of the clock phases to eliminate the channel interference in the coherent optical signals after the preliminary adjustment of the clock phases, and synthesize the equalized coherent optical signals to obtain a synthesized coherent optical signal;

[0008] an error detector, for tracking the clock phase of the transmitted coherent optical signal in real time, and extracting the clock phase error of each coherent optical signal in the synthesized coherent optical signal relative to the transmitted coherent optical signal;

[0009] A clock generation chip, used for generating a reference clock with a corresponding clock phase according to a clock phase error of each coherent optical signal, so as to readjust the clock phase of each coherent optical signal through the reference clock;

[0010] The MIMO equalizer is also used to equalize multiple coherent optical signals after the clock phases are readjusted to eliminate channel interference in the multiple coherent optical signals after the clock phases are readjusted, and synthesize the multiple equalized coherent optical signals to obtain a target synthesized coherent optical signal.

[0011] In some optional embodiments, the plurality of interpolators are further used to adjust the interpolation phase of the interpolator according to the clock phase error of each coherent optical signal, and readjust the clock phase of the corresponding coherent optical signal according to the adjusted interpolation phase;

[0012] The MIMO equalizer is specifically used to equalize and synthesize coherent optical signals after multiple clock phases are readjusted through a reference clock, or to equalize and synthesize coherent optical signals after multiple clock phases are readjusted through multiple interpolators.

[0013] In some optional embodiments, the clock generation chip is a DDS chip.

[0014] In some optional embodiments, the coherent optical signal received by each of the apertures includes four branch coherent optical signals, each branch coherent optical signal corresponds to an interpolator, and each interpolator is used to preliminarily adjust the clock phase of the corresponding branch coherent optical signal, and readjust the clock phase of the corresponding branch coherent optical signal according to the clock phase error.

[0015] In some optional embodiments, if the MIMO equalizer is used to equalize and synthesize coherent optical signals after multiple clock phases are readjusted through multiple interpolators, the MIMO equalizer is a frequency domain MIMO equalizer or a time domain MIMO equalizer.

[0016] In some optional embodiments, the MIMO equalizer is a 2N×2 frequency domain MIMO equalizer, a 2N×2 time domain MIMO equalizer, a 4N×2 frequency domain MIMO equalizer, a 4N×2 time domain MIMO equalizer, a 4N×4 frequency domain MIMO equalizer or a 4N×4 time domain MIMO equalizer.

[0017] In some optional embodiments, the system further includes a frequency offset compensation module, wherein the frequency offset compensation module is used to estimate a dynamic frequency offset between multiple coherent optical signals through a target synthetic coherent optical signal, and compensate for the dynamic frequency offset.

[0018] In some optional embodiments, the system further includes a QAM demapping module, and the QAM demapping module is used to convert the target synthetic coherent optical signal after dynamic frequency offset compensation into a binary bit stream.

[0019] An embodiment of the present invention further provides a method for a clock recovery system based on the multi-aperture coherent optical signal, comprising:

[0020] Acquire coherent optical signals received through a plurality of different apertures, and preliminarily adjust the clock phases of the received coherent optical signals respectively to synchronize the clock phases of the received coherent optical signals with the clock phases of the transmitted coherent optical signals;

[0021] Equalizing a plurality of coherent optical signals after the initial adjustment of the clock phases to eliminate channel interference in the plurality of coherent optical signals after the initial adjustment of the clock phases, and synthesizing the equalized plurality of coherent optical signals to obtain a synthesized coherent optical signal;

[0022] Tracking the clock phase of the transmitted coherent optical signal in real time, and extracting the clock phase error of each coherent optical signal in the synthesized coherent optical signal relative to the transmitted coherent optical signal;

[0023] According to the clock phase error of each coherent optical signal, a reference clock having a corresponding clock phase is generated to readjust the clock phase of each coherent optical signal through the reference clock;

[0024] The multiple coherent optical signals after the clock phases are readjusted are equalized to eliminate channel interference in the multiple coherent optical signals after the clock phases are readjusted, and the multiple coherent optical signals after the equalization are synthesized to obtain a target synthesized coherent optical signal.

[0025] The clock recovery system for multi-aperture coherent optical signals provided by the present invention has at least the following beneficial effects:

[0026] For coherent optical signals from multiple different apertures, the clock phase of the coherent optical signal of each aperture is preliminarily adjusted through an interpolator. After the clock phase of the received coherent optical signal is synchronized with the clock phase of the transmitted coherent optical signal, a MIMO equalizer is used to equalize and synthesize multiple coherent optical signals after the clock phase is preliminarily adjusted. Due to environmental factors (such as temperature, pressure, etc.), the clock phase of the transmitted coherent optical signal is constantly changing. At this time, the clock phases of the multiple coherent optical signals are re-adjusted based on the clock phase errors between the multiple coherent optical signals in the coherent optical signal after equalization and synthesis. Finally, the MIMO equalizer synthesizes the multiple coherent optical signals after the clock phase is re-adjusted. In the present invention, the multi-path coherent optical signals input to the MIMO equalizer are coherent optical signals for clock recovery, and clock recovery is performed again according to the signal feedback output by the MIMO equalizer, thereby realizing the joint processing of clock recovery of multiple coherent optical signals and MIMO equalization. The joint processing can improve the clock tracking performance of the coherent optical signals received by multiple apertures to the coherent optical signals transmitted, thereby improving the quality and synthesis efficiency of the synthesized coherent optical signals synthesized by MIMO equalization. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] One or more embodiments are exemplarily described by the pictures in the corresponding drawings, and these exemplary descriptions do not constitute limitations on the embodiments.

[0028] Figure 1 FIG. 1 is a schematic diagram of the architecture of a clock recovery system for a multi-aperture coherent optical signal provided according to an embodiment of the present invention. Figure 1 ;

[0029] Figure 2 FIG. 1 is a schematic diagram of the architecture of a clock recovery system for a multi-aperture coherent optical signal provided according to an embodiment of the present invention. Figure 2 ;

[0030] Figure 3 is a schematic diagram of an architecture of (i) coherent optical signal clock recovery according to an embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of an architecture for clock recovery of a (ii)-path coherent optical signal provided according to an embodiment of the present invention;

[0032] Figure 5 The present invention is a flowchart of a method for a clock recovery system based on a multi-aperture coherent optical signal provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in the embodiments of the present invention, many technical details are proposed in order to enable the reader to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present invention can be implemented. The division of the following embodiments is for the convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other without contradiction.

[0034] An embodiment of the present invention relates to a clock recovery system for a multi-aperture coherent optical signal. The implementation details of the clock recovery system for a multi-aperture coherent optical signal of this embodiment are described in detail below. The following content is only the implementation details provided for the convenience of understanding and is not necessary for the implementation of this solution.

[0035] The specific architecture of the clock recovery system for multi-aperture coherent optical signals of this embodiment can be as follows: Figure 1 As shown, it includes: multiple interpolators, MIMO equalizers, error detectors and clock generation chips.

[0036] Multiple interpolators are used to obtain coherent optical signals received through multiple different apertures, and respectively make preliminary adjustments to the clock phases of the received coherent optical signals to synchronize the clock phases of the received coherent optical signals with the clock phases of the transmitted coherent optical signals. The coherent optical signals received by each aperture contain four branch coherent optical signals. Therefore, each branch coherent optical signal actually corresponds to an interpolator, and each interpolator is used to make preliminary adjustments to the clock phase of the corresponding branch coherent optical signal, and to readjust the clock phase of the corresponding branch coherent optical signal according to the clock phase error. Therefore, Figure 1 Interpolator 1, interpolator 2, interpolator 3 and interpolator 4 shown in the figure actually represent multiple interpolators corresponding to aperture 1, aperture 2, aperture 3 and aperture 4 respectively.

[0037] The MIMO equalizer is used to equalize multiple coherent optical signals after the initial adjustment of the clock phases, so as to eliminate the channel interference in the coherent optical signals after the initial adjustment of the clock phases, and synthesize the multiple equalized coherent optical signals to obtain a synthesized coherent optical signal.

[0038] The error detector is used to track the clock phase of the transmitted coherent optical signal in real time and extract the clock phase error of each coherent optical signal in the composite coherent optical signal relative to the transmitted coherent optical signal. Due to environmental factors (such as temperature, pressure, etc.), the clock phase of the coherent optical signal transmitted by the transmitter is constantly changing. Therefore, the error detector is designed in this embodiment, which can detect the clock phase error of the received coherent optical signal relative to the transmitted coherent optical signal in real time.

[0039] At this time, it is necessary to readjust the clock phase of each coherent optical signal according to the real-time detection of the clock phase error of the received coherent optical signal relative to the transmitted coherent optical signal, which can be achieved through a clock generation chip: the clock generation chip is used to generate a reference clock with a corresponding clock phase according to the clock phase error of each coherent optical signal, so as to readjust the clock phase of each coherent optical signal through the reference clock. At this time, the MIMO equalizer is also used to equalize multiple coherent optical signals after the clock phases are readjusted, so as to eliminate the channel interference in the multiple coherent optical signals after the clock phases are readjusted, and synthesize the multiple coherent optical signals after equalization to obtain the target synthesized coherent optical signal. Among them, the clock generation chip is specifically a DDS chip.

[0040] There is another way to readjust the clock phase of each coherent optical signal according to the real-time detection of the clock phase error of the received coherent optical signal relative to the transmitted coherent optical signal, which is achieved through multiple interpolators: the multiple interpolators are also used to adjust the interpolation phase of the interpolator according to the clock phase error of each coherent optical signal, and readjust the clock phase of the corresponding coherent optical signal according to the adjusted interpolation phase. In this case, the MIMO equalizer is specifically used to equalize and synthesize the coherent optical signals after multiple clock phases are readjusted through the reference clock, or to equalize and synthesize the coherent optical signals after multiple clock phases are readjusted through multiple interpolators.

[0041] In one example, if the MIMO equalizer is used to equalize and synthesize coherent optical signals after multiple clock phases are readjusted by multiple interpolators, the MIMO equalizer is specifically a frequency domain MIMO equalizer or a time domain MIMO equalizer to reduce power consumption of the system.

[0042] The MIMO equalizer may specifically be a 2N×2 frequency domain MIMO equalizer, a 2N×2 time domain MIMO equalizer, a 4N×2 frequency domain MIMO equalizer, a 4N×2 time domain MIMO equalizer, a 4N×4 frequency domain MIMO equalizer or a 4N×4 time domain MIMO equalizer.

[0043] In this embodiment, for coherent optical signals from multiple different apertures, the clock phase of the coherent optical signal of each aperture is preliminarily adjusted by an interpolator, and after the clock phase of the received coherent optical signal is synchronized with the clock phase of the transmitted coherent optical signal, a MIMO equalizer is used to equalize and synthesize multiple coherent optical signals after the clock phase is preliminarily adjusted. Due to environmental factors (such as temperature, pressure, etc.), the clock phase of the transmitted coherent optical signal is constantly changing. At this time, the clock phases of the multiple coherent optical signals are re-adjusted based on the clock phase errors between the multiple coherent optical signals in the coherent optical signal after equalization and synthesis. Finally, the MIMO equalizer synthesizes the multiple coherent optical signals after the clock phase is re-adjusted. In this embodiment, the multi-path coherent optical signals input to the MIMO equalizer are coherent optical signals for clock recovery, and clock recovery is performed again according to the signal feedback output by the MIMO equalizer, thereby realizing the joint processing of clock recovery of multiple coherent optical signals and MIMO equalization. The joint processing can improve the clock tracking performance of the coherent optical signals received by multiple apertures to the transmitted coherent optical signals, thereby improving the quality and synthesis efficiency of the synthesized coherent optical signal synthesized by MIMO equalization.

[0044] In one embodiment, the specific architecture of the clock recovery system for multi-aperture coherent optical signals of the present invention is as follows: Figure 2 As shown in the figure, this architecture details how to achieve clock recovery of coherent optical signals received by multiple different apertures to improve the quality of the synthesized signal:

[0045] First, multiple different apertures are used to receive spatial optical signals, that is, the signals after wavefront distortion in the figure. The coherent optical signals corresponding to each aperture are amplified by their corresponding erbium doped fiber amplifiers (EDFA) and sent to the integrated coherent receiver (ICR). After the ICR, the signals sampled by the analog-to-digital converter (ADC) are sent to the orthogonal I / Q imbalance compensation module for XX, and then sent to the interpolator to adjust the clock phase of the coherent optical signal. After the multi-channel coherent optical signals are sent to the MIMO equalizer, the multi-channel coherent optical signals are equalized and synthesized. The equalized and synthesized signals will also be processed by subsequent DSP algorithms, including frequency deviation, phase deviation estimation and compensation, QAM demapping, etc.

[0046] After the MIMO equalizer realizes the equalization and synthesis of multiple coherent optical signals, the clock phase error between the multiple coherent optical signals can be extracted by the error detector, and then the clock phase of the multiple coherent optical signals can be readjusted based on the clock phase error to accurately realize the clock recovery of the multiple coherent optical signals. There are two ways to realize the readjustment of the clock phase of the multiple coherent optical signals, namely Figure 2In (i) and (ii), path (i) is to use multiple interpolators to readjust the clock phase of the coherent optical signal received by the corresponding integrated coherent receiver through the clock phase error, and path (ii) is to generate a reference clock of corresponding frequency and phase according to the clock error to readjust the clock phase of the coherent optical signal received by the corresponding integrated coherent receiver through the reference clock, and the clock phase adjusted by the reference clock of path (ii) is the clock phase of the coherent optical signal sampled by the ADC.

[0047] Figure 3 and Figure 4 The specific architectures of the clock recovery of the coherent optical signal in paths (i) and (ii) are shown respectively: Figure 3 In the process, the signal processed by the interpolator is sent to the MIMO equalizer, and the signal after equalization and synthesis by the MIMO equalizer is sent to the error detector. Then, the control signal sent to the interpolator is processed by loop filtering, numerically controlled oscillators and controllers to better control the interpolator to readjust the clock phase of the coherent optical signal. Figure 4 In the process, the signal processed by the interpolator is sent to the MIMO equalizer, and the signal after equalization and synthesis by the MIMO equalizer is sent to the error detector. The control signal sent to the DDS chip is then processed by loop filtering, digitally controlled oscillators and controllers, so that the DDS chip can better control the clock generation chip to generate a reference clock of corresponding frequency and phase, and readjust the clock phase of the coherent optical signal. A low-pass filter is also set between the DDS chip and the clock generation chip to filter the control signal from the DDS chip to the clock generation chip.

[0048] Another embodiment of the present invention relates to a method for a clock recovery system based on a multi-aperture coherent optical signal. The implementation details of the method for a clock recovery system based on a multi-aperture coherent optical signal of this embodiment are described in detail below. The following content is only for the convenience of understanding the implementation details provided, and is not necessary for the implementation of this solution. The flowchart of the method for a clock recovery system based on a multi-aperture coherent optical signal of this embodiment can be as follows: Figure 5 As shown, including:

[0049] Step 501: acquiring coherent optical signals received through a plurality of different apertures, and preliminarily adjusting the clock phases of the received coherent optical signals respectively, so as to synchronize the clock phases of the received coherent optical signals with the clock phases of the transmitted coherent optical signals.

[0050] Step 502: Equalize a plurality of coherent optical signals after the initial adjustment of the clock phases to eliminate channel interference in the plurality of coherent optical signals after the initial adjustment of the clock phases, and synthesize the plurality of equalized coherent optical signals to obtain a synthesized coherent optical signal.

[0051] Step 503: Track the clock phase of the transmitted coherent optical signal in real time, and extract the clock phase error of each coherent optical signal in the synthesized coherent optical signal relative to the transmitted coherent optical signal.

[0052] Step 504: Generate a reference clock with a corresponding clock phase according to the clock phase error of each coherent optical signal, so as to readjust the clock phase of each coherent optical signal through the reference clock.

[0053] Step 505 , equalize the multiple coherent optical signals after the clock phases are readjusted to eliminate channel interference in the multiple coherent optical signals after the clock phases are readjusted, and synthesize the multiple equalized coherent optical signals to obtain a target synthesized coherent optical signal.

[0054] The steps of the above methods are divided only for clear description. When implemented, they can be combined into one step or some steps can be split and decomposed into multiple steps. As long as they include the same logical relationship, they are all within the protection scope of the present invention.

[0055] It is not difficult to find that this embodiment is a method embodiment corresponding to the above system embodiment, and this embodiment can be implemented in conjunction with the above method embodiment. The relevant technical details and technical effects mentioned in the above embodiment are still valid in this embodiment, and in order to reduce repetition, they are not repeated here. Accordingly, the relevant technical details mentioned in this embodiment can also be applied in the above embodiment.

[0056] Those skilled in the art can understand that the above embodiments are specific embodiments of the present invention, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of the embodiments of the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of the present invention, so the protection scope of the embodiments of the present invention shall be based on the scope defined in the claims.

Claims

1. A clock recovery system for multi-aperture coherent optical signals, characterized in that: include: A plurality of interpolators, each of which is used to obtain coherent optical signals received through a plurality of different apertures, and respectively perform preliminary adjustment on the clock phase of the received coherent optical signals to synchronize the clock phase of the received coherent optical signals with the clock phase of the transmitted coherent optical signals; A MIMO equalizer is used to equalize the coherent optical signals after the preliminary adjustment of the clock phases to eliminate the channel interference in the coherent optical signals after the preliminary adjustment of the clock phases, and synthesize the equalized coherent optical signals to obtain a synthesized coherent optical signal; an error detector, for tracking the clock phase of the transmitted coherent optical signal in real time, and extracting the clock phase error of each coherent optical signal in the composite coherent optical signal relative to the transmitted coherent optical signal; A clock generation chip, used for generating a reference clock with a corresponding clock phase according to a clock phase error of each coherent optical signal, so as to readjust the clock phase of each coherent optical signal through the reference clock; The MIMO equalizer is also used to equalize multiple coherent optical signals after the clock phases are readjusted to eliminate channel interference in the multiple coherent optical signals after the clock phases are readjusted, and synthesize the multiple equalized coherent optical signals to obtain a target synthesized coherent optical signal.

2. The clock recovery system for multi-aperture coherent optical signals according to claim 1, characterized in that: The multiple interpolators are further used to adjust the interpolation phase of the interpolator according to the clock phase error of each coherent optical signal, and readjust the clock phase of the corresponding coherent optical signal according to the adjusted interpolation phase; The MIMO equalizer is specifically used to equalize and synthesize coherent optical signals after multiple clock phases are readjusted through a reference clock, or to equalize and synthesize coherent optical signals after multiple clock phases are readjusted through multiple interpolators.

3. The clock recovery system for multi-aperture coherent optical signals according to claim 1, characterized in that: The clock generation chip is a DDS chip.

4. The clock recovery system for multi-aperture coherent optical signals according to claim 2, characterized in that: The coherent optical signal received by each aperture includes four branch coherent optical signals, each branch coherent optical signal corresponds to an interpolator, and each interpolator is used to preliminarily adjust the clock phase of the corresponding branch coherent optical signal and readjust the clock phase of the corresponding branch coherent optical signal according to the clock phase error.

5. The clock recovery system for multi-aperture coherent optical signals according to claim 2, characterized in that: If the MIMO equalizer is used to equalize and synthesize coherent optical signals after multiple clock phases are readjusted through multiple interpolators, the MIMO equalizer is a frequency domain MIMO equalizer or a time domain MIMO equalizer.

6. The clock recovery system for multi-aperture coherent optical signals according to claim 5, characterized in that: The MIMO equalizer is a 2N×2 frequency domain MIMO equalizer, a 2N×2 time domain MIMO equalizer, a 4N×2 frequency domain MIMO equalizer, a 4N×2 time domain MIMO equalizer, a 4N×4 frequency domain MIMO equalizer or a 4N×4 time domain MIMO equalizer.

7. The clock recovery system for multi-aperture coherent optical signals according to claim 1, characterized in that: The system further comprises a frequency offset compensation module, which is used to estimate the dynamic frequency offset between the plurality of coherent optical signals through the target synthetic coherent optical signal and compensate for the dynamic frequency offset.

8. The clock recovery system for multi-aperture coherent optical signals according to claim 7, characterized in that: The system further comprises a QAM demapping module, which is used for converting the target synthetic coherent optical signal after dynamic frequency offset compensation into a binary bit stream.

9. A method for a clock recovery system of a multi-aperture coherent optical signal based on any one of claims 1 to 8, characterized in that: include: Acquire coherent optical signals received through a plurality of different apertures, and preliminarily adjust the clock phases of the received coherent optical signals respectively to synchronize the clock phases of the received coherent optical signals with the clock phases of the transmitted coherent optical signals; Equalizing a plurality of coherent optical signals after the initial adjustment of the clock phases to eliminate channel interference in the plurality of coherent optical signals after the initial adjustment of the clock phases, and synthesizing the equalized plurality of coherent optical signals to obtain a synthesized coherent optical signal; Tracking the clock phase of the transmitted coherent optical signal in real time, and extracting the clock phase error of each coherent optical signal in the synthesized coherent optical signal relative to the transmitted coherent optical signal; According to the clock phase error of each coherent optical signal, a reference clock having a corresponding clock phase is generated to readjust the clock phase of each coherent optical signal through the reference clock; The multiple coherent optical signals after the clock phases are readjusted are equalized to eliminate channel interference in the multiple coherent optical signals after the clock phases are readjusted, and the multiple coherent optical signals after the equalization are synthesized to obtain a target synthesized coherent optical signal.

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