WO2021135428A1 - 相干光接收装置和采用相干光接收装置的光*** - Google Patents

相干光接收装置和采用相干光接收装置的光*** Download PDF

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Publication number
WO2021135428A1
WO2021135428A1 PCT/CN2020/117043 CN2020117043W WO2021135428A1 WO 2021135428 A1 WO2021135428 A1 WO 2021135428A1 CN 2020117043 W CN2020117043 W CN 2020117043W WO 2021135428 A1 WO2021135428 A1 WO 2021135428A1
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Prior art keywords
light
sub
local oscillator
signal
polarization
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PCT/CN2020/117043
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English (en)
French (fr)
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桂韬
李良川
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华为技术有限公司
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Priority to JP2022540549A priority Critical patent/JP7427094B2/ja
Priority to EP20910106.2A priority patent/EP4072041A4/en
Publication of WO2021135428A1 publication Critical patent/WO2021135428A1/zh
Priority to US17/853,067 priority patent/US11817908B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/615—Arrangements affecting the optical part of the receiver
    • H04B10/6151—Arrangements affecting the optical part of the receiver comprising a polarization controller at the receiver's input stage
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H04B10/25752—Optical arrangements for wireless networks
    • H04B10/25758—Optical arrangements for wireless networks between a central unit and a single remote unit by means of an optical fibre
    • H04B10/25759—Details of the reception of RF signal or the optical conversion before the optical fibre
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/614—Coherent receivers comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • This application relates to the field of optical communications, and in particular to a coherent light receiving device and an optical system using the coherent light receiving device.
  • Coherent optical transmission technology has the advantages of large transmission capacity and long distance and is widely used.
  • the local oscillator light and signal light are simultaneously input to the mixing device for mixing, and the output light after mixing is converted into an electrical signal, which can be obtained through sampling, analog-to-digital conversion and digital signal processing.
  • the amplitude and phase information of the signal light so as to realize the decoding function.
  • the mixing device in the coherent optical receiver used in the industry needs to input the local oscillator light with a fixed polarization state. Since the data center network (DCN) and other networks cannot meet the special requirements for the polarization state of the local oscillator light, the mixing devices currently used in the industry cannot work normally, and finally the coherent optical transmission technology cannot be applied. In network application scenarios such as DCN, the general adaptability of coherent optical transmission technology is poor.
  • DCN data center network
  • an embodiment of the present application provides a coherent optical receiving device, which is used to solve the problem that the random change of the polarization state of the local oscillator light causes the receiver to fail to work normally.
  • an embodiment of the present application discloses a coherent light receiving device, and the coherent light receiving device includes:
  • the light splitting unit, the polarization control unit, the mixing unit and the combining unit, the polarization splitting unit is connected to the input end of the mixing unit, and the output end of the mixing unit is connected to the combining unit;
  • the light splitting unit is used to receive signal light and local oscillator light in any polarization mode, and decompose the signal light into multiple sub-signal lights, and split the local oscillator light into multiple sub-local oscillator lights;
  • the mixing unit is used to mix the sub-signal light and the sub-local oscillator light obtained above to obtain multiple mixed lights;
  • the synthesis unit is used for photoelectric conversion of multiple mixed lights to obtain multiple coherent electrical signals
  • the polarization control unit is used to control the polarization of the local oscillator light so that the first digital signal processor (DSP) obtains service data according to the multiple coherent electrical signals.
  • DSP digital signal processor
  • the polarization state of the local oscillator light changes randomly, and there are some polarization states that make the coherent light receiving device unable to work.
  • the coherent light receiving device provided in the first aspect of the application adjusts the polarization of the local oscillator light by introducing a polarization control unit to make the local oscillator light Avoid these polarization states that make the coherent light receiving device inoperable, so that the coherent light receiving device keeps working normally.
  • the light splitting unit receives signal light and local oscillator light in any polarization mode, and decomposes the signal light into multiple sub-signal lights, and decomposes the local oscillator light into multiple sub-local oscillator lights, which specifically includes:
  • the light splitting unit receives the signal light of any polarization mode, and decomposes the signal light into at least one first sub-signal light and at least one second sub-signal light, the first sub-signal light is in the first polarization mode, and the second sub-signal light
  • the second polarization mode; the beam splitting unit receives the local oscillator light of any polarization mode, and decomposes the local oscillator light into at least one first sub-local oscillator light and at least one second sub-local oscillator light, the first sub-local oscillator light Is the first polarization mode, and the second sub-local oscillator is the second polarization mode.
  • the mixing unit mixes the sub-signal light and the sub-local oscillator light to obtain multiple mixed light beams, which specifically include:
  • the mixing unit mixes each first sub-signal light with one of the first sub-local oscillator lights and mixes each second sub-signal light with one of the second sub-local oscillator lights to obtain multiple mixed lights .
  • the polarization control unit includes a plurality of first beam splitters BS, a phase modulator, a first photoelectric conversion module, and a signal processing module;
  • the multiple first BSs are used to couple out a part of the local oscillator light and split the beam to obtain multiple optical monitoring signals;
  • the first photoelectric conversion module is used to convert the optical monitoring signal into an electrical monitoring signal
  • the signal processing module is used for generating a feedback control electric signal according to the electric monitoring signal, and the feedback control electric signal is used for controlling the phase modulator to adjust the polarization of the local oscillator light so that the first DSP obtains the service data according to the multiple coherent electric signals.
  • the polarization splitting unit includes a first polarization splitting rotator PSR, a second PSR, a second BS, a third BS, a fourth BS, and a fifth BS;
  • the first PSR is used to decompose the signal light into the first signal light and the second signal light, the first signal light is in the first polarization mode, and the second signal light is in the second polarization mode;
  • the second BS is used to equally divide the first signal light into two first sub-signal lights
  • the third BS is used to equally divide the second signal light into two second sub-signal lights
  • the second PSR is used to decompose the signal light into the first local oscillation light and the second local oscillation light, the first local oscillation light is the first polarization mode, and the second local oscillation light is the second polarization mode;
  • the fourth BS is used to equally divide the first local oscillator light into two first sub-local oscillator lights
  • the fifth BS is used to equally divide the second local oscillator light into two second sub-local oscillator lights.
  • the polarization splitting design solution avoids the problem that the energy of the local oscillator light is concentrated in a certain polarization mode, and the service data cannot be obtained from the signal after the signal light and the local oscillator light are mixed.
  • the polarization control unit adjusts the polarization delay angle of the first local oscillator light and/or the second local oscillator light so that the first DSP obtains service data according to multiple coherent electrical signals.
  • the polarization splitting unit includes a first BS, a second BS, a first PSR, a second PSR, a third PSR, and a fourth PSR;
  • the first BS is used to equally divide the signal light into the first signal light and the second signal light;
  • the first PSR is used to decompose the first signal light into a first sub-signal light and a second sub-signal light;
  • the second PSR is used to decompose the second signal light into another first sub-signal light and another second sub-signal light;
  • the second BS is used to use the local oscillator light as the first local oscillator light and the second local oscillator light;
  • the third PSR is used to decompose the first signal light into a beam of first sub-local oscillator light and a beam of second sub-local oscillator light;
  • the fourth PSR is used to decompose the second signal light into another first sub-local oscillator light and another second sub-local oscillator light.
  • the BS first power splits the beam and then the PSR performs polarization splitting, which simplifies the design of the polarization splitting optical path.
  • the mixing unit includes at least one mixer, and the mixer includes a first beam splitter, a second beam splitter, a third beam splitter, a fourth beam splitter, and a 90-degree phase shifter,
  • the first beam splitter is used to equally divide a beam of first sub-signal light into two beams of first sub-beam sub-signal light
  • the third beam splitter is used for dividing a beam of first sub-local oscillator light into two beams of first sub-beam local oscillator;
  • the 90-degree phase shifter is used to shift the phase of one of the first beam splitter local oscillators by 90 degrees;
  • the second beam splitter is used to combine a first beam splitting sub-signal light and a first beam splitting sub-local oscillator light to output two mixed lights;
  • the fourth beam splitter is used to combine another first beam splitting sub-signal light and the first beam splitting sub-local oscillator light with a phase shift of 90 degrees to output the other two mixed beams.
  • the beam splitting unit includes a first fiber collimator, a second fiber collimator, a first lens, a second lens, a reflective component, and a rotator;
  • the light splitting unit receives the signal light and the local oscillator light of any polarization mode, and decomposes the signal light into multiple sub-signal lights, and decomposes the local oscillator light into multiple sub-local oscillator lights, including:
  • the first optical fiber collimator is used to receive and collimate the signal light
  • the second optical fiber collimator is used to receive and collimate the local oscillator light
  • the first lens is used to divide the signal light into a first sub-signal light and a second sub-signal light
  • the second lens is used to divide the local oscillator light into the first sub local oscillator light and the second sub local oscillator light, and the polarizer rotates the polarization of the second sub local oscillator light;
  • the reflection component includes a plurality of reflection mirrors, and the reflection component is used for reflecting the first sub-signal light, the second sub-signal light, the first sub-local oscillator light or the second sub-local oscillator light to the mixing unit.
  • the mixing unit includes a first mixer and a second mixer
  • the first mixer is used for mixing the first sub-signal light and the first sub-local oscillator light
  • the second mixer mixes the second sub-signal light and the polarization-rotated second sub-local oscillator light
  • the first mixer and the second mixer are also used to output multiple mixed beams.
  • the polarization control unit further includes a third PSR and a first polarization rotating beam combiner (PRC), and the output end of the PRC is connected to the second BS input end;
  • PRC polarization rotating beam combiner
  • the third PSR is used to receive the local vibration light and decompose the local vibration light into the third local vibration light and the fourth local vibration light, the third local vibration light is the first polarization mode, and the fourth local vibration light is the second polarization mode;
  • a plurality of third BSs respectively split the part of the local oscillator light from the third local oscillator light and the fourth local oscillator light and split the beams to obtain the multiple optical monitoring signals;
  • the photoelectric conversion module is used to convert optical monitoring signals into electrical monitoring signals
  • the signal processing module is used for the electrical monitoring signal to generate a feedback control electrical signal.
  • the feedback control electrical signal controls the phase modulator to adjust the phase of the third local oscillator light or the fourth local oscillator light to make the first DSP according to the Obtaining the service data from the multiple coherent electrical signals;
  • the first PRC is used to polarize and combine the third local oscillator light and the fourth local oscillator light after passing through the third BS.
  • the combining unit includes multiple second PRCs and multiple second photoelectric conversion modules; the second PRC is used to combine two of the multiple mixed light beams; multiple second photoelectric conversion modules; The conversion module is used for converting the multiple mixed light beams combined by the second PSR into multiple coherent electrical signals.
  • the synthesis unit includes a third photoelectric conversion module, and the third photoelectric conversion module includes multiple photodetectors PD, multiple electrical domain add-subtractors, multiple transimpedance amplifiers TIA, and multiple analog-to-digital converters.
  • ADC analog-to-digital converter
  • PD is used to convert multiple mixed beams into multiple mixed electrical signals
  • multiple electrical domain adders are used to synthesize multiple mixed electrical signals to obtain multiple coherent electrical signals
  • TIA is used to combine multiple coherent electrical signals Amplify
  • ADC is used to carry on the analog-to-digital conversion to a plurality of coherent electric signals.
  • the signal processing module includes a second DSP, a digital-to-analog converter DAC, and a power amplifier; the second DSP is used to generate a feedback control electrical signal according to the electrical monitoring signal; the DAC is used to perform digital-to-analog to the feedback control electrical signal Conversion; The power amplifier is used to amplify the power of the feedback control electrical signal that has undergone digital-to-analog conversion.
  • the coherent optical receiving device further includes a first DSP, and the first DSP is used to obtain service data based on multiple coherent electrical signals.
  • an embodiment of the present application discloses a polarization control method, which includes:
  • a feedback control electric signal is generated according to the multiple electric monitoring signals, and the feedback control electric signal is used to control the phase modulator to adjust the polarization of the local oscillator light so that the coherent light receiving device obtains service data.
  • an embodiment of the present application discloses an optical system, which includes an optical transmitting device, an optical fiber, and any coherent optical receiving device as in the first aspect.
  • the coherent optical receiving device receives a signal sent by the optical transmitting device through the optical fiber.
  • Light: The coherent light receiving device receives the local oscillator light or the coherent light receiving device generates the local oscillator light, which specifically includes:
  • the coherent optical receiving device receives the local oscillation light sent by the optical sending device through an optical fiber; or, the coherent optical receiving device generates the local oscillation light.
  • the coherent optical receiving device and optical system disclosed in the embodiments of the present application solve the problem that the random change of the polarization state of the local oscillator light causes the receiver to fail to work normally.
  • the coherent optical receiving device can maintain normal service data recovery. It further improves the stability of coherent light reception, reduces the difficulty and accuracy of polarization control, and saves costs.
  • Figure 1a shows a schematic diagram of possible application scenarios to which the embodiments of the present application are applicable
  • FIG. 1b is a schematic diagram of an existing coherent optical receiving device 1021 provided in this application.
  • FIG. 2 is a schematic diagram of a first embodiment of a coherent optical receiving device 20 disclosed in an embodiment of the application;
  • FIG. 3 is a schematic diagram of a second embodiment of a coherent optical receiving device disclosed in an embodiment of this application.
  • Fig. 4 is a schematic structural diagram of a mixer disclosed in an embodiment of the present application.
  • Figure 5 is a schematic diagram of the Bonga ball corresponding to the local oscillator
  • FIG. 6 is a flowchart of a polarization control method provided by an embodiment of the present application.
  • FIG. 7 is a schematic diagram of a third embodiment of a coherent optical receiving device disclosed in an embodiment of this application.
  • FIG. 8 is a schematic diagram of a fourth embodiment of a coherent optical receiving device disclosed in an embodiment of the application.
  • FIG. 9 is a schematic diagram of a fifth embodiment of a coherent optical receiving device disclosed in an embodiment of the application.
  • FIG. 10 is a schematic diagram of an optical system disclosed in an embodiment of this application.
  • the device forms and business scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present invention, and do not constitute a limitation on the technical solutions provided by the embodiments of the present invention.
  • a person of ordinary skill in the art knows that with the evolution of device forms and the emergence of new business scenarios, the technical solutions provided in the embodiments of the present application are equally applicable to similar technical problems.
  • Coherent light refers to an optical signal with a certain frequency and phase. Generally speaking, it can be a laser with spatial superposition and mutual interference characteristics generated by a laser.
  • Coherent optical transmission system also called coherent optical communication system
  • coherent optical communication system is a kind of optical fiber communication system. It uses a single frequency coherent light source, and uses multiple dimensions of light phase, frequency, amplitude and other parameters to carry more modulation information, so as to make full use of the fiber bandwidth and achieve ultra-high capacity transmission.
  • the basic structure of coherent optical transmission system includes: optical transmitter, optical fiber and optical receiver.
  • the optical reflector is used to modulate the signal that needs to be transmitted to the optical carrier to meet the requirements of optical transmission.
  • Direct modulation or external modulation can be used to modulate the amplitude, frequency and phase of the optical carrier.
  • the optical receiver is used for coherent detection of signal light, and improves the receiving sensitivity by detecting the difference between the local oscillator light and the signal light.
  • the signal light refers to the optical signal transmitted in the coherent optical transmission system
  • the local oscillator light refers to the laser light generated by the local oscillator on the receiver side.
  • the coherent optical receiving device and the optical signal demodulation device provided in the embodiments of the present application are devices applied in an optical receiver.
  • the coherent optical receiving device may be a front-end device in an optical receiver, or may be called a coherent receiving front-end,
  • the optical signal demodulation device may be an optical receiver.
  • the coherent optical receiving technical solution proposed in this application can be applied to different network scenarios, including but not limited to: backbone optical transmission network, optical access network, data center interconnection, short-distance optical interconnection, and wireless service forward/backhaul, etc.
  • the technical solution proposed in the present application may be used for the receiving-side equipment corresponding to the above-mentioned different networks, or an optical system including the receiving-side equipment.
  • Figure 1a shows a schematic diagram of possible application scenarios to which the embodiments of the present application are applicable.
  • FIG. 1a shows a homogenous coherent optical transmission system 100.
  • the system 100 includes a transmitting-side device 101 and a receiving-side device 102, and optical fibers 103a and 103b connecting the two devices.
  • the transmitting-side device 101 includes a data input 1011, a laser 1012, an optical splitter 1013, and a modulator 1014.
  • the light output by the laser 1012 is divided into two by the beam splitter 1013. One of them is modulated by the modulator 1014 to obtain the signal light loaded with service data, and the other is used as the local oscillator light.
  • the signal light and local oscillation light generated by the transmitting-side device 101 are transmitted to the receiving-end device 102 through the optical fibers 103a and 103b.
  • the receiving end device 102 includes a coherent optical receiving device 1021 and a digital signal processor (Digital Signal Processor, DSP) 1022.
  • the former receives signal light and local oscillator light to achieve coherent optical reception; the latter receives electrical signals output by the coherent optical receiver 1021 Perform processing to obtain business data. Both the signal light and the local oscillator light are generated by the transmitting side equipment. Therefore, the system 100 is called a homogenous coherent optical transmission system. It should be noted that the signal light and local oscillator light can also be transmitted through an optical fiber. It should also be noted that the DSP 1022 may also be located in the coherent optical receiving device 1021.
  • FIG. 1b is a schematic diagram of an existing coherent optical receiving device 1021 provided in this application.
  • the coherent optical receiving device 1021 includes a PSR10211, a PSR10212, a mixer 10213, a mixer 10214, and a coherent photoelectric processor 10215.
  • PSR Polarization beam splitter, polarization beam splitter
  • PSR10212 will input the original polarization
  • the polarization splitting of the vibration light obtains LO X and LO Y , that is, the linearly polarized light of the X polarization state and the linearly polarized light of the Y polarization state of the local vibration light.
  • the mixer 10213 mixes S X and LO Y to obtain 4 mixed light and inputs it to the coherent optoelectronic processor 10215.
  • the mixer 10214 mixes S Y and LO X to obtain 4 mixed light and inputs it to the coherent optoelectronic processor. 10215.
  • the coherent photoelectric processor 10215 performs coherent photoelectric processing on the 8 mixed lights to obtain multiple coherent electrical signals.
  • Signal light or local oscillator light has two polarization modes, TE and TM, which are also commonly referred to as X polarization state and Y polarization state.
  • the polarization state and the Y polarization state are orthogonal to each other. In other words, a beam with a single polarization state (polarization state Y) will become a beam with a polarization state of Y after the polarization state is rotated.
  • the optical signal is only polarized in the X polarization state or only in the Y polarization state, which is called linearly polarized light.
  • the existing coherent light receiving device usually mixes the X polarization state of the signal light with the Y polarization state of the local oscillator light and mixes the Y polarization state of the signal light with the X polarization state of the local oscillator light.
  • the existing coherent light receiving device can work normally.
  • the polarization states of the signal light and the local oscillator light are random, it is likely that the energy of the optical signal is concentrated in one polarization state, and there is almost no energy in the other polarization state.
  • the energy of the local oscillator light is concentrated in the X polarization state, and the Y polarization state of the local oscillator light has almost no energy. Then under the existing coherent light receiving device, the X polarization state of the signal light and the Y polarization state of the local oscillator light are If normal mixing is not possible, then the service data carried by the signal light X polarization state will be defective.
  • Using relatively expensive polarization-maintaining fiber under ideal conditions, can prevent the polarization state of the local oscillator light from being randomly deflected during transmission, so as to ensure that the coherent optical receiving device normally obtains service data.
  • the optical fiber will inevitably be squeezed, which will reduce the polarization-maintaining performance of the polarization-maintaining fiber, so that the performance of the coherent optical receiving device is reduced (that is, data receiving errors occur). Therefore, the use of polarization-maintaining fiber can solve the problem of random deflection of the polarization state of the local oscillator to a certain extent. However, this solution will increase the cost of the coherent optical transmission system, and the performance will be unstable.
  • the input of the coherent light receiving device is signal light and local oscillator light
  • the output is an electrical signal.
  • the output electrical signal includes service data
  • the final service data can be obtained by further processing the output electrical signal.
  • the coherent optical receiving device includes a DSP
  • its output is service data.
  • the coherent optical receiving device controls the phase of the local oscillator light accurately, so that two local oscillators with basically the same power are used for coherent reception related processing, which effectively avoids the random change of the polarization state of the local oscillator light and causes the receiver to fail to work normally.
  • the coherent optical transmission system can use conventional optical fibers (ie, non-polarization maintaining optical fibers) to realize normal coherent optical receiving.
  • FIG. 2 is a schematic diagram of a first embodiment of a coherent optical receiving device 20 disclosed in an embodiment of the application.
  • the coherent light receiving device 20 in the embodiment of the present application includes: a light splitting unit 201, a polarization control unit 202, a frequency mixing unit 203, and a combining unit 204.
  • the local oscillator light with any polarization state and the signal light with any polarization state are respectively input from the local oscillator optical port and the signal optical port of the coherent light receiving device 20; the beam splitting unit 201 decomposes the received local oscillator light to obtain multiple sub-local oscillators.
  • the light splitting unit 201 decomposes the received signal light to obtain multiple sub-signal lights, and the number of sub-local oscillator lights is the same as the number of sub-signal lights; the mixing unit 203 divides each of the multiple sub-signal lights with multiple sub-signal lights. One of the sub-local oscillator lights is mixed to obtain multiple mixed optical signals; the synthesis unit 204 photoelectrically converts the multiple mixed optical signals to output multiple coherent electrical signals; the polarization control unit 202 adjusts the local oscillator The polarization enables the DSP to obtain service data based on the above-mentioned multiple coherent electrical signals.
  • the polarization control unit 202 adjusting the polarization of the local oscillator light includes adjusting the phase of the local oscillator light.
  • the polarization states of the multiple sub-signal lights and multiple sub-local oscillator lights decomposed by the light splitting unit 201 are also random, not linearly polarized lights.
  • the light splitting unit 201 may be a polarization light splitting unit, then at this time:
  • the light splitting unit 201 decomposes the received local oscillator light to obtain multiple sub-local oscillator lights, and decomposes the received signal light to obtain multiple sub-signal lights, which specifically includes:
  • the signal light is decomposed into at least one first sub-signal light and at least one second sub-signal light
  • the local oscillation light is decomposed into at least one first sub-local oscillation light and at least one second sub-local oscillation light, wherein ,
  • the first sub-signal light and the first sub-local oscillation light are in the X polarization state
  • the second sub-local oscillation light and the second sub-signal light are in the Y polarization state.
  • the mixing unit 203 mixes each of the multiple sub-signal lights with one of the multiple sub-local oscillator lights to obtain multiple mixed optical signals, which specifically includes:
  • the mixing unit 203 mixes the first sub-signal light and the first sub-local oscillator light and mixes the second sub-signal light and the second sub-local oscillator light to obtain multiple mixed lights. That is, each first sub-signal light is mixed with a first sub-local oscillator light, and each second sub-signal light is mixed with a second sub-local oscillator light.
  • the combining unit 204 may first combine every two optical signals in the multiple mixed optical signals output by the mixing unit 203 after mixing into one beam to obtain multiple combined optical signals, and the number of combined optical signals It is half of the number of mixed optical signals, and then the multi-channel combined optical signal is photoelectrically converted to output multiple coherent electrical signals.
  • the polarization state of the local oscillator light changes randomly, and there are some polarization states that make the coherent light receiving device unable to work.
  • the coherent light receiving device provided in this embodiment of the application adjusts the polarization of the local oscillator light by introducing a polarization control unit to make the local oscillator light Avoid these polarization states that make the coherent light receiving device inoperable, so that the coherent light receiving device keeps working normally.
  • FIG. 3 is a schematic diagram of a second embodiment of a coherent optical receiving device disclosed in an embodiment of the application.
  • the coherent optical receiving device 30 in the embodiment of the present application includes: a signal light input port 301, a local oscillator light input port 302, a polarization beam splitting module 303, a power splitting module 304, a mixer 305, a mixing Frequency converter 2 306, mixer 3 307, mixer 4 308, polarization combining module 309, first photoelectric conversion module 310, second photoelectric conversion module 311, coupling beam splitting module 312, phase modulator 313, third A photoelectric conversion module 314, a signal processing module 315, and an ODSP (Optical Digital Signal Processing, optical digital signal processor) 316.
  • the phase modulator may be a general phase shifter (PS, Phase Shifter), or a half-wave plate, lens, and other elements capable of phase modulation.
  • the polarization beam splitting module, the power splitting module, and the polarization beam combining module described in this application are for the convenience of description and understanding, and mainly put together components with similar functions in the device; the photoelectric conversion module described in this application,
  • the coupling beam splitting module and the signal processing module are functional summaries of a certain range of components.
  • the division of the above-mentioned modules is to facilitate the understanding of the solution. In practice, there may be different module divisions.
  • the polarization splitting unit 201 in the embodiment of FIG. 2 includes the polarization splitting module 303 and the power splitting module 304 in this embodiment;
  • the polarization control unit 202 includes a coupling splitting module 312, a phase modulator 313, and a third photoelectric conversion module 314 And the signal processing module 315;
  • the mixing unit 203 includes a mixer 1 305, a mixer 2 306, a mixer 3 307, and a mixer 4 308;
  • the synthesis unit 204 includes a polarization beam combining module 309 and a first photoelectric conversion module 310 and the second photoelectric conversion module 311.
  • the signal light S is input from the signal light input port 301, and the PSR1 (Polarization Splitter and Rotator) in the polarization splitting module 303 polarizes the signal light S to obtain the first signal light S X and the second signal.
  • the local oscillator (LO) light is input from the local oscillator input port 302, and the PSR2 in the polarization beam splitting module 303 polarizes the signal light S to obtain the first local oscillator light LO X and the second local oscillator light LO Y.
  • the BS3 Beam Splitter, beam splitter
  • the first local oscillation light LO X and the second local oscillation light LO Y will be separated by BS5 and BS6 before entering BS3 and BS4, and a small part of the light will be separated for polarization control.
  • Mixer 1 305 receives F1 and F2 for mixing to obtain 4 channels of mixed light T1, T2, T3, T4, and mixer 2 306 receives F3 and F4 for mixing to obtain 4 channels of mixed light T5, T6, T7, T8, mixer 3 307 receives F5 and F6 for mixing to obtain 4 mixed lights T9, T10, T11, T12, and mixer 4 308 receives F7 and F8 for mixing to obtain 4 mixed lights T13, T14, T15, T16.
  • 16 beams of mixed light are obtained.
  • FIG. 4 is a schematic structural diagram of a mixer disclosed in an embodiment of the present application. Take the mixer 1 305 as an example.
  • the mixer includes a beam splitter 1 401, a beam splitter 2 402, a beam splitter 3 403, and a beam splitter 4 404 and 90 degree phase shifter 405, beam splitter 1 401 receives beam F1 and splits F1 to obtain two beams
  • the beam splitter 3 403 receives the beam F3 and splits the beam F3 to obtain two beams 90 degree phase shifter 405 for one of the beams Shift 90 degrees to get
  • the beam splitter 2 402 receives the light beam with Coupling and splitting to obtain (F1+F2)/2 and (F1-F2)/2
  • beam splitter 3 403 receives with Coupling and splitting to obtain mixed light (F1+j*F2)/2 and (F1-j*F2)/2
  • substituting F1 S X /2
  • mixer 2 306, mixer 3 307, and mixer 4 308 are similar to those of mixer 1 305, so the above-mentioned 16 mixing lights can be specifically as follows:
  • the mixing unit in the solution provided by the embodiment of this application has four mixers, and the following four situations are included in the mixing of signal light and local oscillator light: the X polarization state of the signal light and the local oscillator are included. Mixing of the X polarization state of the vibration light, mixing the X polarization state of the signal light and the Y polarization state of the local vibration light, mixing the Y polarization state of the signal light and the X polarization state of the local vibration light, and mixing the Y polarization state of the signal light and the Y polarization state of the signal light. The Y polarization state of the local oscillator is mixed.
  • Existing coherent light receiving devices usually only include two of the above four situations.
  • the X polarization state of the signal light is The Y polarization state of the vibrating light cannot be mixed normally, and the service data carried by the X polarization state of the signal light is missing.
  • the X polarization state of the signal light and the X polarization state of the local oscillator light can still be mixed normally. Therefore, the embodiment of the present application effectively avoids the problem that the random change of the polarization state of the local oscillator light causes the receiver to fail to work normally.
  • the polarization combining module 309 includes 8 PRCs (Polarization Rotator and Combiner), and each PRC mixes two of the 16 mixed lights to combine.
  • PRC1 combines the mixing lights T1 and T5
  • PRC2 combines the mixing lights T2 and T6
  • PRC3 combines the mixing lights T3 and T7
  • PRC4 combines the mixing lights T4 and T8.
  • the PRC1 combines the mixing lights T1 and T5, and so on, combines the xth output beam of the mixer 1 305 and the (x+a) output beam of the mixer 2 306 into one channel, and combines the mixed light beams.
  • the x-th output beam in the frequency converter 3 307 and the (x+a)-th output beam in the mixer 4 308 are combined into one channel.
  • a is the number of beams output by the PRC.
  • PRC1 Take PRC1 as an example.
  • PRC1 combines T1 and T5. There will be loss in the process of combining. Here, the loss of both T1 and T5 is calculated by half, then the combined beam
  • the light beams E1 and E2 are respectively received by PD1 (Photonic detector) and PD2 in the first photoelectric conversion module 310 to obtain electrical domain signals:
  • the coherent electrical signal I 2, I output by the adder-subtractor 3 is:
  • the coherent electrical signal I 2, Q output by the adder-subtractor 4 is:
  • Operation real means taking the real part
  • operation imag means taking the imaginary part
  • the four coherent electrical signals of I 1,I , I 1,Q , I 2,I , I 2,Q are amplified by their respective trans-impedance amplifiers (TIA) before being amplified by analog digital converters (analog digital converters). , ADC) After sampling, send it to ODSP316 to process and restore business data.
  • the coherent optical receiving device 30 may include an ODSP316, and the ODSP316 may also be located outside the coherent optical receiving device 30.
  • ODSP316 recovers to obtain service data based on the coherent electrical signal.
  • polarization rotation angle or polarization delay angle of the local oscillator light is at a specific value, ODSP316 cannot retrieve the service data based on the coherent electrical signal.
  • the MIMO algorithm in ODSP316 can be used from two complex signals Recover business data.
  • the intrinsic light is linearly polarized light at the emitting end, which can be written as
  • the intrinsic light arriving at the receiving end after being transmitted through the fiber channel (through the Jones matrix) can be expressed as
  • ⁇ is the polarization rotation angle of the local vibrating light, It is the polarization delay angle of the local oscillator. Bring this formula into the M matrix to get:
  • a polarization control unit is introduced to adjust the polarization of the local oscillator light so that the ODSP 316 obtains service data according to the multiple coherent electrical signals.
  • a phase modulator 313 is added to one of the first local oscillation light LOX and the second local oscillation light LOY after the local oscillation light passes through the PSR2.
  • the phase modulator 313 is placed on the second LOY branch of the local oscillator light.
  • the phase modulator 313 can also be placed on the first local oscillator LOX branch. Adjust the polarization delay angle of the first local oscillator light or the second local oscillator light by controlling the phase modulator It is possible to achieve a state where the control matrix M is always healthy and reversible.
  • phase modulator 313 Set the polarization delay angle of the phase modulator 313 to the first local oscillator light or the second local oscillator light Introduce phase
  • the matrix M can be rewritten as:
  • FIG. 5 is a schematic diagram of the Bonga ball corresponding to the local oscillator.
  • the polarization rotation angle ⁇ of the local oscillator light and the polarization delay angle of the local oscillator light After the value is traversed, the polarization state of the local oscillator light falls on the spherical surface of the Poinka sphere.
  • the polarization delay angle of the first local oscillator light or the second local oscillator light through the phase modulator 313 Introduce phase The adjusted local oscillator light falls within the black interval on the spherical surface, and the M matrix reaches a healthy and reversible state.
  • the polarization control unit 202 only needs to bypass the white interval of the local oscillator light randomly disturbed on the spherical surface and fall on the black interval, so that the ODSP316 can recover the service data according to the coherent electrical signal, and the coherent light receiving device can work normally. Reduce the difficulty of feedback control. In the existing coherent light receiving device, it is often necessary to control the local oscillator light randomly disturbed on the spherical surface at one point or a small area, which is difficult to control.
  • the polarization control provided by the embodiments of the present application reduces the difficulty and accuracy of polarization control, and saves design costs.
  • FIG. 6 is a flowchart of a polarization control method provided by an embodiment of the present application. Specifically, the control process of the polarization control unit 202 is as follows:
  • Step 601 Split a part of the local oscillator light, and split this part of the local oscillator light to obtain multiple optical monitoring signals;
  • the coupling beam splitting module 312 includes multiple BSs. Among them, BS5 and BS6 each couple out a small part of the local oscillator light. The two beams are divided into 4 optical monitoring signals by BS7 and BS8 respectively, and two of them pass through BS9 coupled and added to obtain the following 3 channels of mixed light:
  • Step 602 Convert multiple optical monitoring signals into multiple electrical monitoring signals
  • the above three channels of mixed light are then received by PD9, PD10, and PD11 in the third photoelectric conversion module 314, amplified by TIA5, TIA6, and TIA7, and sampled by ADC5, ADC6, and ADC7 to obtain three electrical monitoring signals:
  • Step 603 Generate a feedback control electrical signal according to the multiple electrical monitoring signals.
  • the feedback control electrical signal is used to control the phase modulator to adjust the polarization of the local oscillator light so that the ODSP316 obtains service data based on the multiple coherent electrical signals.
  • the signal processing module 315 monitors the energy of the electrical monitoring signal:
  • the phase modulator 313 When the energy of I 10 and I 30 are close, the phase modulator 313 needs to be activated to control the polarization of the local oscillator light. At this time, the signal processing module 315 generates a feedback control signal to adjust the phase modulator 313. When the phase modulator 313 is adjusted so that ( The energy of I 2 -I 1 -I 3 ) becomes larger, and it can be determined that the current M matrix is invertible and the coherent light receiving device can work normally. Optionally, the feedback control electrical signal controls the phase modulator 313 to adjust the phase of the first local oscillator light or the second local oscillator light so that the ODSP 316 obtains service data according to the multiple coherent electrical signals.
  • adjusting the phase of the first local oscillation light or the second local oscillation light includes adjusting the polarization delay angle of the first local oscillation light or the second local oscillation light.
  • the phase modulator 313 introduces the phase of the first local oscillation light or the second local oscillation light phase modulator 313 when When approaching 90 degrees, that is, the polarization delay angle of the first local oscillator light or the second local oscillator light Plus the phase introduced by the phase modulator 313 After approaching 90 degrees, it is considered that the coherent light receiving device can work normally at this time.
  • the signal processing module 315 includes a DSP3151, a DAC3152 (digital-to-analog converter, digital-to-analog converter), and a power amplifier 3153.
  • the DSP3151 is used to generate a feedback control electrical signal according to the electrical monitoring signal, and the feedback control electrical signal is used to control the phase modulator to adjust the polarization of the local oscillator light so that the ODSP316 obtains service data based on multiple coherent electrical signals.
  • DAC3152 is used for digital-to-analog conversion of feedback control electrical signals.
  • the power amplifier 3153 is used to amplify the power of the feedback control electrical signal that has undergone digital-to-analog conversion.
  • BS5 and BS6 can select a 90:10 or 95:5 splitter, that is, 10% of the local oscillator light or 5% of the local oscillator light on each branch is coupled out for polarization control.
  • the coherent optical receiving device disclosed in the embodiments of the present application solves the problem that the random change of the polarization state of the local oscillator light causes the receiver to fail to work normally.
  • the coherent optical receiving device can maintain normal recovery of service data, and further improve The stability of coherent light reception is improved, and the polarization control unit is simplified, which reduces the difficulty and accuracy of polarization control and saves costs.
  • the 90-degree phase shift or the 90-degree rotation of the polarization state mentioned in this application may also be a 270 degree phase shift or 270-degree rotation of the polarization state. It should be understood that the phase shift or deflection has the same technical effect as the 90-degree phase shift or 90-degree rotation of the polarization state. Any attitude is acceptable. It should be noted that the aforementioned degree of rotation may have a small deviation due to actual device process limitations and other reasons. It should be understood that the 90-degree phase shift or the 90-degree rotation of the polarization state mentioned in this application includes such a rotation of approximately 90 degrees or 270 degrees.
  • the PSR mentioned in the embodiments of this application can be replaced with a combination of PBS (Polarization Beam Splitter) and PR (Polarization Rotator) connection
  • PRC can be replaced with PBC (Polarization Beam Combiner).
  • PBC Polarization Beam Combiner
  • PSR with a combination of PBS and PR connection
  • PRC with a combination of PBC and PR belongs to a simple structure modification and also belongs to the technical solution protected by the present application.
  • the optical splitter may be a waveguide coupler or a multimode interferometer (MMI) coupler.
  • MMI multimode interferometer
  • FIG. 7 is a schematic diagram of a third embodiment of a coherent optical receiving device disclosed in an embodiment of the application.
  • the coherent optical receiving device 70 includes: signal light input port 301, local oscillator light input port 302, polarization beam splitting module 303, power sharing module 304, mixer 1 305, mixer 2 306 , Mixer 3 307, mixer 4 308, photoelectric conversion module 701, coupling beam splitting module 312, phase modulator 313, third photoelectric conversion module 314, signal processing module 315 and ODSP316.
  • the signal processing module 315 is the same as that shown in FIG.
  • FIG. 7 The difference between Fig. 7 and Fig. 3 is mainly the photoelectric conversion module 701 that processes the 16 beams of mixed light output by the mixing unit, mixer 1 305, mixer 2 306, mixer 3 307, mixer 4 Refer to Figure 3 for the structure before 308.
  • Mixer 1 305, Mixer 2 306, Mixer 3 307, Mixer 4 308 output the 16 mixed light T1 ⁇ T16, firstly convert PD1 ⁇ PD16 into electrical signal, and then pass the adder and subtractor After addition and subtraction, multiple coherent electrical signals are obtained.
  • T1, T2, T5, and T6 get 4 channels of mixed electrical signals after PD detection:
  • the coherent electrical signal I 2, I output by the adder-subtractor 8 is:
  • the coherent electrical signals I 2, Q output by the adder-subtractor 10 are:
  • the order of the output mixing light of the mixer 2 306 and the mixer 4 308 can be reversed to reduce the light path crossing after the mixer.
  • the coherent optical receiving device does not adopt the optical path polarization beam combination scheme for the mixed light output by the mixer, but directly adds and subtracts by adding an adder and subtractor to avoid the coupling loss caused by polarization beam combination. , The insertion loss is smaller.
  • FIG. 8 is a schematic diagram of a fourth embodiment of a coherent optical receiving device disclosed in an embodiment of the application.
  • the coherent optical receiving device 80 includes BS1 801, BS2 802, polarization beam splitting module 803, PSR4 804, PSR6 805, and polarization control module 806; it also includes signal light input port 301, local oscillator light input port 302. Mixer 1 305, Mixer 2 306, Mixer 3 307, Mixer 4 308, Phase modulator 313, ODSP 316, please refer to the relevant description in FIG. 3.
  • the polarization beam splitting module 803 includes 4 PSRs: PSR1, PSR2, PSR3 and PSR4. The main difference between the embodiment shown in FIG. 8 and FIG. 3 is that the optical path is simplified for the polarization splitting of the signal light and the local oscillator light.
  • the signal light S is input from the signal light input port 301.
  • the PSR1 in the polarization beam splitting module 803 polarizes the first signal light to obtain a first signal light.
  • Sub-signal light F1 and a second sub-signal light F7 PSR3 polarizes the second signal light to obtain another first sub-signal light F3 and a second sub-signal light F5, wherein the first sub-signal light The light is in the X polarization state, and the second sub-signal light is in the Y polarization state.
  • the local oscillator light LO is input from the local oscillator light input port 302, and first passes through the PSR5 804 polarization beam splitting to obtain the third local oscillator light and the fourth local oscillator light.
  • the third local oscillator light is in the X polarization state
  • the fourth local oscillator light is in the Y polarization state.
  • BS5 and BS6 respectively couple a part of the local oscillator light and input it to the polarization control module 806 for polarization control.
  • an optical monitoring signal is obtained.
  • the optical monitoring signal is converted into an electrical monitoring signal, and feedback control is generated according to the electrical monitoring signal.
  • the signal control phase modulator 313 adjusts the phase of the fourth local oscillator light.
  • the specific principle of the polarization control module 806 can be referred to the related description in FIG. 3.
  • PRC6 805 combines the third local oscillator light and the fourth local oscillator light passing through BS5 and BS6 by polarization and input to BS2 802.
  • the polarization control module 806 may include the BS7, BS8, BS9 and the third photoelectric conversion module 314, the signal processing module 315, and the ODSP 316 in the coupling beam splitting module 312 in the embodiment of FIG. 3.
  • BS2 802 splits the local oscillator optical power to obtain the first local oscillator light and the second local oscillator light
  • the PSR2 in the polarization beam splitting module 803 polarizes the first local oscillator light to obtain a first sub-local oscillator light F2 And a beam of second local oscillator light F6, PSR4 polarizes the second local oscillator light to obtain another beam of first local oscillator light F4 and a beam of second local oscillator light F8, among which, the first sub local oscillator The vibration light is in the X polarization state, and the second sub-local vibration light is in the Y polarization state.
  • the photoelectric conversion module 701 of FIG. 7 can also be connected; or the polarization beam combining module 309 in FIG. 3 can be connected, and then the first photoelectric conversion module 310 and the second photoelectric conversion module 311 can be connected.
  • the polarization splitting scheme of FIG. 3 of the present application first performs BS power splitting after PSR polarization splitting, while the polarization splitting scheme of FIG. 8 of the present application first performs BS power splitting and then performs PSR polarization splitting.
  • the signal light may also adopt the polarization splitting scheme in the embodiment of FIG. 3, and the local oscillator light may adopt the polarization splitting scheme in the embodiment of FIG. 8; or, it may also be the signal light.
  • the polarization splitting scheme in the embodiment of FIG. 8 is adopted, and the local vibration light uses the polarization splitting scheme in the embodiment of FIG. 3.
  • the embodiments of the present application only show possible combinations. It is suggested that on the basis of the embodiments of the present application, easily conceivable combinations of the structures of the embodiments of the present application should also be included in the protection scope of the present application.
  • FIG. 9 is a schematic diagram of a fifth embodiment of a coherent optical receiving device disclosed in an embodiment of the application.
  • the coherent light receiving device 90 includes: a fiber collimator 901, a fiber collimator 902, a lens 1 903, a lens 1 904, a reflection component 1 905, a reflection component 2 906, a rotator 907, a hybrid
  • the frequency converter 908 and the mixer 909 in addition, it also includes a signal light input port 301, a local oscillator light input port 302, a phase modulator 313, and a polarization control module 806. Please refer to the related descriptions in FIGS. 3 and 8.
  • the signal light After the signal light is collimated by the fiber collimator 901, it is input to the lens 1 903, and the lens 1 903 decomposes the signal light into the first signal light and the second signal light; the local oscillation light is collimated by the fiber collimator 902 and then input To the lens 2 904, the lens 2 904 decomposes the local oscillation light into the first local oscillation light and the second local oscillation light, and the second local oscillation light enters the mixer 909 after being rotated by the polarizer 907.
  • the mixer 908 mixes the first signal light and the first local oscillation light, and the mixer 909 mixes the second signal light and the second local oscillation light.
  • the mixer 908 and the mixer 909 may be spatial mixers.
  • the reflective component 1 905 can reflect the second signal light to input the second signal light to the mixer 908, and the reflective component 2 906 can reflect the second local oscillator light to input the second local oscillator light. To the mixer 907.
  • the rotator may be a 90-degree polarization rotator.
  • FIG. 10 is a schematic diagram of an optical system disclosed in an embodiment of this application.
  • the optical system 100 includes: an optical transmitting device 1001, an optical fiber 1002, and a coherent optical receiving device 1003.
  • the coherent optical receiving device 1003 receives the signal light sent by the optical transmitting device 1001 through the optical fiber 1002; the coherent optical receiving device 1003 receives local oscillator light through the optical fiber 1002 or the coherent optical receiving device 1003 generates local oscillator light.
  • the coherent optical receiving device 1003 may be any coherent optical receiving device in the above-mentioned embodiments.

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Abstract

本申请涉及光通信领域，尤其涉及一种相干光接收装置和采用相干光接收装置的光***。该相干光接收装置包括分光单元、偏振控制单元、混频单元和合成单元。偏振分光单元与混频单元的输入端连接，混频单元的输出端与合成单元连接。分光单元，用于接收任意偏振模式的信号光和本振光，并将信号光分解为多束子信号光，将本振光分解为多束子本振光。混频单元，用于将子信号光和所述子本振光进行混频，得到多束混频光。合成单元，用于将多束混频光进行光电转换得到输出多个相干电信号。偏振控制单元，用于控制上述本振光的偏振使数字信号处理器根据上述多个相干电信号得到业务数据。

Description

相干光接收装置和采用相干光接收装置的光***
本申请要求于2019年12月31日提交中国国家知识产权局、申请号为201911414636.X、发明名称为“相干光接收装置和采用相干光接收装置的光***”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及光通信领域，尤其涉及一种相干光接收装置和采用相干光接收装置的光***。
背景技术
相干光传输技术具有传输容量大、距离远等优点被广泛应用。在相干光通信***的接收端，将本振光和信号光同时输入混频装置进行混频，将混频后的输出光转换为电信号，并通过采样、模数转换和数字信号处理可以得到信号光的振幅和相位信息，从而实现解码功能。
目前，业界使用的相干光接收机中的混频装置需要输入偏振态固定的本振光。由于在数据中心网络(data center network，DCN)等网络中无法满足此种对本振光的偏振态的特殊要求，造成业界目前使用的混频装置无法正常工作，最终使得相干光传输技术无法应用于DCN等网络应用场景中，造成相干光传输技术的普遍适应性较差。
发明内容
鉴于此，本申请实施例提供了一种相干光接收装置，用于解决本振光的偏振态随机变化导致接收机无法正常工作的问题。
第一方面，本申请实施例公开了一种相干光接收装置，该相干光接收装置包括：
分光单元、偏振控制单元、混频单元和合成单元，偏振分光单元与混频单元的输入端连接，混频单元的输出端与合成单元连接；
分光单元，用于接收任意偏振模式的信号光和本振光，并将信号光分解为多束子信号光，将本振光分解为多束子本振光；
混频单元，用于将上述得到的子信号光和子本振光进行混频，得到多束混频光；
合成单元，用于将多束混频光进行光电转换得到输出多个相干电信号；
偏振控制单元，用于控制所述本振光的偏振使第一数字信号处理器(DSP)根据上述多个相干电信号得到业务数据。
本振光的偏振态随机变化，会存在一些偏振态使相干光接收装置不能工作，本申请第一方面提供的相干光接收装置通过引入偏振控制单元来调节本振光的偏振，使本振光避开这些使相干光接收装置不能工作的偏振态，从而使相干光接收装置保持正常工作。
一种可能的设计中，分光单元接收任意偏振模式的信号光和本振光，并将信号光分解为多束子信号光，将本振光分解为多束子本振光，具体包括：
分光单元接收任意偏振模式的信号光，并将信号光分解为至少一束第一子信号光和至少一束第二子信号光，第一子信号光为第一偏振模式，第二子信号光为第二偏振模式；分光单元接收任意偏振模式的本振光，并将本振光分解为至少一束第一子本振光和至少一束第二子本振光，第一子本振光为所述第一偏振模式，第二子本振光为所述第二偏振模式。
一种可能的设计中，混频单元将子信号光和所述子本振光进行混频得到多束混频光，具 体包括：
混频单元将每个第一子信号光和其中一个第一子本振光进行混频以及将每个第二子信号光与其中一个第二子本振光进行混频得到多束混频光。
一种可能的设计中，偏振控制单元包括多个第一分束器BS、相位调制器、第一光电转换模块和信号处理模块；
多个第一BS用于耦合出一部分本振光并分束得到多束光监控信号；
第一光电转换模块用于将光监控信号转换成电监控信号；
信号处理模块用于根据电监控信号生成反馈控制电信号，该反馈控制电信号用于控制相位调制器以调节本振光的偏振使第一DSP根据多个相干电信号得到业务数据。
一种可能的设计中，偏振分光单元包括第一偏振分束旋转器PSR、第二PSR、第二BS、第三BS、第四BS和第五BS；
第一PSR用于将信号光分解为第一信号光和第二信号光，第一信号光为第一偏振模式，第二信号光为第二偏振模式；
第二BS用于将第一信号光均分为两束第一子信号光；
第三BS用于将第二信号光均分为两束第二子信号光；
第二PSR用于将信号光分解为第一本振光和第二本振光，第一本振光为第一偏振模式，第二本振光为第二偏振模式；
第四BS用于将第一本振光均分为两束第一子本振光；
第五BS用于将第二本振光均分为两束第二子本振光。
该偏振分光设计方案避免了本振光的能量集中在某一种偏振模式下造成的无法从信号光和本振光混频后的信号中获取业务数据的问题。
一种可能的设计中，偏振控制单元调节上述第一本振光和/或第二本振光的偏振延迟角使第一DSP根据多个相干电信号获取业务数据。
一种可能的设计中，偏振分光单元包括第一BS、第二BS、第一PSR、第二PSR、第三PSR和第四PSR；
所述第一BS用于将信号光均分为第一信号光和第二信号光；
所述第一PSR用于将第一信号光分解为一束第一子信号光和一束第二子信号光；
所述第二PSR用于将第二信号光分解为另一束第一子信号光和另一束第二子信号光；
所述第二BS用于将本振光为第一本振光和第二本振光；
所述第三PSR用于将第一信号光分解为一束第一子本振光和一束第二子本振光；
所述第四PSR用于将第二信号光分解为另一束第一子本振光和另一束第二子本振光。
该偏振分光设计方案，通过BS先功率分束再通过PSR进行偏振分束，简化偏振分光光路设计。
一种可能的设计中，混频单元包括至少一个混频器，混频器包括第一分光器、第二分光器、第三分光器、第四分光器和90度移相器，
第一分光器用于将一束第一子信号光均分为两束第一分束子信号光，
第三分光器用于将一束第一子本振光均分为两束第一分束子本振光；
90度移相器用于将其中一束所述第一分束子本振光移相90度；
第二分光器用于将一束第一分束子信号光和一束第一分束子本振光合成后输出两束混频光；
第四分光器用于将另一束第一分束子信号光和经过移相90度的第一分束子本振光合成后输出另两束混频光。
一种可能的设计中，分光单元包括第一光纤准直器、第二光纤准直器、第一透镜、第二透镜、反射组件和旋偏器；
分光单元接收任意偏振模式的信号光和本振光，并将信号光分解为多束子信号光，将本振光分解为多束子本振光，包括：
第一光纤准直器用于接收所述信号光并准直；
第二光纤准直器用于接收所述本振光并准直；
第一透镜用于将信号光分成第一子信号光和第二子信号光；
第二透镜用于将本振光分成第一子本振光和第二子本振光，旋偏器将第二子本振光偏振旋转；
反射组件包括多个反射镜，反射组件用于将第一子信号光、第二子信号光、第一子本振光或第二子本振光反射到混频单元。
一种可能的设计中，混频单元包括第一混频器和第二混频器；
第一混频器用于将第一子信号光和第一子本振光进行混频，以及第二混频器将第二子信号光和经过偏振旋转的第二子本振光进行混频；
第一混频器和第二混频器，还用于输出多束混频光。
一种可能的设计中，偏振控制单元还包括第三PSR和第一偏振旋转合束器(PRC)，PRC的输出端连接第二BS输入端；
第三PSR用于接收本振光并将本振光分解为第三本振光和第四本振光，第三本振光为第一偏振模式，第四本振光为第二偏振模式；
多个第三BS分别从所述第三本振光和所述第四本振光分出所述一部分本振光并分束得到所述多束光监控信号；
光电转换模块用于将光监控信号转换成电监控信号；
信号处理模块用于电监控信号生成反馈控制电信号，该反馈控制电信号控制所述相位调制器以调节所述第三本振光或第四本振光的相位使所述第一DSP根据所述多个相干电信号得到所述业务数据；
第一PRC用于将经过第三BS后的第三本振光和第四本振光进行偏振合束。
一种可能的设计中，合成单元包括多个第二PRC、多个第二光电转换模块；第二PRC用于将多束混频光中的其中两束混频光合束；多个第二光电转换模块用于将多个经过第二PSR合束后的混频光转换成多个相干电信号。
一种可能的设计中，合成单元包括第三光电转换模块，第三光电转换模块包括多个光电探测器PD、多个电域加减器、多个跨阻放大器TIA和多个模数转换器ADC；
PD用于将多束混频光转换成多束混频电信号，多个电域加减器用于将多束混频电信号合成得到多个相干电信号，TIA用于将多个相干电信号放大，ADC用于对多个相干电信号进行模数转换。
一种可能的设计中，信号处理模块包括第二DSP、数模转换器DAC和功率放大器；第二DSP用于根据电监控信号生成反馈控制电信号；DAC用于对反馈控制电信号进行数模转换；功率放大器用于对经过数模转换的反馈控制电信号进行功率放大。
一种可能的设计中，相干光接收装置还包括第一DSP，第一DSP用于根据多个相干电信 号得到业务数据。
第二方面，本申请实施例公开了一种偏振控制方法，该方法包括：
分出一部分本振光，并将这部分本振光分束得到多束光监控信号；
将多束光监控信号转换为多束电监控信号；
根据多束电监控信号生成反馈控制电信号，该反馈控制电信号用于控制相位调制器以调节本振光的偏振使相干光接收装置得到业务数据。
第三方面，本申请实施例公开了一种光***，该***包括光发送设备、光纤和如第一方面中任意一种相干光接收设备，相干光接收设备通过光纤接收光发送设备发送的信号光；相干光接收设备接收本振光或者相干光接收设备产生本振光，具体包括：
相干光接收设备通过光纤接收光发送设备发送的本振光；或者，所述相干光接收设备产生本振光。
综上，本申请实施例公开的相干光接收装置和光***解决了本振光的偏振态随机变化导致接收机无法正常工作的难题，通过引入偏振控制使相干光接收装置可以保持正常恢复业务数据，进一步提升了相干光接收的稳定性，降低了偏振控制的难度和精度，节约成本。
附图说明
为了更清楚地说明本申请的实施例或现有技术中的技术方案，下面将对描述背景技术和实施例时所使用的附图作简单的介绍。显而易见地，下面附图中描述的仅仅是本申请的一部分实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图和描述得到其他的附图或实施例，而本申请旨在涵盖所有这些衍生的附图或实施例。
图1a给出了本申请实施例适用的可能的应用场景示意图；
图1b是本申请给出一种现有的相干光接收装置1021示意图；
图2为本申请实施例公开的相干光接收装置20的第一实施例示意图；
图3为本申请实施例公开的相干光接收装置的第二实施例示意图；
图4是本申请实施例公开的一种混频器的结构示意图；
图5是本振光对应的邦加球示意图；
图6是本申请实施例提供的偏振控制方法流程图；
图7为本申请实施例公开的相干光接收装置的第三实施例示意图；
图8为本申请实施例公开的相干光接收装置的第四实施例示意图。
图9为本申请实施例公开的相干光接收装置的第五实施例示意图。
图10为本申请实施例公开的一种光***的示意图。
具体实施方式
本申请实施例描述的设备形态以及业务场景是为了更加清楚地说明本发明实施例的技术方案，并不构成对本发明实施例提供的技术方案的限制。本领域普通技术人员可知，随着设备形态的演变和新业务场景的出现，本申请实施例提供的技术方案对于类似的技术问题同样适用。
以下，对本申请实施例中的部分用语进行解释说明，以便于本领域技术人员理解。
1)相干光，是指有确定的频率和相位的光信号。一般来说，可以为由激光器产生的具有空间叠加、相互干涉特性的激光。
2)相干光传输***，也称为相干光通信***，是一种光纤通信***。它采用单一频率的相干光源，利用光的相位、频率、幅度等多个维度的参量来承载更多的调制信息，以充分利用光纤带宽，实现超高容量的传输。相干光传输***的基本结构包括：光发送机、光纤和光接收机等。其中，光反射机，用于将需要外传的信号调制到光载波上，以适应光传输的要求。可以采用直接调制或外调制的方式，对光载波进行幅度、频率和相位调制。光接收机，用于对信号光进行相干检测，通过检测本振光和信号光的差来提高接收的灵敏度。这里，信号光是指相干光传输***中传输的光信号，本振光是指在接收机一侧由本地振荡器产生的激光。
本申请实施例中提供的相干光接收装置和光信号解调装置为应用在光接收机中的装置，该相干光接收装置可以为光接收机中的前端设备，也可以被称为相干接收前端，光信号解调装置可以为光接收机。
需要理解的是，在下文的描述中，“第一”、“第二”等词汇，仅用于区分描述的目的，而不能理解为指示或暗示相对重要性，也不能理解为指示或暗示顺序。本申请中出现的术语“和/或”，可以是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本申请中字符“/”，一般表示前后关联对象是一种“或”的关系。
本申请提出的相干光接收技术方案可适用于不同网络场景，包括但不限于：骨干光传输网络、光接入网络、数据中心互连、短距离光互联和无线业务前传/回传等。具体地，本申请提出的技术方案可以用于上述不同网络对应的接收侧设备，或者包括接收侧设备的光***。
图1a给出了本申请实施例适用的可能的应用场景示意图。
图1a所示为一种同源相干光传输***100。该***100包括发送侧设备101和接收侧设备102，以及连接这两个设备的光纤103a和103b。发送侧设备101包括数据输入1011、激光器1012、分光器1013和调制器1014。激光器1012输出的光被分光器1013一分为二。其中一个通过调制器1014调制得到加载了业务数据的信号光，另外一个作为本振光。发送侧设备101产生的信号光和本振光通过光纤103a和103b传输到接收端设备102。接收端设备102包括相干光接收装置1021和数字信号处理器(Digital Signal Processor，DSP)1022，前者接收信号光和本振光，实现相干光接收；后者对相干光接收装置1021输出的电信号进行处理从而获得业务数据。信号光和本振光都由发送侧设备产生。因此，***100被称为同源相干光传输***。需要说明的是，信号光和本振光也可以通过一根光纤来传递。还需要说明的是，DSP 1022也可能位于相干光接收装置1021中。
图1b是本申请给出一种现有的相干光接收装置1021示意图。
如图1b所示，该相干光接收装置1021包括PSR10211、PSR10212、混频器10213、混频器10214和相干光电处理器10215。PSR(Polarization beam splitter，偏振分束器)10211将输入的信号光偏振分束得到S X和S Y，即信号光的X偏振态线偏振光和Y偏振态线偏振光；PSR10212将输入的本振光偏振分束得到LO X和LO Y，即本振光的X偏振态线偏振光和Y偏振态线偏振光。混频器10213将S X和LO Y混频得到4束混频光输入到相干光电处理器10215，混频器10214将S Y和LO X混频得到4束混频光输入到相干光电处理器10215。相干光电处理器10215对8束混频光进行相干光电处理得到多个相干电信号。
信号光或本振光具有TE、TM两个偏振模式，也通常被称为X偏振态和Y偏振态。偏振态和Y偏振态互为正交。也就是说，一个为单一偏振态(偏振态Y)的光束通过偏振态旋转 后，会变成一个偏振态为Y的光束。光信号只在X偏振态偏振或只在Y偏振态偏振，称为线偏振光。
现有的相干光接收装置通常将信号光的X偏振态与本振光的Y偏振态混频以及将信号光的Y偏振态与本振光的X偏振态混频。当信号光与本振光的偏振态都是固定，通常现有相干光接收装置可以正常工作。但当信号光与本振光的偏振态都是随机的时候，很可能会出现光信号的能量集中在某一偏振态上，另一偏振态上几乎没有能量。例如本振光的能量集中在X偏振态上，本振光的Y偏振态几乎没有能量，那么在现有的相干光接收装置下，信号光的X偏振态与本振光的Y偏振态就没法进行正常的混频，那么信号光X偏振态所携带业务数据就缺损了。采用价格较为昂贵的保偏光纤，在理想情况下，可以防止本振光在传输中发生偏振态随机偏转，以保证相干光接收装置正常获取业务数据。但是，在现网中，光纤不可避免地会遭受挤压，从而会使保偏光纤的保偏性能降低，以至于相干光接收装置的性能降低(即发生数据接收错误)。因此，采用保偏光纤虽然可以在一定程度上解决本振光发生偏振态随机偏转的问题。但是，这种解决方案会增加相干光传输***的成本，且性能不稳定。
为了解决上述提到的现有技术问题，本申请提供了一种新的相干光接收装置。其中，相干光接收装置的输入为信号光和本振光，输出为电信号。该输出的电信号中包括了业务数据，可以通过进一步地处理该输出的电信号来获取最终的业务数据。可选地，如果相干光接收装置包括了DSP，则其输出为业务数据。该相干光接收装置通过对本振光较为精确的相位控制，使得两束功率基本相同的本振光用于相干接收相关的处理，有效地避免了本振光的偏振态随机变化导致接收机无法正常工作的问题。通过采用该相干光接收装置，相干光传输***可以采用常规的光纤(即非保偏光纤)来实现正常的相干光接收。
图2为本申请实施例公开的相干光接收装置20的第一实施例示意图。
如图2所示，本申请实施例中相干光接收装置20包括：分光单元201、偏振控制单元202、混频单元203和合成单元204。首先，偏振态任意的本振光和偏振态任意的信号光分别由相干光接收装置20的本振光端口和信号光端口输入；分光单元201将接收到的本振光分解得到多束子本振光，分光单元201将接收到的信号光分解得到多束子信号光，子本振光的数目与子信号光的数目相同；混频单元203将多束子信号光中的每束子信号光都与多束子本振光中的一束子本振光进行混频得到多束混频光信号；合成单元204将多束混频光信号进行光电转换输出多个相干电信号；偏振控制单元202调节本振光的偏振使DSP根据上述多个相干电信号得到业务数据。可选地，偏振控制单元202调节本振光的偏振包括调节本振光的相位。
一种可能的设计中，分光单元201分解得到的多个子信号光和多个子本振光的偏振态也是随机的，不是线偏振光。
另一种可能的设计中，分光单元201可以是偏振分光单元，那么此时：
分光单元201将接收到的本振光分解得到多束子本振光，将接收到的信号光分解得到多束子信号光，具体包括：
将信号光分解为至少一束第一子信号光和至少一束第二子信号光以及将本振光分解为至少一束第一子本振光和至少一束第二子本振光，其中，第一子信号光和第一子本振光为X偏振态，第二子本振光和第二子信号光为Y偏振态。
混频单元203将多束子信号光中的每束子信号光都与多束子本振光中的一束子本振光进行混频得到多束混频光信号，具体包括：
混频单元203将第一子信号光和第一子本振光进行混频以及将第二子信号光与第二子本 振光进行混频，得到多束混频光。即每束第一子信号光都与一束第一子本振光混频，每束第二子信号光都与一束第二子本振光混频。
可选的，合成单元204可以先将混频单元203混频后输出的多束混频光信号中的每两束光信号合成为一束得到多路合束光信号，合束光信号的数目是混频光信号数目的一半，再对多路合束光信号进行光电转换输出多个相干电信号。
本振光的偏振态随机变化，会存在一些偏振态使相干光接收装置不能工作，本申请该实施例提供的相干光接收装置通过引入偏振控制单元来调节本振光的偏振，使本振光避开这些使相干光接收装置不能工作的偏振态，从而使相干光接收装置保持正常工作。
图3为本申请实施例公开的相干光接收装置的第二实施例示意图。
如图3所示，本申请实施例中相干光接收装置30包括：信号光输入端口301、本振光输入端口302、偏振分束模块303、功率均分模块304、混频器1 305、混频器2 306、混频器3 307、混频器4 308、偏振合束模块309、第一光电转换模块310、第二光电转换模块311、耦合分束模块312、相位调制器313、第三光电转换模块314、信号处理模块315和ODSP(Optical Digital Signal Processing，光数字信号处理器)316。其中，相位调制器可以是通用的移相器(PS,Phase Shifter)，还可以是半波片、透镜等能够进行相位调制的元件。
这里，本申请所描述的偏振分束模块、功率均分模块和偏振合束模块是为了方便描述和理解，主要是将装置中功能类似的部件放在一起；本申请所描述的光电转换模块、耦合分束模块和信号处理模块是对一定范围的部件进行了功能概括，上述模块的划分为了便于方案的理解，实际中可以存在不同的模块划分。
图2实施例中的偏振分光单元201包括本实施例中的偏振分束模块303和功率均分模块304；偏振控制单元202包括耦合分束模块312、相位调制器313、第三光电转换模块314和信号处理模块315；混频单元203包括混频器1 305、混频器2 306、混频器3 307和混频器4 308；合成单元204包括偏振合束模块309、第一光电转换模块310和第二光电转换模块311。
信号光S由信号光输入端口301输入，偏振分束模块303中的PSR1(Polarization Splitter and Rotator，偏振分束旋转器)将信号光S进行偏振分束得到第一信号光S X和第二信号光S Y,即信号光的X偏振态光和Y偏振态光；之后功率均分模块304中的BS1(Beam Splitter，分束器)将第一信号光S X分束得到两束第一子信号光F1和F7，其中F1＝F7＝S X/2，BS2将第二信号光S Y分束得到两束第二子信号光F3和F4，其中F3＝F5＝S Y/2。本振(Local Oscillator，LO)光由本振光输入端口302输入，偏振分束模块303中的PSR2将信号光S进行偏振分束得到第一本振光LO X和第二本振光LO Y，即本振光的X偏振态光和Y偏振态光；之后功率均分模块304中的BS3(Beam Splitter，分束器)将第一本振光LOX分束得到两束第一子本振光F2和F6，其中F2＝F6＝LO X/2，BS4将第二本振光LO Y分束得到两束第二子本振光F4和F8，其中F4＝F8＝LO Y/2。其中，第一本振光LO X和第二本振光LO Y在进入BS3和BS4之前，会被BS5和BS6各分出去一小部分光用于偏振控制。
混频器1 305接收F1和F2进行混频得到4路混频光T1、T2、T3、T4，混频器2 306接收F3和F4进行混频得到4路混频光T5、T6、T7、T8，混频器3 307接收F5和F6进行混频得到4路混频光T9、T10、T11、T12，混频器4 308接收F7和F8进行混频得到4路混频光T13、T14、T15、T16。这里即得到16束混频光。
图4是本申请实施例公开的一种混频器的结构示意图，以混频器1 305为例，该混频器 包括分光器1 401、分光器2 402、分光器3 403、分光器4 404和90度移相器405，分光器1 401接收光束F1并对F1进行分束得到两束
Figure PCTCN2020117043-appb-000001
分光器3 403接收光束F3并对F3进行分束得到两束
Figure PCTCN2020117043-appb-000002
90度移相器405对其中一束
Figure PCTCN2020117043-appb-000003
移相90度得到
Figure PCTCN2020117043-appb-000004
如图4所示，分光器2 402接收光束
Figure PCTCN2020117043-appb-000005
和
Figure PCTCN2020117043-appb-000006
耦合分束得到(F1+F2)/2和(F1-F2)/2，分光器3 403接收
Figure PCTCN2020117043-appb-000007
和
Figure PCTCN2020117043-appb-000008
耦合分束得到混频光(F1+j*F2)/2和(F1-j*F2)/2，代入F1＝S X/2，F2＝LO X/2，可得
Figure PCTCN2020117043-appb-000009
混频器2 306、混频器3 307和混频器4 308的结构原理与混频器1 305类似，那么上述16束混频光具体可以如下：
Figure PCTCN2020117043-appb-000010
Figure PCTCN2020117043-appb-000011
Figure PCTCN2020117043-appb-000012
Figure PCTCN2020117043-appb-000013
由此可见，本申请实施例提供的方案中混频单元有4个混频器，在进行信号光与本振光进行混频如下4种情况均包括在内：信号光的X偏振态与本振光的X偏振态混频、信号光的X偏振态与本振光的Y偏振态混频、信号光的Y偏振态与本振光的X偏振态混频和信号光的Y偏振态与本振光的Y偏振态混频。现有的相干光接收装置通常只包括上述4种情况中的2种，如上图1b所示，通常是将信号光的X偏振态与本振光的Y偏振态混频以及将信号光的Y偏振态与本振光的X偏振态混频两种情况。当信号光与本振光的偏振态都是随机的时候，很可能会出现光信号的能量集中在某一偏振态上，另一偏振态上几乎没有能量。还是接着上文的举例，假设本振光的能量集中在X偏振态上，本振光的Y偏振态几乎没有能量，那么在现有的相干光接收装置下，信号光的X偏振态与本振光的Y偏振态就没法进行正常的混频，那么信号光X偏振态所携带业务数据就缺损了。在本申请实施例方案下，信号光的X偏振态与本振光的X偏振态混频依然可以正常进行混频。因此，本申请实施例有效地避免了本振光的偏振态随机变化导致接收机无法正常工作的问题。
上述16束混频光可以先经过偏振合束进行合束，再经过光电转换得到多个相干电信号。具体地，偏振合束模块309包括8个PRC(Polarization Rotator and combiner，偏振旋转合束器)，每个PRC将16束混频光中的两束混频进行合束。例如，如图3所示，PRC1将混频光T1和T5合束，PRC2将混频光T2和T6合束，PRC3将混频光T3和T7合束，PRC4将混频光T4和T8合束，PRC1将混频光T1和T5合束，以此类推，将混频器1 305中第x输出光束和混频器2 306中第(x+a)输出光束合成为一路，以及将混频器3 307中第x输出光束和混频器4 308中第(x+a)输出光束合成为一路。其中，a为PRC输出的光束数目。以PRC1为例，PRC1合束T1和T5，合束过程中一般会有损耗，这里以T1和T5都损耗一半来计算，那么合成后的光束
Figure PCTCN2020117043-appb-000014
同理可得，
Figure PCTCN2020117043-appb-000015
光束E1和E2分别经过第一光电转换模块310中的PD1(Photonic detector，光电探测器)和PD2接收得到电域信号：
Figure PCTCN2020117043-appb-000016
Figure PCTCN2020117043-appb-000017
经过第一光电转换模块310加减器1加减后:Q1-Q2，加减器1输出的相干电信号I 1,I为
Figure PCTCN2020117043-appb-000018
同理可得，加减器2输出的相干电信号I 1,Q为：
Figure PCTCN2020117043-appb-000019
加减器3输出的相干电信号I 2,I为：
Figure PCTCN2020117043-appb-000020
加减器4输出的相干电信号I 2,Q为：
Figure PCTCN2020117043-appb-000021
运算real表示取实部，运算imag表示取虚部。
I 1,I、I 1,Q、I 2,I、I 2,Q四路相干电信号经过各自的跨阻放大器(trans-impedance amplifier，TIA)放大后再被模数转换器(analog digital converter，ADC)采样后送入ODSP316中处理恢复业务数据。可选地，相干光接收装置30可以包括ODSP316,ODSP316也可以位于相干光接收装置30外。
ODSP316在根据相干电信号恢复获得业务数据，可能存在本振光的偏振旋转角或偏振延时角在特定取值的时候，ODSP316无法根据相干电信号恢复获得业务数据。
具体地，在ODSP316中，两路复数信号I 1、I 2，可被推导得到如下关系：
Figure PCTCN2020117043-appb-000022
若矩阵
Figure PCTCN2020117043-appb-000023
健康可逆，则ODSP316中的MIMO算法即可从两路复数信号中
Figure PCTCN2020117043-appb-000024
恢复得到业务数据。
本征光在发端为线偏振光，可以写为
Figure PCTCN2020117043-appb-000025
经过光纤信道传输后(经历琼斯矩阵)到达接收端的本征光可表示为
Figure PCTCN2020117043-appb-000026
其中θ为本振光的偏振旋转角，
Figure PCTCN2020117043-appb-000027
为本振光的偏振延时角。将该式带入M矩阵可得:
Figure PCTCN2020117043-appb-000028
由上式(1)可发现当cosθ＝sinθ，
Figure PCTCN2020117043-appb-000029
该M矩阵就不可逆，ODSP316无法根据相干电信号恢复获得业务数据。
本申请实施例通过引入偏振控制单元调节本振光的偏振使ODSP316根据所述多个相干电信号得到业务数据。具体地，通过对本振光经过PSR2后的第一本振光LOX和第二本振光LOY中的其中一路上添加相位调制器313。在图3中，相位调制器313放在第二本振光LOY支路上，可选地，相位调制器313也可以放在第一本振光LOX支路上。通过对相位调制器的控制来调节第一本振光或第二本振光的偏振延时角
Figure PCTCN2020117043-appb-000030
可以达到控制矩阵M始终健康可逆的状态。
设相位调制器313对第一本振光或第二本振光的偏振延时角
Figure PCTCN2020117043-appb-000031
引入相位
Figure PCTCN2020117043-appb-000032
的变化，则矩阵M可以改写为：
Figure PCTCN2020117043-appb-000033
图5是本振光对应的邦加球示意图。如图5所示，本振光的偏振旋转角θ和本振光的偏振延时角
Figure PCTCN2020117043-appb-000034
在遍历取值后，本振光的偏振态都落在邦加球的球面上。经过相位调制器313对第一本振光或第二本振光的偏振延时角
Figure PCTCN2020117043-appb-000035
引入相位
Figure PCTCN2020117043-appb-000036
调节后的本振光落在球面上黑色的区间内，M矩阵就达到健康可逆的状态。因此，偏振控制单元202只需要将在球面随机扰动的本振光绕开白色的区间，落在黑色区间上，就可以使ODSP316根据相干电信号恢复获得业务数据，相干光接收装置正常工作，大大降低了反馈控制的难度。在现有的相干光接收装置下，往往需要将在球面随机扰动的本振光调控在其中一点或一小块区域，调控难度高。本申请实施例提供的偏振控制降低了偏振控制的难度和精度，节约了设计成本。
图6是本申请实施例提供的偏振控制方法流程图，具体地，偏振控制单元202控制过程如下：
步骤601：分出一部分本振光，并将这部分本振光分束得到多束光监控信号；
耦合分束模块312包括多个BS，其中，BS5和BS6各自耦合出一小部分本振光，这两束光分别再分别被BS7和BS8均分为4路光监控信号,其中两路再经过BS9耦合相加得到如下3路混频光：
Figure PCTCN2020117043-appb-000037
步骤602：将多束光监控信号转换为多束电监控信号；
上述3路混频光再经过第三光电转换模块314中PD9、PD10、PD11接收,TIA5、TIA6、TIA7放大，ADC5、ADC6、ADC7采样得到3路电监控信号：
Figure PCTCN2020117043-appb-000038
步骤603：根据多束电监控信号生成反馈控制电信号，该反馈控制电信号用于控制相位调制器以调节本振光的偏振使ODSP316根据上述多个相干电信号得到业务数据。
具体地，信号处理模块315监控电监控信号的能量：
当I10和I30的差值在预设的一定范围内，表明偏振旋转角θ在0度或90度附近，矩阵M很健康，相位调制器313不用工作；
当I 10和I 30的能量接近时，需要启动相位调制器313控制本振光的偏振，则此时信号处理模块315生成反馈控制信号调节相位调制器313，当相位调制器313通过调节使得(I 2-I 1-I 3)的能量变大，可以判定目前的M矩阵可逆，相干光接收装置可以正常工作。可选地，反馈控制电信号控制相位调制器313以调节上述第一本振光或第二本振光的相位使ODSP316根据上述多个相干电信号得到业务数据。进一步地，调节上述第一本振光或第二本振光的相位包括调节上述第一本振光或第二本振光的偏振延时角。例如，相位调制器313对第一本振光或第二本振光相位调制器313引入的相位
Figure PCTCN2020117043-appb-000039
当
Figure PCTCN2020117043-appb-000040
趋近于90度时，即第一本振光或第二本振光的偏振延时角
Figure PCTCN2020117043-appb-000041
加上相位调制器313引入的相位
Figure PCTCN2020117043-appb-000042
后趋近于90度，则认为此时相干光接收装置可以正常工作。
具体地，信号处理模块315包括DSP3151、DAC3152(digital-to-analog converter，数模转换器)和功率放大器3153。DSP3151用于根据电监控信号生成反馈控制电信号，所述反馈控制电信号用于控制相位调制器以调节本振光的偏振使上述ODSP316根据多个相干电信号得到业务数据。DAC3152用于对反馈控制电信号进行数模转换。功率放大器3153用于对经过数模转换的反馈控制电信号进行功率放大。
可选的，BS5和BS6可以选取90:10或者95:5的分光器，即耦合出各自支路上10％的本振光或5％的本振光用于偏振控制。
综上，本申请实施例公开的相干光接收装置解决了本振光的偏振态随机变化导致接收机无法正常工作的难题，通过引入偏振控制使相干光接收装置可以保持正常恢复业务数据，进一步提升了相干光接收的稳定性，同时对偏振控制单元进行简化，降低了偏振控制的难度和精度，节约成本。
本申请提及的移相90度或偏振态旋转90度也有可能移相270度或偏振态旋转270度，应理解，与移相90度或偏振态旋转90度相同技术效果的移相或偏转态度数均可。需要说明的是，前述提到的旋转的度数因实际器件工艺限制等原因可能有较小的偏差。应理解，本申请提及的移相90度或偏振态旋转90度包括这种近似90度或者270度的旋转。
需要说明的是，本申请实施例提及的PSR可以替换为PBS(Polarization Beam Splitter，偏振分束器)和PR(Polarization Rotator，偏振旋转器)连接的组合，PRC可以替换为PBC(Polarization Beam Combiner，偏振合束器)和PR连接的组合。应理解，将PSR替换为PBS和PR连接的组合以及将PRC替换为PBC和PR的组合属于结构简单变形，也属于本申请保护的技术方案。分光器可以为波导耦合器或者多模干涉(Multimode interferometer,MMI)耦合器。
为了方便描述和理解，本申请各个实施例相同的模块或部件采用相同的附图编号。
图7为本申请实施例公开的相干光接收装置的第三实施例示意图。
如图7所示，该相干光接收装置70包括：信号光输入端口301、本振光输入端口302、偏振分束模块303、功率均分模块304、混频器1 305、混频器2 306、混频器3 307、混频器4 308、光电转换模块701、耦合分束模块312、相位调制器313、第三光电转换模块314、信号处理模块315和ODSP316。其中，为了简化附图表示，信号光输入端口301、本振光输入端口302、偏振分束模块303、功率均分模块304、耦合分束模块312、相位调制器313、第三光电转换模块314和信号处理模块315与图3表示的相同，在图7中未示出。图7与图3不同的地方主要在于对混频单元输出的16束混频光进行处理的光电转换模块701，混频器1 305、混频器2 306、混频器3 307、混频器4 308之前的结构参考图3即可。
混频器1 305、混频器2 306、混频器3 307、混频器4 308输出的16束混频光T1～T16，分别先由PD1～PD16转换为电信号，再经过加减器加减后得到多个相干电信号。
例如T1、T2和T5、T6经过PD检测后得到4路混频电信号：
Figure PCTCN2020117043-appb-000043
上述Q1、Q2经过加减器1加减后得到：
Figure PCTCN2020117043-appb-000044
Q5、Q6经过加减器5加减后得到：
Figure PCTCN2020117043-appb-000045
上述Q1-Q2和Q5-Q6的两路电信号再经过加减器2得到相干电信号I 1,I,
Figure PCTCN2020117043-appb-000046
同理可得，加减器4输出的相干电信号I 1,Q为：
Figure PCTCN2020117043-appb-000047
加减器8输出的相干电信号I 2,I为：
Figure PCTCN2020117043-appb-000048
加减器10输出的相干电信号I 2,Q为：
Figure PCTCN2020117043-appb-000049
为了使得电域上相加的信号方便布线，如图7所示，可以调换混频器2 306和混频器4 308输出混频光的顺序，以减少混频器之后的光路交叉。
本申请该实施例提供的相干光接收装置没有对混频器输出的混频光采用光路偏振合束方案，而是直接通过增加加减器进行加减，避免偏振合束所带来的耦合损耗，插损更小。
图8为本申请实施例公开的相干光接收装置的第四实施例示意图。
如图8所示，该相干光接收装置80包括BS1 801、BS2 802、偏振分束模块803、PSR4 804、PSR6 805和偏振控制模块806；另外还包括信号光输入端口301、本振光输入端口302、混频器1 305、混频器2 306、混频器3 307、混频器4 308、相位调制器313、ODSP316，参见图3相关描述即可。偏振分束模块803包括4个PSR：PSR1、PSR2、PSR3和PSR4。图8与图3所示的实施例主要区别在于，对信号光和本振光的偏振分束进行了光路的简化。
信号光S由信号光输入端口301输入，经过BS1 801功率分束后第一信号光和第二信号光，偏振分束模块803中的PSR1将第一信号光进行偏振分束得到一束第一子信号光F1和一束第二子信号光F7，PSR3将第二信号光进行偏振分束得到另一束第一子信号光F3和一束第二子信号光F5，其中，第一子信号光为X偏振态，第二子信号光为Y偏振态。
本振光LO由本振光输入端口302输入，先经过PSR5 804偏振分束得到第三本振光和第四本振光，第三本振光为X偏振态，第四本振光为Y偏振态，BS5和BS6分别耦合出一部分本振光输入到偏振控制模块806用于偏振控制，根据上述一部分本振光得到光监控信号，光监控信号转换为电监控信号，根据电监控信号生成反馈控制信号控制相位调制器313调节第四本振光的相位。偏振控制模块806具体原理可以参见图3相关描述。PRC6 805将经过BS5和BS6的第三本振光和第四本振光偏振合束并输入到BS2 802。
偏振控制模块806可以包括图3实施例中的耦合分束模块312中的BS7、BS8、BS9以及第三光电转换模块314、信号处理模块315和ODSP316。
BS2 802将本振光功率分束得到第一本振光和第二本振光，偏振分束模块803中的PSR2将第一本振光进行偏振分束得到一束第一子本振光F2和一束第二子本振光F6，PSR4将第二本振光进行偏振分束得到另一束第一子本振光F4和一束第二子本振光F8，其中，第一子本振光为X偏振态，第二子本振光为Y偏振态。
图8混频器之后还可以连接图7种的光电转换模块701；也可以连接图3中的偏振合束模块309，之后再连接第一光电转换模块310和第二光电转换模块311。
本申请图3的偏振分光方案是先经过PSR偏振分束在进行BS功率分束，而本申请图8的偏振分光方案是先进行BS功率分束再进行PSR偏振分束。在实际光路中，对信号光和本振光的偏振分光，也可以信号光采用图3实施例中偏振分光方案，本振光采用图8实施例中的偏振分光方案；或者，也可以信号光采用图8实施例中偏振分光方案，本振光采用图3实施例中的偏振分光方案。本申请实施例仅展示可能的组合方案，建议在本申请实施例基础上，将本申请实施例的结构进行容易想到的组合应当也包含在本申请的保护范围内。
图9为本申请实施例公开的相干光接收装置的第五实施例示意图。
如图9所示，该相干光接收装置90包括：光纤准直器901、光纤准直器902、透镜1 903、透镜1 904、反射组件1 905、反射组件2 906、旋偏器907、混频器908和混频器909；另外还包括信号光输入端口301、本振光输入端口302、相位调制器313和偏振控制模块806，参见图3和图8相关描述即可。
信号光经由光纤准直器901准直后，输入到透镜1 903，透镜1 903将信号光分解为第一信号光和第二信号光；本振光经由光纤准直器902准直后，输入到透镜2 904，透镜2 904将本振光分解为第一本振光和第二本振光，第二本振光经过旋偏器907旋偏后进入混频器909。混频器908将第一信号光和第一本振光进行混频，混频器909将第二信号光和第二本振光进行混频。混频器908和混频器909可以为空间混频器。
可选地，反射组件1 905可以对第二信号光进行反射以使第二信号光输入到混频器908，反射组件2 906可以对第二本振光进行反射以使第二本振光输入到混频器907。
可选地，旋偏器可以为90度偏振旋偏器。
图10为本申请实施例公开的一种光***的示意图。
如图10所示，该光***100包括：光发送设备1001、光纤1002和相干光接收装置1003。 相干光接收设备1003通过光纤1002接收光发送设备1001发送的信号光；相干光接收设备1003通过光纤1002接收本振光或者相干光接收设备1003产生本振光。相干光接收设备1003可以是上述实施例中任意一种相干光接收装置。
本申请中的各个实施例之间相同相似的部分互相参见即可，尤其，对于图7～图10实施例而言，是对图3～图6对应的实施例的扩展，所以描述的比较简单，相关之处参见图3～图6对应实施例的部分说明即可。
最后应说明的是：以上所述仅为本申请的具体实施方式，本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。

Claims (16)

  1. 一种相干光接收装置，其特征在于，包括：
    分光单元、偏振控制单元、混频单元和合成单元，所述偏振分光单元与所述混频单元的输入端连接，所述混频单元的输出端与所述合成单元连接；
    所述分光单元，用于接收任意偏振模式的信号光和本振光，并将所述信号光分解为多束子信号光，将所述本振光分解为多束子本振光；
    所述混频单元，用于将所述子信号光和所述子本振光进行混频，得到多束混频光；
    所述合成单元，用于将所述多束混频光进行光电转换得到输出多个相干电信号；
    所述偏振控制单元，用于控制所述本振光的偏振使第一数字信号处理器(DSP)根据所述多个相干电信号得到业务数据。
  2. 如权利要求1所述的相干光接收装置，其特征在于，包括：
    所述分光单元接收任意偏振模式的信号光和本振光，并将所述信号光分解为多束子信号光，将所述本振光分解为多束子本振光，具体包括：
    所述分光单元接收所述任意偏振模式的信号光，并将所述信号光分解为至少一束第一子信号光和至少一束第二子信号光，所述第一子信号光为第一偏振模式，所述第二子信号光为第二偏振模式；所述分光单元接收所述任意偏振模式的本振光，并将所述本振光分解为至少一束第一子本振光和至少一束第二子本振光，所述第一子本振光为所述第一偏振模式，所述第二子本振光为所述第二偏振模式；
    所述混频单元将所述子信号光和所述子本振光进行混频得到多束混频光，具体包括：
    所述混频单元将所述第一子信号光和所述第一子本振光进行混频以及将所述第二子信号光与所述第二子本振光进行混频得到所述多束混频光。
  3. 如权利要求2所述的相干光接收装置，其特征在于，所述偏振控制单元包括多个第一分束器(BS)、相位调制器、第一光电转换模块和信号处理模块；
    所述多个第一BS用于耦合出一部分本振光并分束得到多束光监控信号；
    所述第一光电转换模块用于将所述光监控信号转换成电监控信号；
    所述信号处理模块用于根据所述电监控信号生成反馈控制电信号，所述反馈控制电信号用于控制所述相位调制器以调节所述本振光的偏振使第一DSP根据所述多个相干电信号得到所述业务数据。
  4. 如权利要求2或3所述的相干光接收装置，其特征在于，所述偏振分光单元包括第一偏振分束旋转器(PSR)、第二PSR、第二BS、第三BS、第四BS和第五BS；
    所述偏振分光单元用于将所述信号光分解为至少一束第一子信号光和至少一束第二子信号光，所述第一子信号光为所述第一偏振模式，所述第二子信号光为所述第二偏振模式，包括：
    所述第一PSR用于将所述信号光分解为第一信号光和第二信号光，所述第一信号光为所述第一偏振模式，所述第二信号光为所述第二偏振模式；
    所述第二BS用于将所述第一信号光均分为两束所述第一子信号光；
    所述第三BS用于将所述第二信号光均分为两束所述第二子信号光；
    所述偏振分光单元用于将所述本振光分解为至少一束第一子本振光和至少一束第二子本振光，所述第一子本振光为所述第一偏振模式，所述第二子本振光为所述第二偏振模式，包括：
    所述第二PSR用于将所述信号光分解为第一本振光和第二本振光，所述第一本振光为所述第一偏振模式，所述第二本振光为所述第二偏振模式；
    所述第四BS用于将所述第一本振光均分为两束所述第一子本振光；
    所述第五BS用于将所述第二本振光均分为两束所述第二子本振光。
  5. 如权利要求4所述的相干光接收装置，其特征在于，所述偏振控制单元调节所述本振光的偏振使第一DSP根据所述多个相干电信号得到业务数据，包括：
    所述偏振控制单元调节所述第一本振光和/或第二本振光的偏振延迟角使所述第一DSP根据所述多个相干电信号得到所述业务数据。
  6. 如权利要求2所述的相干光接收装置，其特征在于，所述偏振分光单元包括第一BS、第二BS、第一PSR、第二PSR、第三PSR和第四PSR；
    所述偏振分光单元用于将所述信号光分解为至少一束第一子信号光和至少一束第二子信号光，所述第一子信号光为所述第一偏振模式，所述第二子信号光为所述第二偏振模式，包括：
    所述第一BS用于将所述信号光均分为第一信号光和第二信号光；
    所述第一PSR用于将所述第一信号光分解为一束所述第一子信号光和一束所述第二子信号光；
    所述第二PSR用于将所述第二信号光分解为另一束所述第一子信号光和另一束所述第二子信号光；
    所述偏振分光单元用于将所述本振光分解为至少一束第一子本振光和至少一束第二子本振光，所述第一子本振光为所述第一偏振模式，所述第二子本振光为所述第二偏振模式，包括：
    所述第二BS用于将所述本振光为第一本振光和第二本振光；
    所述第三PSR用于将所述第一信号光分解为一束所述第一子本振光和一束所述第二子本振光；
    所述第四PSR用于将所述第二信号光分解为另一束所述第一子本振光和另一束所述第二子本振光。
  7. 如权利要求2至6任一所述的相干光接收装置，其特征在于，所述混频单元包括至少一个混频器，所述混频器包括第一分光器、第二分光器、第三分光器、第四分光器和90度移相器，
    所述第一分光器用于将一束所述第一子信号光均分为两束第一分束子信号光，所述第三分光器用于将一束所述第一子本振光均分为两束第一分束子本振光；
    所述90度移相器用于将其中一束所述第一分束子本振光移相90度；
    所述第二分光器用于将一束所述第一分束子信号光和一束所述第一分束子本振光合成后输出两束混频光；
    所述第四分光器用于将另一束所述第一分束子信号光和所述经过移相90度的第一分束子本振光合成后输出另两束混频光。
  8. 如权利要求1所述的相干光接收装置，其特征在于，所述分光单元包括第一光纤准直器、第二光纤准直器、第一透镜、第二透镜、反射组件和旋偏器；
    所述分光单元接收任意偏振模式的信号光和本振光，并将所述信号光分解为多束子信号光，将所述本振光分解为多束子本振光，包括：
    所述第一光纤准直器用于接收所述信号光并准直；
    所述第二光纤准直器用于接收所述本振光并准直；
    所述第一透镜用于将所述信号光分成第一子信号光和第二子信号光；
    所述第二透镜用于将所述本振光分成第一子本振光和第二子本振光，所述旋偏器用于将所述第二子本振光偏振旋转；
    所述反射组件包括多个反射镜，所述反射组件用于将所述第一子信号光、所述第二子信号光、所述第一子本振光或所述第二子本振光反射到所述混频单元。
  9. 如权利要求8任一所述的相干光接收装置，所述混频单元包括第一混频器和第二混频器；
    所述第一混频器用于将所述第一子信号光和所述第一子本振光进行混频，以及所述第二混频器将所述第二子信号光和所述经过偏振旋转的第二子本振光进行混频；
    所述第一混频器和所述第二混频器，还用于输出所述多束混频光。
  10. 如权利要求6至9任一所述的相干光接收装置，其特征在于，所述偏振控制单元包括多个第三BS、相位调制器、光电转换模块和信号处理模块；
    所述多个第三BS用于耦合出一部分本振光并分束得到多束光监控信号；
    所述光电转换模块用于将所述光监控信号转换成电监控信号；
    所述信号处理模块用于根据所述电监控信号生成反馈控制电信号，所述反馈控制电信号用于控制所述相位调制器以调节所述本振光的偏振使所述第一DSP根据所述多个相干电信号得到所述业务数据。
  11. 如权利要求10所述的相干光接收装置，其特征在于，所述偏振控制单元还包括第三PSR和第一偏振旋转合束器(PRC)，所述PRC的输出端连接所述第二BS输入端；
    所述第三PSR用于接收所述本振光并将所述本振光分解为第三本振光和第四本振光，所述第三本振光为所述第一偏振模式，所述第四本振光为所述第二偏振模式；
    所述多个第三BS耦合出一部分本振光并分束得到多束光监控信号，包括：
    所述多个第三BS分别从所述第三本振光和所述第四本振光分出所述一部分本振光并分束得到所述多束光监控信号；
    所述反馈控制电信号控制所述相位调制器以调节所述本振光的偏振使第一数字信号处理器(DSP)根据所述多个相干电信号得到业务数据，包括：
    所述反馈控制电信号控制所述相位调制器以调节所述第三本振光或第四本振光的相位使所述第一DSP根据所述多个相干电信号得到所述业务数据；
    所述第一PRC用于将经过所述第三BS后的第三本振光和第四本振光进行偏振合束。
  12. 如权利要求1至11任一所述的相干光接收装置，其特征在于，所述合成单元包括多个第二PRC、多个第二光电转换模块；
    所述第二PRC用于将所述多束混频光中的其中两束混频光合束；
    所述多个第二光电转换模块用于将多个所述经过第二PSR合束后的混频光转换成所述多个相干电信号。
  13. 如权利要求1至11任一所述的相干光接收装置，其特征在于，所述合成单元包括第三光电转换模块，所述第三光电转换模块包括多个光电探测器(PD)、多个电域加减器、多个跨阻放大器(TIA)和多个模数转换器ADC；
    所述PD用于将所述多束混频光转换成多束混频电信号；
    所述多个电域加减器用于将多束混频电信号合成得到所述多个相干电信号；
    所述TIA用于将所述多个相干电信号放大；
    所述ADC用于对所述多个相干电信号进行模数转换。
  14. 如权利要求3至5或10至11中任一所述的相干光接收装置，其特征在于，所述信号处理模块包括第二DSP、数模转换器(DAC)和功率放大器；
    所述第二DSP用于根据所述电监控信号生成所述反馈控制电信号；
    所述DAC用于对所述反馈控制电信号进行数模转换；
    所述功率放大器用于对所述经过数模转换的反馈控制电信号进行功率放大。
  15. 如权利要求1至14所述的相干光接收装置，其特征在于，所述相干光接收装置还包括所述第一DSP，所述第一DSP用于根据所述多个相干电信号得到所述业务数据。
  16. 一种光***，所述***包括光发送设备、光纤和如权利要求1-15任一所述的相干光接收设备，所述相干光接收设备通过所述光纤接收所述光发送设备发送的所述信号光；所述相干光接收设备接收所述本振光或者所述相干光接收设备产生所述本振光，具体包括：
    所述相干光接收设备通过所述光纤接收所述光发送设备发送的所述本振光；或者，所述相干光接收设备产生所述本振光。
PCT/CN2020/117043 2019-12-31 2020-09-23 相干光接收装置和采用相干光接收装置的光*** WO2021135428A1 (zh)

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