CN115529086A

CN115529086A - Coherent receiving device, coherent receiving method and coherent communication system

Info

Publication number: CN115529086A
Application number: CN202110713291.9A
Authority: CN
Inventors: 杨婷; 于瀛; 陈杰
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2022-12-27
Also published as: WO2022267546A1

Abstract

The application discloses a coherent receiving device, a coherent receiving method and a coherent communication system, which are applied to the field of optical communication. The coherent receiving device comprises a polarization beam splitting and rotating module, a phase shifter, a coupler, a laser and a mixer. The polarization beam splitting and rotating module is used for receiving the signal light and splitting the signal light into first signal light and second signal light, and the first signal light and the second signal light have the same polarization state. And the phase shifter is used for shifting the phase of the first signal light to obtain the phase-shifted first signal light, and the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference. And the coupler is used for combining the first signal light and the second signal light after phase shifting to obtain combined signal light. And the laser is used for sending the generated local oscillation light to the frequency mixer, and the local oscillation light and the combined signal light have the same polarization state. And the mixer is used for optically mixing the combined signal light and the local oscillator light to obtain the mixed signal light.

Description

Coherent receiving device, coherent receiving method and coherent communication system

Technical Field

The present application relates to the field of optical communications, and in particular, to a coherent receiving apparatus, a coherent receiving method, and a coherent communication system.

Background

With the ever-increasing demand for network capacity, ethernet data rates are evolving and evolving at a dramatic rate, and coherent detection techniques can exploit multiple degrees of freedom of light including polarization, intensity, and phase to carry information, and thus can improve spectral efficiency. In addition, the coherent detection has high receiving sensitivity, and benefits from the strong Digital Signal Processing (DSP) capability in the coherent detection technology, and can compensate the optical fiber dispersion, so the coherent detection technology is widely applied to long-distance high-speed optical transmission systems. In order to keep up with the enormous pace of data growth, and to cope with the demand for capacity acceleration, it is a necessary trend that coherent detection technology sinks to short-distance transmission scenarios such as data centers, access networks, and the like. In these application scenarios, the cost, size, and power consumption of the optical module are sensitive. In addition, in the future huge medium and short distance metropolitan market, there is also a cost reduction space, and a low-cost and simplified coherent solution is urgently needed to be found.

At present, in order to reduce the size and power consumption of the coherent optical module, a single-polarization coherent system can be used to reduce the number of optical and electronic components involved, for example, one path of modulator is used on the transmitting side to generate a single-polarization high-order modulation signal, and the number of modulators on the transmitting side is halved, thereby achieving the purpose of reducing the cost, size and power consumption of the coherent optical module. However, only halving the optical and electronic components on the receiving side may result in a situation where only part of the signal light is received or no signal light is received at all, and thus a coherent receiver still needs to employ a polarization diversity front end to be able to receive signals of both polarization components simultaneously, i.e., the optical and electronic components on the receiving side cannot be reduced, resulting in a limited reduction in cost, size and power consumption of the coherent optical module.

Disclosure of Invention

The application provides a coherent receiving device, a coherent receiving method and a coherent communication system, because a first signal light and a second signal light have the same polarization state, and a local oscillator light and a combined signal light have the same polarization state, the first signal light and the second signal light do not need to be processed respectively, thereby reducing the number of optical and electronic elements in a coherent optical module, and reducing the size and the power consumption of the coherent receiving device.

A first aspect of the present application provides a coherent receiving device, which includes a polarization beam splitting rotation module, a phase shifter, a coupler, a laser, and a mixer. Based on this, the polarization beam splitting and rotating module receives the signal light and splits the signal light into a first signal light and a second signal light, and the first signal light and the second signal light have the same polarization state. The phase shifter shifts the phase of the first signal light to obtain phase-shifted first signal light, and the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference. The coupler combines the phase-shifted first signal light and the phase-shifted second signal light to obtain combined signal light. The laser sends the generated local oscillation light to the frequency mixer, and the local oscillation light and the combined signal light have the same polarization state. The mixer optically mixes the combined signal light with the local oscillator light to obtain mixed signal light.

In this embodiment, the coherent receiving device performs phase shifting on the decomposed first signal light, so that the phase-shifted first signal light and the second signal light having the same polarization state keep a predetermined phase difference, and combines the phase-shifted first signal light and the second signal light having the same polarization state, that is, the first signal light and the second signal light do not need to be processed separately, thereby reducing the number of optical and electronic components in the coherent optical module, and being capable of reducing the size and power consumption of the coherent receiving device. Secondly, the combined signal light and the local oscillator light generated by the laser have the same polarization state, and the situation of polarization cancellation can be avoided.

In an alternative form of the first aspect, the polarization beam splitting rotation module is a polarization beam splitting rotator PSR.

In this embodiment, the polarization beam splitting and rotating module is a PSR that can directly perform polarization orthogonal decomposition on the signal light to obtain two paths of signal light with orthogonal polarization states, and the polarization state of one of the paths of signal light is fixedly rotated to align with the polarization state of the other path of signal light, so that the first signal light and the second signal light with the same polarization state are obtained, thereby improving the feasibility of the scheme.

In an alternative form of the first aspect, the polarization beam splitting rotation module comprises a polarization beam splitter PBS and a polarization rotator PR. Specifically, the PBS is configured to perform polarization orthogonal decomposition on the signal light to obtain a second signal light and a third signal light. And PR fixedly rotates the third signal light to obtain the first signal light.

In this embodiment, polarization orthogonal decomposition is performed through the PBS to obtain the second signal light and the third signal light, and the PR is used to rotate the third signal light to obtain the first signal light, so that another way of obtaining the first signal light and the second signal light is provided, thereby improving the flexibility of the scheme.

In an alternative form of the first aspect, the predetermined phase difference is 0 °, or 90 °.

In the embodiment, the preset phase differences in different application scenes are different, so that the flexibility of the scheme is improved.

In an alternative form of the first aspect, the coherent reception apparatus further comprises a balanced receiver, a transimpedance amplifier, and a first analog-to-digital converter. Based on this, the balanced receiver performs photoelectric conversion on the mixed signal light to obtain a photoelectric-converted analog electrical signal. And the trans-impedance amplifier adjusts the amplitude value of the analog electric signal after the photoelectric conversion so as to obtain the analog electric signal after the amplitude value is adjusted. The first analog-to-digital converter performs analog-to-digital conversion on the analog electric signal with the amplitude value adjusted to obtain a digital electric signal with the amplitude value adjusted.

In this embodiment, the balanced receiver, the transimpedance amplifier and the first analog-to-digital converter complete a subsequent processing procedure on the mixed signal light to obtain the digital electrical signal with the amplitude value adjusted, so as to support the digital signal processing module to perform data processing based on the digital electrical signal with the amplitude value adjusted, thereby improving the feasibility of the scheme.

In an optional manner of the first aspect, the coherent receiving apparatus further includes an optical-to-electrical conversion module and a feedback control module. Based on this, when the phase shifter shifts the phase of the first signal light, the phase shifter can also load the first pilot signal on the preset frequency point of the first signal light. The coupler splits the combined signal light into a fourth signal light and a fifth signal light. The photoelectric conversion module performs photoelectric conversion on the fifth signal light to obtain a first electric signal. The feedback control module calculates an estimated phase difference between the first signal light and the second signal light based on the first pilot signal, and determines a feedback control quantity according to the estimated phase difference and a preset phase difference. The feedback control module loads a feedback control quantity to the phase shifter. The phase shifter determines a phase value of the first signal light for phase shifting by the feedback control amount.

In this embodiment, the feedback control module calculates an estimated phase difference between the first signal light and the second signal light based on the first pilot signal, and loads a feedback control amount determined according to the estimated phase difference and a preset phase difference to the phase shifter, and the phase shifter can adjust a phase value of the phase shift of the first signal light in real time through the feedback control amount, so as to ensure that the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is the preset phase difference, and improve the reliability of the scheme.

In an optional manner of the first aspect, the feedback control module includes a second analog-to-digital converter, a first fourier transform module, a first microcontroller unit, and a first digital-to-analog converter. Based on this, the second analog-to-digital converter samples the first electric signal to obtain a sampled time domain digital signal, the first fourier transform module performs fourier transform on the sampled time domain digital signal to obtain a frequency domain digital signal, the first microcontroller unit extracts a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal from the frequency domain digital signal, the first microcontroller unit determines an estimated phase difference according to the first harmonic component of the first pilot signal and the second harmonic component of the first pilot signal, and determines a feedback control quantity according to the estimated phase difference and a preset phase difference. The first digital-to-analog converter converts the feedback control quantity into a direct-current voltage value, loads the direct-current voltage value to the phase shifter, and the phase shifter determines a phase value of the first signal light for phase shifting according to the direct-current voltage value.

In this embodiment, each module in the feedback control module determines an estimated phase difference between harmonic components of the first pilot signal, converts the feedback control quantity into a dc voltage value, and adjusts a phase value of the phase shift of the first signal light of the phase shifter in real time through the dc voltage value, so as to ensure that the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference, that is, ensure a superposition effect between the first signal light and the second signal light, avoid a situation of coherent cancellation, and further improve the reliability of the scheme.

In an optional manner of the first aspect, the first microcontroller unit is specifically configured to calculate a ratio of a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal to obtain the estimated phase difference.

In this embodiment, the estimated phase difference is specifically determined by the ratio between the harmonic components of the first pilot signal, thereby improving the feasibility of this scheme.

In an alternative form of the first aspect, the feedback control module includes a first low pass filter, a first multiplier, a first integrator, a second low pass filter, a second multiplier, a second integrator, a second microcontroller unit, and a second digital-to-analog converter. Based on this, the photoelectric conversion module divides the first electrical signal into a second electrical signal and a third electrical signal, the first low-pass filter performs low-pass filtering on the second electrical signal to obtain a low-pass filtered second electrical signal, and the first multiplier performs analog domain multiplication on the low-pass filtered second electrical signal and the first pilot signal to obtain a multiplied second electrical signal. The first integrator integrates the multiplied second electric signal to obtain an integrated second electric signal, the second low-pass filter low-pass filters the third electric signal to obtain a low-pass filtered third electric signal, the second multiplier multiplies the low-pass filtered third electric signal with the frequency doubling signal of the first pilot signal in an analog domain to obtain a multiplied third electric signal, and the second integrator integrates the multiplied third electric signal to obtain an integrated third electric signal. The second microcontroller unit determines an estimated phase difference according to the integrated second electric signal and the integrated third electric signal, determines a feedback control quantity according to the estimated phase difference and a preset phase difference, converts the feedback control quantity into a direct-current voltage value by the second digital-to-analog converter, loads the direct-current voltage value to the phase shifter, and determines a phase value of the first signal light for phase shifting according to the direct-current voltage value by the phase shifter.

In this embodiment, another way of determining the estimated phase difference is provided to ensure that the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is the preset phase difference, so that the occurrence of the situation of coherence cancellation is avoided, and the flexibility of the scheme is improved on the basis of improving the reliability of the scheme.

In an optional manner of the first aspect, the second microcontroller unit is specifically configured to calculate a ratio of the integrated second electrical signal and the integrated third electrical signal to obtain an estimated phase difference.

In this embodiment, the estimated phase difference is specifically determined by calculating a ratio of the integrated second electrical signal to the integrated third electrical signal, thereby improving the feasibility of the scheme.

In an optional manner of the first aspect, the coherent receiving apparatus further includes a second fourier transform module, a third microcontroller unit, and a third digital-to-analog converter. Based on this, when the phase shifter shifts the phase of the first signal light, the first pilot signal is loaded on a preset frequency point of the first signal light, the second fourier transform module extracts the first digital electrical signal from the digital electrical signal with the amplitude value adjusted, the second fourier transform module performs fourier transform on the first digital electrical signal to obtain the first digital electrical signal after fourier transform, the third microcontroller unit extracts a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal from the first digital electrical signal after fourier transform, the third microcontroller unit determines an estimated phase difference according to the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal, and determines a feedback control quantity according to the estimated phase difference and the preset phase difference. The third digital-to-analog converter converts the feedback control quantity into a direct-current voltage value, loads the direct-current voltage value to the phase shifter, and determines a phase value of the first signal light for phase shifting according to the direct-current voltage value.

In an optional manner of the first aspect, the coherent receiving apparatus further comprises a register and a frequency shifting module. The first analog-to-digital conversion module registers the digital electric signal with the adjusted amplitude value in a register, the register registers the digital electric signal with the adjusted amplitude value, the frequency shift module extracts the first digital electric signal from the digital electric signal with the adjusted amplitude value, the frequency shift module performs frequency shift processing on the first digital electric signal to obtain the first digital electric signal after frequency shift, the time domain averaging module averages the first digital electric signal after frequency shift in the time domain to obtain the first digital electric signal after time domain averaging, and the second Fourier conversion module performs Fourier transform on the first digital electric signal after time domain averaging to obtain the first digital electric signal after Fourier transform.

In an optional manner of the first aspect, the third microcontroller unit is specifically configured to calculate a ratio of a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal to obtain the estimated phase difference.

A second aspect of the present application provides a method of coherent reception. The method comprises the following steps: receiving signal light, decomposing the signal light into first signal light and second signal light, wherein the first signal light and the second signal light have the same polarization state, then performing phase shifting on the first signal light to obtain the phase-shifted first signal light, the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference, then combining the phase-shifted first signal light and the phase-shifted second signal light to obtain the combined signal light, generating local oscillator light, wherein the local oscillator light and the combined signal light have the same polarization state, and finally performing optical mixing on the combined signal light and the local oscillator light to obtain the mixed signal light.

In an optional manner of the second aspect, the signal light is subjected to polarization orthogonal decomposition to obtain a second signal light and a third signal light, and then the third signal light is fixedly rotated to obtain the first signal light.

In an alternative form of the second aspect, the predetermined phase difference is 0 °, or 90 °.

In an optional manner of the second aspect, the signal light after frequency mixing can be further subjected to photoelectric conversion to obtain an analog electrical signal after photoelectric conversion, the amplitude value of the analog electrical signal after photoelectric conversion is adjusted to obtain an analog electrical signal after amplitude value adjustment, and the analog electrical signal after amplitude value adjustment is subjected to analog-to-digital conversion to obtain a digital electrical signal after amplitude value adjustment.

In an optional manner of the second aspect, when the first signal light is phase-shifted, a first pilot signal may be loaded at a preset frequency point of the first signal light, the combined signal light is then divided into a fourth signal light and a fifth signal light, the fifth signal light is subjected to photoelectric conversion to obtain a first electrical signal, an estimated phase difference between the first signal light and the second signal light is calculated based on the first pilot signal, a feedback control amount is determined according to the estimated phase difference and the preset phase difference, and a phase value of the first signal light for phase shifting is determined through the feedback control amount.

In an optional manner of the second aspect, the first electrical signal is sampled to obtain a sampled time domain digital signal, the sampled time domain digital signal is subjected to fourier transform to obtain a frequency domain digital signal, a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal are further extracted from the frequency domain digital signal, so that an estimated phase difference is determined according to the first harmonic component of the first pilot signal and the second harmonic component of the first pilot signal, a feedback control quantity is determined according to the estimated phase difference and a preset phase difference, and the feedback control quantity is converted into a direct current voltage value, so that a phase value for shifting the phase of the first signal light can be determined according to the direct current voltage value.

In an alternative form of the second aspect, the estimated phase difference is obtained by calculating a ratio of a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal.

In an optional manner of the second aspect, the first electrical signal may be further divided into a second electrical signal and a third electrical signal, then the second electrical signal is low-pass filtered to obtain a low-pass filtered second electrical signal, and the low-pass filtered second electrical signal is multiplied by the first pilot signal in an analog domain to obtain a multiplied second electrical signal, and then the multiplied second electrical signal is integrated to obtain an integrated second electrical signal. Similarly, the third electrical signal is low-pass filtered to obtain a low-pass filtered third electrical signal, the low-pass filtered third electrical signal is multiplied by the frequency multiplication signal of the first pilot signal in the analog domain to obtain a multiplied third electrical signal, and the multiplied third electrical signal is further subjected to integration processing to obtain an integrated third electrical signal. Based on the phase value, the estimated phase difference is determined according to the integrated second electric signal and the integrated third electric signal, the feedback control quantity is determined according to the estimated phase difference and the preset phase difference, and then the feedback control quantity is converted into a direct current voltage value, so that the phase value of the first signal light for phase shifting is determined through the direct current voltage value.

In an alternative form of the second aspect, the estimated phase difference is obtained by calculating a ratio of the integrated second electrical signal and the integrated third electrical signal.

In an optional manner of the second aspect, when the first signal light is phase-shifted, a first pilot signal is loaded at a preset frequency point of the first signal light, based on which, a first digital electrical signal is extracted from the digital electrical signal after the amplitude value is adjusted, and fourier transform is performed on the first digital electrical signal to obtain a first digital electrical signal after fourier transform, a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal are extracted from the first digital electrical signal after fourier transform, an estimated phase difference is determined according to the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal, a feedback control quantity is determined according to the estimated phase difference and the preset phase difference, and then the feedback control quantity is converted into a direct-current voltage value, so that a phase value for phase-shifting of the first signal light is determined through the direct-current voltage value.

In an alternative of the second aspect, the estimated phase difference is obtained by calculating a ratio of a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal.

A third aspect of the present application provides a coherent communication system, which includes a coherent transmitting apparatus and a coherent receiving apparatus;

coherent transmitting means for generating signal light of a single polarization state and transmitting the signal light of the single polarization state to coherent receiving means;

coherent receiving means for receiving signal light of a single polarization state and performing the method according to any one of the embodiments of the first aspect or the second aspect.

Drawings

FIG. 1 is a schematic view of a scenario of a coherent communication system in the field of optical communication;

fig. 2 is a schematic structural diagram of a coherent receiving apparatus provided in the present application;

fig. 3 is another schematic structural diagram of a coherent receiving apparatus provided in the present application;

fig. 4 is another schematic structural diagram of a coherent receiving apparatus provided in the present application;

fig. 5 is another structural diagram of the coherent receiving apparatus provided in the present application.

Detailed Description

The application provides a coherent receiving device, a coherent receiving method and a related system. The coherent receiving device in this application is through shifting the phase to the first signal light after the decomposition for the first signal light after shifting the phase keeps predetermined phase difference with the second signal light that has the same polarization state, and with the first signal light after shifting the phase and the second signal light that has the same polarization state are combined beam, do not need respectively to receive the signal light of two polarization components promptly, thereby need not respectively to handle first signal light and second signal light, from this less quantity of optics and electronic component in the coherent optical module, thereby can reduce size and the consumption of coherent receiving device and coherent optical module.

It is to be understood that the use of "first," "second," etc. in the description of the embodiments of the present application is for purposes of distinguishing between the descriptions and is not intended to indicate or imply relative importance nor order to be construed. In addition, reference numerals and/or letters are repeated throughout the various embodiments of the present application for the sake of brevity and clarity. Repetition does not indicate a strict, restrictive relationship between the various embodiments and/or configurations.

In order to reduce the size and power consumption of coherent optical modules, single polarization coherent systems can be used to reduce the number of optical and electronic components involved, for example, one-way modulator is used on the transmitting side to generate a single-polarization high-order modulation signal, and the number of modulators and corresponding electrical components on the transmitting side is halved. However, after a single-polarization signal is transmitted through an optical fiber link, the signal becomes elliptically polarized light with a certain polarization angle before entering a receiving side, the single-polarization signal is orthogonally decomposed into two polarization components of X and Y, the local oscillation light output by the local oscillation laser included in the coherent receiver is linearly polarized light, and if the linearly polarized light is aligned with the X polarization component, the Y polarization component of the signal light orthogonal to the polarization state of the local oscillation light cannot be received. Based on this, only halving the optical and electronic components on the receiving side may result in a situation where only a part of the signal light is received or no signal light is received at all, so the coherent receiver still needs to adopt a polarization diversity front end to meet the requirement of being able to receive signals of two polarization components simultaneously, i.e. the optical and electronic components on the receiving side cannot be reduced, resulting in a limited reduction in cost, size and power consumption of the coherent optical module.

In order to solve the foregoing problems, the present application provides a coherent receiving apparatus, and is applied to a coherent communication system, which is described below first, fig. 1 is a schematic view of a coherent communication system in the field of optical communication, as shown in fig. 1, the coherent communication system includes a coherent transmitting apparatus 501 and a coherent receiving apparatus 502, the coherent transmitting apparatus 501 is configured to generate signal light in a single polarization state, and then the coherent receiving apparatus 502 receives the signal light in the single polarization state. Specifically, the signal light of a single polarization state generated by the coherent transmitting device 501 may be processed by using a high-order modulation format, which is a method of loading information by using multiple degrees of freedom, such as the phase and the amplitude of an optical carrier, so that the spectral efficiency of coherent optical communication can be improved.

Specifically, the coherent transmitter 501 includes a digital signal processing module 503, a digital-to-analog converter (DAC) 504, a driver 505, a modulator 506, and a laser 507. Based on this, the original bit data stream (e.g. including 0 and 1) is first subjected to source coding operation, bit mapping operation and certain pre-compensation in the digital signal processing module 503 to generate digital symbol information, and then converted into an analog electrical signal via the digital-to-analog converter 504. After the analog electrical signal is amplified by the driver 505, the amplified analog electrical signal is loaded onto the modulator 506, and the laser 507 sends an optical carrier to the modulator 506, so that the amplified analog electrical signal is modulated onto the optical carrier by the modulator 506, and the electro-optical conversion is completed, thereby obtaining signal light suitable for the transmission of the optical fiber channel. Second, modulator 506 may specifically be an in-phase quadrature (IQ) modulator or a mach-zehnder modulator in this application due to the need to generate higher order modulated signal light of a single polarization state.

Based on the coherent communication system described above, a coherent receiving apparatus of the coherent communication system in the present application is described below. Fig. 2 is a schematic structural diagram of a coherent receiving apparatus provided in this application, and as shown in fig. 2, the coherent receiving apparatus includes a polarization beam splitting and rotating module 101, a phase shifter 102, a coupler 103, a mixer 104, a laser 105, a balanced receiver (BPD) 106, a trans-impedance amplifier (TIA) 107, a first analog-to-digital converter (ADC) 108, and a digital signal processing module 109.

The polarization beam splitting and rotating module 101 is configured to receive signal light, perform polarization orthogonal decomposition on the received signal light to obtain two polarization components with orthogonal polarization states, then fixedly rotate the polarization state of one polarization component to align with the polarization state of the other polarization component, finally obtain two polarization components with the same polarization state, that is, obtain a first signal light and a second signal light with the same polarization state, then send the decomposed first signal light to the phase shifter 102, and send the decomposed second signal light to the coupler 103.

Optionally, the polarization beam splitting rotation module 101 is a polarization beam splitting rotator (PSR).

Optionally, the polarization beam splitting and rotating module 101 includes a Polarization Beam Splitter (PBS) and a Polarization Rotator (PR). The PBS is used for carrying out polarization orthogonal decomposition on the received signal light to obtain second signal light and third signal light, and based on the second signal light and the third signal light, the PR is used for fixedly rotating the third signal light to obtain the first signal light.

After receiving the first signal light sent by the polarization beam splitting and rotating module 101, the phase shifter 102 shifts the phase of the first signal light to obtain the first signal light after shifting the phase, and a phase difference between the first signal light after shifting the phase and the second signal light is a preset phase difference to ensure that the first signal light after shifting the phase and the second signal light after shifting the phase always satisfy a specific phase relationship. Based on this, the phase shifter 102 sends the phase-shifted first signal light to the coupler 103.

Specifically, the preset phase difference is 0 °, or 90 °. It should be understood that, since the preset phase difference can be a range in practical application, an error within ± 10 ° to ± 20 ° from the preset phase difference is acceptable based on the actual error and the precision of the technical means. Therefore, the phase difference between the phase-shifted first signal light and the phase-shifted second signal light may be 0 °, or a phase value close to 0 °, for example, -5 °, -10 °, and 5 °, and so on. Similarly, the phase difference between the phase-shifted first signal light and the phase-shifted second signal light may be a phase value of 90 ° or approximately 90 °, for example, 95 °,100 °, 85 °, and the like, and when the phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a phase value of 90 ° or approximately 90 °, constructive superposition can be satisfied, so that the signal is received to the maximum extent.

Specifically, the phase of the first signal light shifted by the phase shifter 102 is changed by a value at least satisfying 0 ° to 360 °.

Alternatively, the phase shifter 102 may have a single-arm structure, and may also have a push-pull structure of upper and lower arms, which is not limited herein.

Specifically, the phase shifter 102 may modulate the refractive index of the phase shift region in various manners such as thermo-optical, electro-optical, and magneto-optical, so as to shift the phase of the first signal light.

Specifically, due to factors such as process manufacturing and material refractive index constraints, a single-stage phase shifter may not achieve a completely linear phase shift effect of 0 ° to 360 °, and a cascade multi-stage phase shifter is required, in this embodiment, the maximum cascade can reach 5 stages. Based on this, the phase shifter 102 may be implemented by a multi-stage mach-zehnder interference structure plus a plurality of phase shifters cascaded.

A coupler 103, which, after receiving the second signal light sent by the polarization beam splitting and rotating module 101 and the phase-shifted first signal light sent by the phase shifter 102, combines the phase-shifted first signal light and the phase-shifted second signal light to obtain combined signal light, and sends the combined signal light to the mixer 104;

the laser 105 is capable of generating local oscillation light having the same polarization state as the combined signal light, and then transmits the generated local oscillation light to the mixer 104.

The mixer 104 receives the combined signal light transmitted by the coupler 103 and the local oscillator light transmitted by the laser 105, optically mixes the combined signal light with the local oscillator light to obtain mixed signal light, and transmits the mixed signal light to the balanced receiver 106. Specifically, the signal light after being mixed sent by the mixer 104 is 4 signal lights, and the phase difference between each two signal lights is 90 °.

The balanced receiver 106, upon receiving the mixed signal light transmitted by the mixer 104, performs photoelectric conversion on the mixed signal light to obtain a photoelectric-converted analog electrical signal, and transmits the photoelectric-converted analog electrical signal to the transimpedance amplifier 107.

The transimpedance amplifier 107, after receiving the analog electrical signal after photoelectric conversion sent by the balanced receiver 106, adjusts the amplitude value of the analog electrical signal after photoelectric conversion to obtain an analog electrical signal after amplitude value adjustment, and sends the analog electrical signal after amplitude value adjustment to the first analog-to-digital converter 108.

After receiving the analog electrical signal with the adjusted amplitude value sent by the transimpedance amplifier 107, the first analog-to-digital converter 108 performs analog-to-digital conversion on the analog electrical signal with the adjusted amplitude value to obtain a digital electrical signal with the adjusted amplitude value, and sends the digital electrical signal with the adjusted amplitude value to the digital signal processing module 109. Based on this, the digital signal processing module 109 performs data processing on the amplitude-adjusted digital electrical signal.

In the coherent receiving device 100 described in fig. 2, the polarization beam splitting rotation module 101, the phase shifter 102, the coupler 103, the mixer 104 and the balanced receiver 106 constitute an optical front end of the coherent receiving device 100, and it should be understood that the polarization beam splitting rotation module 101, the phase shifter 102, the coupler 103, the mixer 104 and the balanced receiver 106 may be implemented by separate device assemblies, or may be implemented by other monolithic integration such as silicon-based monolithic integration (not limited to silicon-based waveguide) or indium phosphide-based monolithic integration, and is not limited herein.

In practical application, the phase shifter can adjust the phase value of the first signal light for phase shifting in real time, specifically, a feedback control quantity is obtained through calculation, a direct current voltage value capable of being loaded on the phase shifter is determined through the feedback control quantity, and then the phase value of the first signal light for phase shifting is determined according to the direct current voltage value. Based on the coherent receiving apparatus shown in fig. 2, the manner of obtaining the dc voltage value will be described in detail below.

In one possible implementation manner, please refer to fig. 3, fig. 3 is a schematic structural diagram of a coherent receiving apparatus provided in the present application, and as shown in fig. 3, the coherent receiving apparatus includes a polarization beam splitting rotation module 201, a phase shifter 202, a coupler 203, a mixer 204, a photoelectric conversion module 205, a feedback control module 206, a laser 207, a balanced receiver 208, a transimpedance amplifier 209, a first analog-to-digital converter 210, and a digital signal processing module 211. The feedback control module 206 specifically includes a second analog-to-digital converter 212, a first fourier transform module 213, a first Micro Controller Unit (MCU) 214, and a first digital-to-analog converter 215.

The polarization beam splitting and rotating module 201 is configured to receive signal light, perform polarization orthogonal decomposition on the received signal light to obtain two polarization components with orthogonal polarization states, then fixedly rotate the polarization state of one polarization component to align with the polarization state of the other polarization component, finally obtain two polarization components with the same polarization state, that is, obtain a first signal light and a second signal light with the same polarization state, then send the decomposed first signal light to the phase shifter 202, and send the decomposed second signal light to the coupler 203.

Optionally, the polarization beam splitting rotation module 201 is a PSR.

Optionally, the polarization beam splitting rotation module 201 includes PBS and PR. The PBS is used for carrying out polarization orthogonal decomposition on the received signal light to obtain second signal light and third signal light, and based on the second signal light and the third signal light, the PR is used for fixedly rotating the third signal light to obtain the first signal light.

After receiving the first signal light sent by the polarization beam splitting rotation module 201, the phase shifter 202 shifts the phase of the first signal light to obtain the phase-shifted first signal light, and a phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference to ensure that the phase-shifted first signal light and the phase-shifted second signal light always satisfy a specific phase relationship. Further, when the phase shifter 202 shifts the phase of the first signal light, it is also able to load a first pilot signal on a preset frequency point of the first signal light, where the frequency of the first pilot signal is fd, and a value of fd in this embodiment is between tens of kilohertz (KHz) and tens of megahertz (MHz). Based on this, the phase shifter 202 sends the phase-shifted first signal light to the coupler 203, and the first pilot signal is loaded on the phase-shifted first signal light.

Specifically, the phase of the first signal light shifted by the phase shifter 202 is changed by a value at least satisfying 0 ° to 360 °.

Alternatively, the phase shifter 202 may have a single-arm structure, and may also have a push-pull structure for upper and lower arms, which is not limited herein.

Specifically, the phase shifter 202 may modulate the refractive index of the phase shift region in various manners such as thermo-optic, electro-optic, and magneto-optic, so as to shift the phase of the first signal light.

Specifically, due to factors such as process manufacturing and material refractive index constraints, a single-stage phase shifter may not achieve a completely linear phase shift effect of 0 ° to 360 °, a multi-stage phase shifter needs to be cascaded, and the maximum cascade in this embodiment can reach 5 stages. Based on this, the phase shifter 202 may be implemented by a multi-stage mach-zehnder interference structure plus a plurality of phase shifters cascaded.

After receiving the second signal light sent by the polarization beam splitting and rotating module 201 and the phase-shifted first signal light sent by the phase shifter 202, the coupler 203 combines the phase-shifted first signal light and the phase-shifted second signal light to obtain a combined signal light. Further, the combined signal light is further divided into a fourth signal light and a fifth signal light, and the fourth signal light is transmitted to the mixer 204, and the fifth signal light is transmitted to the photoelectric conversion module 205.

The laser 207 can generate local oscillation light having the same polarization state as the fourth signal light, and then transmit the generated local oscillation light to the mixer 204.

The mixer 204, after receiving the fourth signal light transmitted by the coupler 203 and the local oscillator light transmitted by the laser 207, optically mixes the fourth signal light with the local oscillator light to obtain mixed signal light, and transmits the mixed signal light to the balanced receiver 208. Specifically, the signal light after being mixed sent by the mixer 204 is 4 signal lights, and the phase difference between each two signal lights is 90 °.

The balanced receiver 208, upon receiving the mixed signal light transmitted by the mixer 204, performs photoelectric conversion on the mixed signal light to obtain a photoelectric-converted analog electrical signal, and transmits the photoelectric-converted analog electrical signal to the transimpedance amplifier 209.

The transimpedance amplifier 209, upon receiving the analog electrical signal after photoelectric conversion sent by the balanced receiver 208, adjusts the amplitude value of the analog electrical signal after photoelectric conversion to obtain an analog electrical signal after amplitude value adjustment, and sends the analog electrical signal after amplitude value adjustment to the first analog-to-digital converter 210.

After receiving the analog electrical signal with the adjusted amplitude value sent by the transimpedance amplifier 209, the first analog-to-digital converter 210 performs analog-to-digital conversion on the analog electrical signal with the adjusted amplitude value to obtain a digital electrical signal with the adjusted amplitude value, and sends the digital electrical signal with the adjusted amplitude value to the digital signal processing module 211. Based on this, the digital signal processing module 211 performs data processing on the amplitude-adjusted digital electrical signal.

In order to adjust the phase value of the first signal light in real time, after receiving the fifth signal light sent by the coupler 203, the optical-to-electrical conversion module 205 performs optical-to-electrical conversion on the fifth signal light to obtain a first electrical signal, where the first electrical signal includes a first pilot signal, it should be understood that a bandwidth of the optical-to-electrical conversion module 205 is greater than a bandwidth of the first pilot signal, and then, due to the optical-to-electrical conversion, the first pilot signal included in the first electrical signal is a signal with damage and fading compared with the first pilot signal included in the first signal light, so that the first pilot signal included in the first electrical signal and the first pilot signal included in the first signal light may not be completely the same. Based on this, the photoelectric conversion module 205 sends the first electrical signal to the feedback control module 206, and specifically, the photoelectric conversion module 205 sends the first electrical signal to the second analog-to-digital converter 212 included in the feedback control module 206. Specifically, the photoelectric conversion module 205 described in this embodiment is a monitor photodiode (mPD).

The second analog-to-digital converter 212 comprised by the feedback control module 206 samples the received first electrical signal and sends the sampled time-domain digital signal to the first fourier transform module 213 comprised by the feedback control module 206.

The first Fourier transform module 213 included in the feedback control module 206 performs Fast Fourier Transform (FFT) on the sampled time domain digital signal to a frequency domain to obtain a frequency domain digital signal, and sends the frequency domain digital signal to the first microcontroller unit 214 included in the feedback control module 206.

The first microcontroller unit 214 comprised by the feedback control module 206 extracts a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal from the received frequency domain digital signal. Then, the estimated phase difference is determined according to the first harmonic component of the first pilot signal and the second harmonic component of the first pilot signal, and specifically, the first microcontroller unit 214 obtains the estimated phase difference by calculating a ratio of the first harmonic component of the first pilot signal and the second harmonic component of the first pilot signal. And then, according to the difference between the estimated phase difference and the preset phase difference, the feedback control quantity is obtained. Based on this, the first microcontroller unit 214 sends the determined feedback control amount to the first digital-to-analog converter 215 included in the feedback control module 206.

The first digital-to-analog converter 215 included in the feedback control module 206 converts the received feedback control amount into a dc voltage value and applies the dc voltage value to the phase shifter 202. Specifically, the first digital-to-analog converter 215 applies the dc voltage value to the phase shifter 202 together with the ac voltage corresponding to the first pilot signal. Based on this, the phase shifter 202 can determine the phase value of the first signal light for phase shifting according to the loaded dc voltage value and the ac voltage corresponding to the first pilot signal, so that the dc voltage value can be adjusted in real time according to the feedback control quantity obtained by the signal transmission channel condition, so as to ensure that the phase-shifted first signal light and the phase-shifted second signal light always satisfy a specific phase relationship.

In the coherent receiving device 200 described in fig. 3, the polarization beam splitting rotation module 201, the phase shifter 202, the coupler 203, the mixer 204, the photoelectric conversion module 205 and the balanced receiver 208 constitute an optical front end of the coherent receiving device 200, and it should be understood that the polarization beam splitting rotation module 201, the phase shifter 202, the coupler 203, the mixer 204, the photoelectric conversion module 205 and the balanced receiver 208 may be implemented by separate device assemblies or by silicon-based monolithic integration (not limited to silicon-based waveguides), which is not limited herein.

In one possible implementation manner, referring to fig. 4, fig. 4 is a schematic structural diagram of a coherent receiving apparatus provided in the present application, and as shown in fig. 4, the coherent receiving apparatus includes a polarization beam splitting rotation module 301, a phase shifter 302, a coupler 303, a mixer 304, a photoelectric conversion module 305, a feedback control module 306, a laser 307, a balanced receiver 308, a transimpedance amplifier 309, a first analog-to-digital converter 310, and a digital signal processing module 311. The feedback control module 306 specifically includes a first low-pass filter (LPF) 312, a first multiplier 313, a first integrator 314, a second low-pass filter 315, a second multiplier 316, a second integrator 317, a second microcontroller unit 318, and a second digital-to-analog converter 319.

The polarization beam splitting and rotating module 301, the phase shifter 302, the coupler 303, the mixer 304, the laser 307, the balanced receiver 308, the transimpedance amplifier 309, the first analog-to-digital converter 310, and the digital signal processing module 311 have functions similar to those of the polarization beam splitting and rotating module 201, the phase shifter 202, the coupler 203, the mixer 204, the laser 207, the balanced receiver 208, the transimpedance amplifier 209, the first analog-to-digital converter 210, and the digital signal processing module 211 in the embodiment of fig. 3, and are not described herein again with reference to the above description.

In order to adjust the phase value of the first signal light, after receiving the fifth signal light transmitted by the coupler 303, the optical-to-electrical conversion module 305 performs optical-to-electrical conversion on the fifth signal light to obtain a first electrical signal, where the first electrical signal includes a first pilot signal, and then, since the first pilot signal included in the first electrical signal is a damaged or fading signal compared with the first pilot signal included in the first signal light through the optical-to-electrical conversion, the first pilot signal included in the first electrical signal cannot be completely identical to the first pilot signal included in the first signal light, which should not be construed as a limitation of the present solution. Based on this, the photoelectric conversion module 305 further divides the first electrical signal into a second electrical signal and a third electrical signal, and sends the second electrical signal and the third electrical signal to the feedback control module 306. Specifically, the photoelectric conversion module 305 sends the second electric signal to a first low-pass filter 312 included in the feedback control module 306, and sends the third electric signal to a second low-pass filter 315 included in the feedback control module 306. Specifically, the photoelectric conversion module 305 described in this embodiment is mPD.

The first low-pass filter 312 included in the feedback control module 306 low-pass filters the received second electric signal to obtain a low-pass filtered second electric signal, and then sends the low-pass filtered second electric signal to the first multiplier 313 included in the feedback control module 306.

The first multiplier 313 included in the feedback control module 306 multiplies the received low-pass filtered second electrical signal by the first pilot signal in the analog domain to obtain a multiplied second electrical signal, and sends the multiplied second electrical signal to the first integrator 314 included in the feedback control module 306, where the frequency of the first pilot signal is fd.

The first integrator 314 comprised by the feedback control module 306 integrates the multiplied second electrical signal to obtain an integrated second electrical signal and sends the integrated second electrical signal to a second microcontroller unit 318 comprised by the feedback control module 306.

A second low pass filter 315 included in the feedback control module 306 low pass filters the received third electrical signal to obtain a low pass filtered third electrical signal, which is then sent to a second multiplier 316 included in the feedback control module 306.

The second multiplier 316 included in the feedback control module 306 multiplies the received low-pass filtered third electrical signal by the frequency multiplication signal of the first pilot signal in the analog domain to obtain a multiplied third electrical signal, and sends the multiplied third electrical signal to the second integrator 317 included in the feedback control module 306. Specifically, the frequency of the first pilot signal has a correlation with the frequency of the frequency multiplication signal of the first pilot signal, for example, on the basis that the frequency of the first pilot signal is fd, the frequency of the frequency multiplication signal of the first pilot signal is 2fd, or a frequency close to 2fd, which is not limited herein. Secondly, the frequency multiplication signal of the first pilot signal is obtained by frequency multiplication processing of the first pilot signal by a frequency multiplier, and the coherent receiving apparatus shown in fig. 4 does not specifically show the frequency multiplier, which should not be construed as a limitation of the scheme herein.

The second integrator 317 included in the feedback control module 306 integrates the multiplied third electrical signal to obtain an integrated third electrical signal, and sends the integrated third electrical signal to the second microcontroller unit 318 included in the feedback control module 306.

The second microcontroller unit 318 included in the feedback control module 306 determines the estimated phase difference according to the received integrated second electrical signal and the integrated third electrical signal, specifically, the second microcontroller unit 318 obtains the estimated phase difference by calculating a ratio of the integrated second electrical signal and the integrated third electrical signal. Based on this, the feedback control amount is obtained according to the difference between the estimated phase difference and the preset phase difference, and is sent to the second digital-to-analog converter 319 included in the feedback control module 306.

The second digital-to-analog converter 319 included in the feedback control module 306 converts the received feedback control amount into a direct-current voltage value, and loads the direct-current voltage value onto the phase shifter 302. Specifically, the second digital-to-analog converter 319 applies the dc voltage value to the phase shifter 302 together with the ac voltage corresponding to the first pilot signal. Based on this, the phase shifter 302 can determine the phase value of the first signal light for phase shifting according to the loaded dc voltage value and the ac voltage corresponding to the first pilot signal, so that the dc voltage value can be adjusted in real time according to the feedback control quantity obtained by the signal transmission channel condition, so as to ensure that the phase-shifted first signal light and the phase-shifted second signal light always satisfy a specific phase relationship.

In the coherent receiving device 300 described in fig. 4, the polarization beam splitting rotation module 301, the phase shifter 302, the coupler 303, the mixer 304, the photoelectric conversion module 305 and the balanced receiver 308 constitute an optical front end of the coherent receiving device 300, and it should be understood that the polarization beam splitting rotation module 301, the phase shifter 302, the coupler 303, the mixer 304, the photoelectric conversion module 305 and the balanced receiver 308 may be implemented by separate device assembly or by silicon-based monolithic integration (not limited to silicon-based waveguides), which is not limited herein.

In one possible implementation manner, referring to fig. 5, fig. 5 is a schematic diagram of another structure of a coherent receiving apparatus provided in this application, and as shown in fig. 5, the coherent receiving apparatus includes a polarization beam splitting rotation module 401, a phase shifter 402, a coupler 403, a mixer 404, a laser 405, a balanced receiver 406, a transimpedance amplifier 407, a first analog-to-digital converter 408, a digital signal processing module 409, a register 410, a frequency shifting module 411, a time domain averaging module 412, a second fourier transform module 413, a third microcontroller unit 414, and a third digital-to-analog converter 415.

The polarization beam splitting and rotating module 401, the phase shifter 402, the coupler 403, the mixer 404, the laser 405, the balanced receiver 406, the transimpedance amplifier 407, and the digital signal processing module 409 are similar to the polarization beam splitting and rotating module 201, the phase shifter 202, the coupler 203, the mixer 204, the laser 207, the balanced receiver 208, the transimpedance amplifier 209, and the digital signal processing module 211 in the embodiment of fig. 2, respectively, and are not described herein again with reference to the above description.

After receiving the analog electrical signal with the adjusted amplitude value sent by the transimpedance amplifier 407, the first analog-to-digital converter 408 performs analog-to-digital conversion on the analog electrical signal with the adjusted amplitude value to obtain a digital electrical signal with the adjusted amplitude value, and sends the digital electrical signal with the adjusted amplitude value to the digital signal processing module 409. Based on this, the digital signal processing module 409 performs data processing on the digital electrical signal after the amplitude value is adjusted. Further, the first analog-to-digital converter 408 can also register the digital electrical signal with the adjusted amplitude value in the register 410.

In order to adjust the phase value for shifting the phase of the first signal light in real time, the register 410 registers the digital electrical signal after adjusting the amplitude value.

The frequency shift module 411 extracts a first digital electrical signal from the register 410, where the first digital electrical signal is any one of the digital electrical signals after the amplitude value is adjusted. Based on this, the frequency shift processing is performed on the first digital electrical signal to obtain a frequency-shifted first digital electrical signal, and the frequency-shifted first digital electrical signal is sent to the time domain averaging module 412.

The time domain averaging module 412 averages the received frequency-shifted first digital electrical signal in the time domain, specifically, performs a summation average of every M symbols in the time domain as one symbol in the FFT module, so as to obtain a time domain averaged first digital electrical signal, and based on this, sends the time domain averaged first digital electrical signal to the second fourier transform module 413.

The second fourier transform module 413 performs fourier transform on the received time domain averaged first digital electrical signal to obtain a fourier transformed first digital electrical signal, and based on this, sends the fourier transformed first digital electrical signal to the third microcontroller unit 414.

The third microcontroller unit 414 extracts the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal from the received fourier-transformed first digital electrical signal, and determines an estimated phase difference according to the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal, where the estimated phase difference is a phase difference between the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal, and specifically, the estimated phase difference is obtained by calculating a ratio of the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal. Based on this, the feedback control amount is obtained according to the difference between the estimated phase difference and the preset phase difference, and then the feedback control amount is sent to the third dac 415.

The third digital-to-analog converter 415 converts the received feedback control amount into a direct-current voltage value, and loads the direct-current voltage value to the phase shifter. Specifically, the third dac 415 applies the dc voltage value to the phase shifter 402 together with the ac voltage corresponding to the first pilot signal. Based on this, the phase shifter 402 can determine the phase value of the phase shift of the first signal light according to the loaded dc voltage value and the ac voltage corresponding to the first pilot signal, so that the dc voltage value can be adjusted in real time according to the feedback control quantity obtained by the signal transmission channel condition, so as to ensure that the phase-shifted first signal light and the phase-shifted second signal light always satisfy the specific phase relationship.

In the coherent receiving device 400 described in fig. 5, the polarization beam splitting rotation module 401, the phase shifter 402, the coupler 403, the mixer 404 and the balanced receiver 406 constitute an optical front end of the coherent receiving device 400, and it should be understood that the polarization beam splitting rotation module 401, the phase shifter 402, the coupler 403, the mixer 404 and the balanced receiver 406 may be implemented by separate device assemblies or by silicon-based monolithic integration (not limited to silicon-based waveguides), which is not limited herein.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application.

Claims

1. A coherent receiving device is characterized by comprising a polarization beam splitting and rotating module, a phase shifter, a coupler, a laser and a frequency mixer;

the polarization beam splitting and rotating module is used for receiving signal light and splitting the signal light into first signal light and second signal light, wherein the first signal light and the second signal light have the same polarization state;

the phase shifter is configured to shift the phase of the first signal light to obtain a phase-shifted first signal light, where a phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference;

the coupler is used for combining the first signal light and the second signal light after phase shifting to obtain combined signal light;

the laser is configured to send the generated local oscillator light to the mixer, where the local oscillator light and the combined signal light have the same polarization state;

and the frequency mixer is used for carrying out optical frequency mixing on the combined signal light and the local oscillator light to obtain the signal light after frequency mixing.

2. The coherent receiving device of claim 1, wherein the polarization beam splitting rotation module is a polarization beam splitting rotator PSR.

3. The coherent receiving device of claim 1, wherein the polarization beam splitting rotation module comprises a polarization beam splitter PBS and a polarization rotator PR;

the PBS is used for performing polarization orthogonal decomposition on the signal light to obtain second signal light and third signal light;

the PR is used for fixedly rotating the third signal light to obtain the first signal light.

4. The coherent receiving device of any one of claims 1 to 3, further comprising a balanced receiver, a transimpedance amplifier and a first analog-to-digital converter;

the balance receiver is used for performing photoelectric conversion on the signal light after the frequency mixing to obtain an analog electric signal after the photoelectric conversion;

the transimpedance amplifier is used for adjusting the amplitude value of the analog electric signal after the photoelectric conversion so as to obtain the analog electric signal after the amplitude value is adjusted;

the first analog-to-digital converter is used for performing analog-to-digital conversion on the analog electric signal with the adjusted amplitude value to obtain a digital electric signal with the adjusted amplitude value.

5. The coherent receiving device of claim 4, further comprising an optical-to-electrical conversion module and a feedback control module;

the phase shifter is further configured to load a first pilot signal on a preset frequency point of the first signal light when the first signal light is phase-shifted;

the coupler is specifically configured to divide the combined signal light into a fourth signal light and a fifth signal light;

the photoelectric conversion module is used for performing photoelectric conversion on the fifth signal light to obtain a first electric signal;

the feedback control module is configured to calculate an estimated phase difference between the first signal light and the second signal light based on the first pilot signal, and determine a feedback control amount according to the estimated phase difference and the preset phase difference;

the feedback control module is further configured to load the feedback control quantity onto the phase shifter;

the phase shifter is specifically configured to determine a phase value of the first signal light for phase shifting according to the feedback control amount.

6. The coherent receiving device of claim 5, wherein the feedback control module comprises a second analog-to-digital converter, a first Fourier transform module, a first microcontroller unit and a first digital-to-analog converter;

the second analog-to-digital converter is used for sampling the first electric signal to obtain a sampled time domain digital signal;

the first Fourier transform module is used for carrying out Fourier transform on the sampled time domain digital signal to obtain a frequency domain digital signal;

the first microcontroller unit for extracting a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal from the frequency domain digital signal;

the first microcontroller unit is further configured to determine the estimated phase difference according to a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal, and determine the feedback control amount according to the estimated phase difference and the preset phase difference;

the first digital-to-analog converter is used for converting the feedback control quantity into a direct current voltage value and loading the direct current voltage value onto the phase shifter;

the phase shifter is specifically configured to determine a phase value of the first signal light for phase shifting according to the dc voltage value.

7. The coherent receiving device of claim 6, wherein the first microcontroller unit is configured to calculate a ratio of a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal to obtain the estimated phase difference.

8. The coherent receiving device of claim 5, wherein the feedback control module comprises a first low pass filter, a first multiplier, a first integrator, a second low pass filter, a second multiplier, a second integrator, a second microcontroller unit, and a second digital-to-analog converter;

the photoelectric conversion module is further used for dividing the first electric signal into a second electric signal and a third electric signal;

the first low-pass filter is configured to perform low-pass filtering on the second electrical signal to obtain a low-pass filtered second electrical signal;

the first multiplier is configured to perform analog domain multiplication on the low-pass filtered second electrical signal and the first pilot signal to obtain a multiplied second electrical signal;

the first integrator is configured to perform integration processing on the multiplied second electric signal to obtain an integrated second electric signal;

the second low-pass filter is configured to perform low-pass filtering on the third electrical signal to obtain a low-pass filtered third electrical signal;

the second multiplier is configured to perform analog domain multiplication on the low-pass filtered third electrical signal and a frequency multiplication signal of the first pilot signal to obtain a multiplied third electrical signal;

the second integrator is configured to perform integration processing on the multiplied third electric signal to obtain an integrated third electric signal;

the second microcontroller unit is configured to determine the estimated phase difference according to the integrated second electrical signal and the integrated third electrical signal, and determine the feedback control amount according to the estimated phase difference and the preset phase difference;

the second digital-to-analog converter is used for converting the feedback control quantity into a direct-current voltage value and loading the direct-current voltage value onto the phase shifter;

9. The coherent receiving device of claim 8, wherein the second microcontroller unit is configured to calculate a ratio of the integrated second electrical signal and the integrated third electrical signal to obtain the estimated phase difference.

10. The coherent receiving device of claim 4, further comprising a second Fourier transform module, a third microcontroller unit and a third digital-to-analog converter;

the second Fourier transform module is used for extracting a first digital electric signal from the digital electric signal after the amplitude value is adjusted;

the second fourier transform module is further configured to perform fourier transform on the first digital electrical signal to obtain a fourier-transformed first digital electrical signal;

the third microcontroller unit is configured to extract a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal from the fourier-transformed first digital electrical signal;

the third microcontroller unit is further configured to determine the estimated phase difference according to a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal, and determine the feedback control amount according to the estimated phase difference and the preset phase difference;

the third digital-to-analog converter is used for converting the feedback control quantity into a direct current voltage value and loading the direct current voltage value onto the phase shifter;

11. The coherent receiving device of claim 10, wherein the third microcontroller unit is configured to calculate a ratio of a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal to obtain the estimated phase difference.

12. A method of coherent reception, comprising:

receiving signal light and decomposing the signal light into first signal light and second signal light, wherein the first signal light and the second signal light have the same polarization state;

performing phase shifting on the first signal light to obtain phase-shifted first signal light, wherein a phase difference between the phase-shifted first signal light and the phase-shifted second signal light is a preset phase difference;

combining the phase-shifted first signal light and the phase-shifted second signal light to obtain combined signal light;

generating local oscillator light, wherein the local oscillator light and the combined signal light have the same polarization state;

and carrying out optical frequency mixing on the combined signal light and the local oscillator light to obtain the signal light after frequency mixing.

13. The method of claim 12, wherein the splitting the signal light into a first signal light and a second signal light comprises:

performing polarization orthogonal decomposition on the signal light to obtain second signal light and third signal light;

and fixedly rotating the third signal light to obtain the first signal light.

14. The method according to claim 12 or 13, characterized in that the method further comprises:

performing photoelectric conversion on the mixed signal light to obtain a photoelectric-converted analog electric signal;

adjusting the amplitude value of the analog electric signal after the photoelectric conversion to obtain the analog electric signal after the amplitude value is adjusted;

and performing analog-to-digital conversion on the analog electric signal with the amplitude value adjusted to obtain a digital electric signal with the amplitude value adjusted.

15. The method of claim 14, further comprising:

loading a first pilot signal on a preset frequency point of the first signal light when the first signal light is subjected to phase shifting;

dividing the combined signal light into a fourth signal light and a fifth signal light;

performing photoelectric conversion on the fifth signal light to obtain a first electric signal;

calculating to obtain an estimated phase difference between the first signal light and the second signal light based on the first pilot signal, and determining a feedback control quantity according to the estimated phase difference and the preset phase difference;

and determining a phase value of the first signal light for phase shifting through the feedback control quantity.

16. The method according to claim 15, wherein the calculating an estimated phase difference between the first signal light and the second signal light based on the first pilot signal, and determining a feedback control amount according to the estimated phase difference and the preset phase difference comprises:

sampling the first electric signal to obtain a sampled time domain digital signal;

carrying out Fourier transform on the sampled time domain digital signal to obtain a frequency domain digital signal;

extracting a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal from the frequency domain digital signal;

determining the estimated phase difference according to a first harmonic component of the first pilot signal and a second harmonic component of the first pilot signal, and determining the feedback control quantity according to the estimated phase difference and the preset phase difference;

converting the feedback control quantity into a direct-current voltage value;

the determining, by the feedback control amount, a phase value at which the first signal light is phase-shifted includes:

and determining a phase value of the first signal light for phase shifting according to the direct-current voltage value.

17. The method of claim 16, wherein determining the estimated phase difference based on the first harmonic component of the first pilot signal and the second harmonic component of the first pilot signal comprises:

and calculating the ratio of the first harmonic component of the first pilot signal and the second harmonic component of the first pilot signal to obtain the estimated phase difference.

18. The method of claim 15, further comprising:

splitting the first electrical signal into a second electrical signal and a third electrical signal;

the calculating an estimated phase difference between the first signal light and the second signal light based on the first pilot signal, and determining a feedback control amount according to the estimated phase difference and the preset phase difference includes:

low-pass filtering the second electrical signal to obtain a low-pass filtered second electrical signal;

performing analog domain multiplication on the low-pass filtered second electric signal and the first pilot signal to obtain a multiplied second electric signal;

integrating the multiplied second electric signal to obtain an integrated second electric signal;

low-pass filtering the third electrical signal to obtain a low-pass filtered third electrical signal;

performing analog domain multiplication on the low-pass filtered third electric signal and a frequency multiplication signal of the first pilot signal to obtain a multiplied third electric signal;

performing integral processing on the multiplied third electric signal to obtain an integrated third electric signal;

determining the estimated phase difference according to the integrated second electric signal and the integrated third electric signal, and determining the feedback control quantity according to the estimated phase difference and the preset phase difference;

converting the feedback control quantity into a direct current voltage value;

19. The method of claim 18, wherein determining the estimated phase difference from the integrated second electrical signal and the integrated third electrical signal comprises:

and calculating the ratio of the integrated second electric signal to the integrated third electric signal to obtain the estimated phase difference.

20. The method of claim 14, further comprising:

extracting a first digital electric signal from the digital electric signal after the amplitude value is adjusted;

performing Fourier transform on the first digital electric signal to obtain a Fourier-transformed first digital electric signal;

a third harmonic component of the first pilot signal and a fourth harmonic component of the first pilot signal extracted from the fourier-transformed first digital electrical signal;

determining the estimated phase difference according to the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal, and determining the feedback control quantity according to the estimated phase difference and the preset phase difference;

converting the feedback control quantity into a direct current voltage value;

21. The method of claim 20, wherein determining the estimated phase difference based on the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal comprises:

and calculating the ratio of the third harmonic component of the first pilot signal and the fourth harmonic component of the first pilot signal to obtain the estimated phase difference.

22. A coherent communication system, comprising a coherent transmitting apparatus and a coherent receiving apparatus;

the coherent transmitting device is configured to generate signal light in a single polarization state and transmit the signal light in the single polarization state to the coherent receiving device;

the coherent receiving device, configured to receive the signal light in the single polarization state, and perform the method according to any one of claims 12 to 21.