CN112054851A

CN112054851A - Coherent light receiving device, coherent light processing method and system

Info

Publication number: CN112054851A
Application number: CN201910486707.0A
Authority: CN
Inventors: 赵平; 李良川
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2019-06-05
Filing date: 2019-06-05
Publication date: 2020-12-08
Anticipated expiration: 2039-06-05
Also published as: CN112054851B

Abstract

Coherent optical receiving devices, methods, and systems are disclosed. The coherent light receiving device performs the following steps. Firstly, polarizing and splitting an input signal light to obtain two beams of signal light; and the polarization state of one of the two signal lights is rotated to obtain the other signal light. Then, the input local oscillation light is polarized and split to obtain two beams of local oscillation light; and the polarization state of one of the two local oscillation lights is rotated to obtain the other local oscillation light. And then, carrying out phase control and coupling processing on the local oscillator light which is not subjected to polarization state rotation and the other local oscillator light to obtain two more beams of local oscillator light. And controlling the phase of the local oscillator light so that the power difference of the two local oscillator lights is smaller than a preset value. And finally, mixing and performing photoelectric conversion on the signal light which is not subjected to polarization state rotation, the other signal light and the two beams of local oscillator light to output a plurality of coherent electric signals. According to the scheme disclosed by the application, the phase of the local oscillator light is controlled, the influence of the polarization state rotation of the local oscillator light on coherent reception is eliminated, and the coherent light receiving performance is effectively improved.

Description

Coherent light receiving device, coherent light processing method and system

Technical Field

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

Background

With the rise of novel applications such as the internet of things, the network data traffic is exponentially increased. This greatly increases the application requirements of high-speed transmission techniques. For example, within data centers, the need for short haul, ultra-large bandwidth optical transmission is particularly acute. The coherent light transmission technology has the advantages of large transmission capacity, long transmission distance and the like; and is thus considered one of the important alternatives.

The current coherent optical transmission system must adopt a polarization maintaining optical fiber with a high price to connect the local oscillator laser and the coherent receiver so as to ensure that the local oscillator light has enough energy in a certain fixed polarization state, thereby ensuring the normal work of the receiver. However, in practical applications, the polarization maintaining fiber is likely to be affected by extrusion or other application environment changes, such as: treading, construction stretching, and the like. This may result in deterioration of the function of polarization state retention thereof. Then the polarization state of the local oscillator light entering the coherent receiver will randomly rotate, which will cause the coherent receiver to fail.

Disclosure of Invention

The embodiment of the application provides a coherent light receiving device and a coherent light processing method, which are used for solving the problem that a coherent light receiver cannot be normal due to polarization state rotation in the prior art.

In a first aspect, an embodiment of the present application provides a coherent light receiving apparatus. The device includes: a first Polarization Beam Splitter (PBS), a second PBS, a first Polarization Rotator (PR), a second PR, a first Phase Shifter (PS), a second PS, a coupler, and a coherent photoelectric processor. The first PBS is configured to perform polarization beam splitting on the signal light input to the coherent light receiving device, and output first signal light and second signal light with orthogonal polarization states. The first PR is configured to perform polarization rotation on the first signal light and output third signal light, where a polarization of the third signal light is the same as a polarization of the second signal light. And the second PBS is used for performing polarization beam splitting on the local oscillation light input into the coherent light receiving device and outputting first local oscillation light and second local oscillation light with orthogonal polarization states. And the first PS is used for performing phase control on the first local oscillator light and outputting third local oscillator light, and the polarization state of the third local oscillator light is the same as that of the second signal light. The second PS and the second PR are respectively configured to perform phase control and polarization rotation on the second local oscillation light, and output fourth local oscillation light, where a polarization state of the fourth local oscillation light is the same as a polarization state of the third local oscillation light. And the coupler is used for splitting and combining the third local oscillation light and the fourth local oscillation light and outputting fifth local oscillation light and sixth local oscillation light. The first PS and the second PS perform phase control on the first local oscillation light and the second local oscillation light so that a power difference between the fifth local oscillation light and the sixth local oscillation light is smaller than a preset value. And the coherent photoelectric processor is configured to receive the second signal light, the third signal light, the fifth local oscillator light and the sixth local oscillator light, perform frequency mixing and photoelectric conversion, and output a plurality of coherent electrical signals.

By carrying out phase control on the two beams of local oscillator light, the coherent light receiving device can not be influenced by random polarization state change of the local oscillator light, and the normal work of a coherent light receiver is ensured.

With reference to the first aspect, in a first specific implementation manner, the second PS and the second PR are respectively configured to perform phase control and polarization rotation on the second local oscillator light, and output fourth local oscillator light, and the method specifically includes: the second PS is configured to perform phase control on the second local oscillation light and output a seventh local oscillation light, and the second PR is configured to perform polarization rotation on the seventh local oscillation light and output a fourth local oscillation light; or the second PR is configured to perform polarization rotation on the second local oscillation light and output eighth local oscillation light, and the second PS is configured to perform phase control on the eighth local oscillation light and output the fourth local oscillation light.

With reference to the first aspect or the first specific implementation manner of the first aspect, in a second specific implementation manner, the coherent optical receiving device further includes a first Optical Splitter (OS), a second OS, a third OS, and a fourth OS, where the first to fourth OSs are respectively configured to split ninth to twelfth local oscillator lights from the third local oscillator light to the sixth local oscillator light, and the ninth to twelfth local oscillator lights are configured to determine phase adjustment amplitudes of the first PS and the second PS. The phase adjustment is carried out by adopting a light splitting mode, and the accuracy is higher. Alternatively, the splitting ratios of the four OSs are the same, and the phase adjustment amplitude calculation is simpler.

With reference to the first aspect or the first specific implementation manner of the first aspect, in a third specific implementation manner, the coherent light receiving device further includes a fifth OS and a sixth OS, where the fifth OS and the sixth OS are respectively configured to separate a thirteenth local oscillator light and a fourteenth local oscillator light from the fifth local oscillator light to the sixth local oscillator light, and the thirteenth local oscillator light and the fourteenth local oscillator light are used to determine phase adjustment amplitudes of the first PS and the second PS. And only two OS feedback control phases are adopted, so that the structure is simpler. Alternatively, the splitting ratios of the two OSs are the same, and the phase adjustment amplitude calculation is simpler.

With reference to the first aspect or any one of the first to third specific implementation manners of the first aspect, in a fourth specific implementation manner, all components of the coherent light receiving device are integrated optical components. This type of device is compact and has stable performance.

With reference to the first aspect or any one of the first to the third specific implementation manners of the first aspect, in a fifth specific implementation manner, all components of the coherent light receiving device are spatial optical components, and the coherent light receiving device further includes a first reflecting mirror and a second reflecting mirror, where: the first reflector is used for reflecting the first signal light, so that the first PR rotates the polarization state of the reflected first signal light; the second reflector is configured to reflect the second local oscillation light, so that the second PS and the second PR perform phase control and polarization rotation on the reflected second local oscillation light. This type of device is less expensive.

With reference to the first aspect or the first specific implementation manner of the first aspect, in a sixth specific implementation manner, the coherent optical receiving device further includes a Digital Signal Processor (DSP), and the DSP is configured to perform phase adjustment on the first PS and the second PS.

With reference to the second or third specific implementation manner of the first aspect, in a seventh specific implementation manner, the coherent light receiving device further includes another DSP, where the another DSP is configured to receive the ninth to twelfth local oscillator lights, determine phase adjustment amplitudes of the first PS and the second PS according to the ninth to twelfth local oscillator lights, and perform phase adjustment on the first PS and the second PS by using the phase adjustment amplitudes.

With reference to the sixth specific implementation manner of the first aspect, there are multiple specific phase adjustment manners. In a possible implementation manner, the DSP determines, according to the multiple paths of coherent electrical signals, phase adjustment amplitudes of the first PS and the second PS, so that a power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value. In another possible mode, the DSP determines the phase adjustment amplitudes of the first PS and the second PS according to a part of the electrical signals of the multi-path coherent electrical signal, so that a power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value.

It should be noted that, in the above-mentioned multiple specific phase adjustments, the DSP may perform the phase adjustment only on one of the first PS and the second PS, so that a power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value. This adjustment is simple. Optionally, the DSP is further configured to process the multiple coherent electrical signals to obtain traffic data.

In a second aspect, embodiments of the present application provide a coherent optical receiving device. The apparatus comprises a coherent light receiving device as described in the first aspect or any one of the implementation manners of the first aspect. Receiving the local oscillator light by the coherent light receiving equipment; or, the coherent light receiving device generates the local oscillation light.

In a second aspect, an embodiment of the present application provides an optical system. The optical system comprises an optical transmitting device, an optical fiber and a coherent optical receiving device as described in the second aspect. The coherent light receiving device receives the signal light transmitted by the light transmitting device through the optical fiber; the receiving, by the coherent light receiving device, the local oscillator light or the local oscillator light generated by the coherent light receiving device specifically includes: the coherent light receiving device receives the local oscillator light sent by the sending device through the optical fiber; or, the coherent light receiving device generates the local oscillation light.

In a third aspect, embodiments of the present application provide another coherent light receiving apparatus. The coherent light receiving device comprises a first PBS, a second PBS, a first PR, a second PR, a first PS, a second PS, a coupler and a coherent photoelectric processor. The first PBS is configured to perform polarization beam splitting on the signal light input to the coherent light receiving device, and output first signal light and second signal light with orthogonal polarization states. And the second PBS is used for performing polarization beam splitting on the local oscillation light input into the coherent light receiving device and outputting first local oscillation light and second local oscillation light with orthogonal polarization states. And the first PS is used for carrying out phase control on the first local oscillation light and outputting third local oscillation light. The second PS and the first PR are respectively configured to perform phase control and polarization rotation on the second local oscillation light, and output fourth local oscillation light. And the coupler is used for splitting and combining the third local oscillation light and the fourth local oscillation light and outputting fifth local oscillation light and sixth local oscillation light. And the second PR is used for performing polarization state rotation on the fifth polarized light and outputting seventh local oscillation light. The first PS and the second PS perform phase control on the first local oscillation light and the second local oscillation light, so that a power difference between the seventh local oscillation light and the sixth local oscillation light is smaller than a preset value. The coherent photoelectric processor is configured to receive the first signal light, the second signal light, the sixth local oscillator light, and the seventh local oscillator light, perform frequency mixing and photoelectric conversion, and output a plurality of coherent electrical signals.

In a possible specific implementation manner, the coherent optical receiving device further includes four OSs, where the four OSs are respectively configured to separate eighth to eleventh local oscillator light from the third local oscillator light, the fourth local oscillator light, the sixth local oscillator light, and the seventh local oscillator light, and the eighth to eleventh local oscillator light are configured to determine phase adjustment amplitudes of the first PS and the second PS. The phase adjustment is carried out by adopting a light splitting mode, and the accuracy is higher. Alternatively, the splitting ratios of the four OSs are the same, and the phase adjustment amplitude calculation is simpler.

It should be noted that other specific implementations and related advantages of the first aspect are also applicable to the third aspect, and are not described herein again.

In a fourth aspect, an embodiment of the present application provides a coherent light processing method. The method comprises the following steps. Polarization beam splitting is performed on signal light input into the coherent light receiving device to obtain first signal light and second signal light with orthogonal polarization states, and polarization rotation is performed on the first signal light to obtain third signal light. And carrying out power beam splitting on the local oscillation light input into the coherent light receiving device to obtain a first local oscillation light and a second local oscillation light which are orthogonal in polarization state. And carrying out polarization rotation on the first local oscillation light to obtain third local oscillation light. And after performing phase control on the third local oscillator light and the fourth local oscillator light, performing coupling processing on the third local oscillator light and the fourth local oscillator light to obtain fifth local oscillator light and sixth local oscillator light, wherein the phase control is performed on the third local oscillator light and the fourth local oscillator light so that the power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value. And after the first signal light, the third signal light, the fifth local oscillator light and the sixth local oscillator light are subjected to frequency mixing and photoelectric conversion, outputting a plurality of paths of coherent electric signals.

In a fifth aspect, embodiments of the present application provide another coherent light processing method. The method comprises the following steps. The method comprises the steps of carrying out polarization beam splitting on signal light input into a coherent light receiving device to obtain first signal light and second signal light of orthogonal polarization states, and carrying out power beam splitting on local oscillator light input into the coherent light receiving device to obtain first local oscillator light and second local oscillator light of orthogonal polarization states. And carrying out polarization rotation on the first local oscillation light to obtain third local oscillation light. And after performing phase control on the third local oscillator light and the fourth local oscillator light, performing coupling processing on the third local oscillator light and the fourth local oscillator light to obtain fifth local oscillator light and sixth local oscillator light, wherein the phase control is performed on the third local oscillator light and the fourth local oscillator light so that the power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value. And carrying out polarization state rotation on the fifth local oscillation light to obtain seventh local oscillation light. And after the first signal light, the second signal light, the fifth local oscillation light and the seventh local oscillation light are subjected to frequency mixing and photoelectric conversion, outputting a plurality of paths of coherent electric signals.

Compared with the prior art, the coherent light receiving scheme disclosed by the application has the advantages that the two beams of local oscillator light are subjected to phase control, so that the local oscillator light power entering the frequency mixer is basically the same, the influence of random change of the local oscillator light on a coherent receiver is eliminated, and the performance of the coherent receiver is improved.

Drawings

Embodiments of the present application will now be described in more detail with reference to the accompanying drawings, in which:

fig. 1a is a schematic diagram of a possible application scenario according to an embodiment of the present application;

FIG. 1b is a schematic diagram of another possible application scenario of the embodiment of the present application;

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

fig. 2b is a schematic structural diagram of another coherent light receiving device provided in the present application;

fig. 3 is a schematic structural diagram of a possible coherent light receiving device according to an embodiment of the present disclosure;

FIG. 4 is a schematic diagram of a possible configuration of the coherent optical-electrical processor shown in FIG. 3;

fig. 5 is a schematic structural diagram of another possible coherent light receiving device provided in the embodiment of the present application;

fig. 6 is a schematic structural diagram of another possible coherent light receiving device provided in the embodiment of the present application;

fig. 7 is a schematic structural diagram of a fourth possible coherent light receiving device provided in the embodiment of the present application;

fig. 8 is a schematic structural diagram of a fifth possible coherent light receiving device according to an embodiment of the present disclosure;

fig. 9 is a schematic structural diagram of a sixth possible coherent light receiving device provided in the embodiment of the present application;

fig. 10a is a schematic flowchart of a coherent light receiving method according to an embodiment of the present application;

fig. 10b is a schematic flowchart of another coherent light receiving method according to the embodiment of the present application.

Detailed Description

The device form and the application scenario described in the embodiment of the present application are for more clearly illustrating the technical solution of the embodiment of the present invention, and do not limit the technical solution provided by the embodiment of the present invention. As can be known to those skilled in the art, with the evolution of device morphology and the emergence of new scenarios, the technical solution provided in the embodiments of the present application is also applicable to similar technical problems.

It should be noted that the terms "first," "second," and the like in this application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments described herein are capable of operation in sequences not described in the present application. "and/or" is used to describe the association relationship of the associated objects, meaning that three relationships may exist. For example, a and/or B, may represent: a exists alone, A and B exist simultaneously, and B exists alone. Specific method steps in method embodiments may also be applied to the functional description of related components in apparatus embodiments.

The coherent light receiving technical scheme provided by the application can be applied to different network scenes, including but not limited to: backbone optical transmission network, optical access network, data center interconnection, short-distance optical interconnection, wireless service forward/backward transmission and the like. Specifically, the technical solution provided by the present application may be used for receiving-side equipment corresponding to the different networks, or an optical system including the receiving-side equipment.

Fig. 1a and fig. 1b are schematic diagrams of two possible application scenarios to which the embodiment of the present application is applicable.

Fig. 1a shows a homogeneous coherent optical transmission system 100. The system 100 includes a transmission-side apparatus 101 and a reception-side apparatus 102, and optical fibers 103a and 103b connecting these two apparatuses. The transmitting-side apparatus 101 includes a data input 1011, a laser 1012, an optical splitter 1013, and a modulator 1014. The light output from the laser 1012 is split into two by the beam splitter 1013. One of the signals is modulated by the modulator 1014 to obtain signal light loaded with service data, and the other is used as local oscillation light. The signal light and the local oscillation light generated by the transmitting-side device 101 are transmitted to the receiving-side device 102 through the optical fibers 103a and 103 b. The receiving-end apparatus 102 includes a coherent receiving device 1021 and a Digital Signal Processor (DSP) 1022. The former receives signal light and local oscillator light to realize coherent light reception; which processes the electrical signal output by the coherent optical receiver 1021 to obtain traffic data. Both the signal light and the local oscillator light are generated by the transmitting-side device. Accordingly, the system 100 is referred to as a homologous coherent optical transmission system. It should be noted that the signal light and the local oscillator light may also be transmitted through one optical fiber. It should be noted that the DSP 1022 may also be located in the coherent light receiving device 1021.

Fig. 1b shows a conventional coherent optical transmission system 200. The system 200 includes a transmission-side device 201, a reception-side device 202, and an optical fiber 203 connecting the two devices. The transmitting side device 201 includes a data input 2011, a laser 12012, and a modulator 2013. The light output by the laser 12012 is modulated by the modulator 2013 to obtain signal light loaded with service data; and then transmitted to the receiving end device 102 through the optical fiber 203. The receiving end apparatus 202 includes a laser 22022, a coherent receiving device 2021 and a DSP 2023. Among them, the laser 22022 and the laser 12012 of the transmission-side device need to keep the frequency the same or substantially the same to achieve coherent light reception. The laser 2022 and the coherent light receiving device 2021 are connected by an optical fiber. Like fig. 1a, the DSP 2023 may be located in the coherent optical receiver 2021.

In the scenario example of fig. 1a, if the local oscillator light is transmitted by using a common optical fiber, the polarization state of the local oscillator light may be randomly deflected. This may cause the coherent optical receiving device at the receiving end to fail to operate properly. Similarly, in the scenario example of fig. 1b, the laser 22022 also needs to be connected with the coherent light receiver 2021 through an optical fiber, and the same problem can exist. The polarization maintaining optical fiber with relatively high price is adopted, and under ideal conditions, the local oscillation light can be prevented from generating polarization state and then deflecting in transmission, so that the coherent light receiving device can be ensured to normally acquire service data. However, in the existing network, the optical fiber is inevitably subjected to squeezing, so that the polarization maintaining performance of the polarization maintaining optical fiber is degraded, and the performance of the coherent light receiving device is degraded (i.e., a data receiving error occurs). Therefore, the problem of random polarization state deflection of local oscillation light can be solved to a certain extent by adopting the polarization-maintaining optical fiber. However, this solution increases the cost of the coherent optical transmission system and the performance is not stable.

In order to solve the above-mentioned problems of the prior art, the present application provides a new coherent light receiving device. The coherent light receiving device has signal light and local oscillator light as input and electrical signal as output. The output electrical signal includes service data, and the final service data can be obtained by further processing the output electrical signal. Alternatively, if the coherent optical receiving device includes a DSP, its output is traffic data. The coherent light receiving device enables two beams of local oscillator light with basically the same power to be used for coherent receiving related processing through relatively accurate phase control of the local oscillator light, and effectively avoids the problem that the receiver cannot work normally due to random change of the polarization state of the local oscillator light. By adopting the coherent light receiving device, the coherent light transmission system can adopt a conventional optical fiber (namely, a non-polarization-maintaining optical fiber) to realize normal coherent light receiving. Compared with the scheme adopting the polarization maintaining optical fiber, the technical scheme provided by the application reduces the cost of the coherent light transmission system.

Fig. 2a is a schematic structural diagram of a coherent light receiving device provided in the present application. As shown in fig. 2a, the coherent light receiving device 300 includes two Polarization Beam Splitters (PBS) (301 and 302), two Polarization Rotators (PR) (303a and 303b), two Phase Shifters (PS) (304 and 305), a coupler 306, and a coherent photoelectric processor 307. Therein, the coherent optical-to-electrical processor 307 includes two mixers (3071 and 3072) and a photodetector 3073.

The components shown in fig. 2a may be integrated optical components and/or spatial optical components. In particular, all components are integrated optical components, such as: silicon, indium phosphide (InP), silicon nitride, and other optoelectronic integrated materials. As another example, some components may be integrated optics and the remainder spatial optics. Alternatively, all components are space-optical. The present application is not limited thereto. Correspondingly, the connection relationships in the drawings may represent direct or indirect physical connections, and may also represent spatial relationships (i.e., no physical connections). Connections may also be described as coupled. This is not a limitation of the present application. See the examples that follow for details.

The PBS 301 is used to perform polarization beam splitting on the signal light (shown as S in fig. 2 a) input to the coherent light receiving device 300, and output two signal lights. These two signal lights (hereinafter referred to as a first signal light and a second signal light, where the second signal light is shown as S in fig. 2)₂) Are orthogonal. The PBS 302 is used to split the local oscillator light (L shown in fig. 2 a) input to the coherent light receiving device 300 and output two local oscillator lights. The polarization states of the two local oscillator lights (hereinafter referred to as a first local oscillator light and a second local oscillator light) are orthogonal. The PBS may also be referred to as a polarization beam splitter, and splits the input light in a polarization state to obtain two beams of light with orthogonal polarization states. It should be noted that a beam of light may include two polarization states (hereinafter, referred to as an x-polarization state and a y-polarization state), where the x-polarization state and the y-polarization state are orthogonal to each other. That is, a light beam with a single polarization state (polarization state x) is rotated by the polarization state and becomes a light beam with a polarization state y.

The PR 303a is used to rotate the polarization of the first signal light and output a third signal light (shown as S in fig. 2 a)₁). It should be noted that the polarization rotation mentioned in this application refers to 90 degree rotation or 270 degree rotation. Thus, S₁Polarization state of (1) and (S)₂The polarization state of (a) is the same. It should be noted that the aforementioned degree of rotation may have a small deviation due to practical device process limitations. It should be understood that references herein to polarization state rotation include such rotations of approximately 90 degrees or 270 degrees.

The PS 304 is configured to perform phase control on the first local oscillation light, and output a third local oscillation light. Partial normal sum S of the third local oscillator light₂The polarization state of (a) is the same.

And the PS 305 and the PR 303b are respectively configured to perform phase control and polarization rotation on the second local oscillation light, and output a fourth local oscillation light. And the polarization state of the fourth local oscillator light is the same as that of the third local oscillator light. It should be noted that the positions of PS 305 and PR 303b in fig. 2a can be exchanged. That is, the local oscillation light output by the PBS 302 may be subjected to polarization rotation and then phase control. And vice versa. Compared with the latter specific implementation, the former specific implementation PR does not affect the phase control of the light beam, and can reduce the complexity of the phase control.

Note that when the PBS and PR are directly connected, a Polarization beam Splitter Rotator (PSR) device may be substituted. It should be understood that the structure of replacing PBS and PR with PSR belongs to the simple structure variant shown in fig. 2a and also belongs to the technical solution protected by the present application.

The coupler 306 is configured to split and combine the third local oscillator light and the fourth local oscillator light, and output a fifth local oscillator light and a sixth local oscillator light (shown as L in fig. 2a, respectively)₁And L₂). Specifically, the coupler 306 has a 2 × 2 structure, i.e., two inputs and two outputs. Alternatively, the coupler 306 may take other configurations, such as: 2 x 3 or 2 x 4 structures. The former has less differential loss than the latter. Sometimes, the 1 x 2 structure is also referred to as a coupler. In the present application, for clarity of description, a coupler having a single input port and a plurality of output ports is referred to as an Optical Splitter (OS). In particular, the coupler may be a waveguide coupler or a Multimode interferometer (MMI) coupler. Note that the beam splitter splits only an input light beam, and does not need to combine the light beams.

The PS 304 and PS 305 perform phase control on the first local oscillation light and the second local oscillation light so that L is₁And L₂The power difference of (2) is smaller than a preset value. Specifically, the preset value may be 0, that is, the power of the two local oscillator lights is required to be equal. Or, in order to tolerate a certain error, the preset value can be set to a smaller value according to actual needs.

Coherent photoelectric processor 307 for receiving S₁、S₂、L₁And L₂And performs mixing and photoelectric conversion to output a plurality of coherent electrical signals. The input signal of one mixer of the coherent photoelectric processor is a beam of local oscillator light and a beam of signal light with the same polarization state. As can be seen from the above description of FIG. 2a, S₁、S₂、L₁And L₂The polarization state of (a) is the same. This makes the coherent optical electrical processor 307 simpler to design. That is, coherenceThe mixer design in the opto-electronic processor 307 is relatively simple. Specifically, the polarization state may be an X polarization state or a Y polarization state. Thus, specifically, the input beam of the mixer 3071 is S₁And L₁The input beam of the mixer 3072 is S₂And L₂. Alternatively, the input light beam of the mixer 3071 may be S₁And L₂The input beam of the mixer 3072 is S₂And L₁。

As known to those skilled in the art, the coherent optical electrical processor 307 is a structure commonly used in the coherent optical technology, and is configured to receive two local oscillator beams and two signal beams, perform frequency mixing and optical-electrical conversion processing on the four beams, and output a plurality of electrical signals having a certain relationship for further obtaining service data subsequently. In particular, the coherent optoelectronic processor may output four or eight coherent electrical signals, or other numbers of coherent electrical signals. The specific structure of the coherent optical-electrical processor 307 shown in fig. 2a is merely an example. Those skilled in the art may implement coherent optical-electrical processors using other existing or new architectures, depending on the particular needs. It should be understood that the specific structure of the coherent optical electrical processor referred to in this application, as well as other variations that may be readily apparent to one skilled in the art, should be considered within the scope of the present application.

Fig. 2b is a schematic structural diagram of another coherent light receiving device provided in the present application. As shown in fig. 2b, the coherent light receiving device 400 includes two PBSs (301 and 302), two PRs (403 and 303b), two PSs (304 and 305), a coupler 306, and a coherent photoelectric processor 307. The coherent optical-electrical processor 307 specifically includes two mixers (3071 and 3072) and a photodetector 3073. Fig. 2b and fig. 2a include the same components, and the detailed functions of the related components can refer to the description of fig. 2, which is not repeated herein.

The main differences between fig. 2b and fig. 2a are: the position of one PR (PR 403) in fig. 2b is different from the position of PR (303a) in fig. 2 a. In the configuration shown in fig. 2b, the signal light S is split by the PBS 301 into Sx and Sy (subscript indicates polarization state) whose polarization states are orthogonal; one of the two local oscillator lights with the same polarization state output by the coupler 306 is subjected to polarization state rotation through the PR 403 to obtain Lx and Ly. Sx and Lx of the same polarization state enter mixer 3071, and Sy and Ly of the same polarization state enter mixer 3072. It should be noted that, in fig. 2b, the PS 304 and the PS 305 control the phases of the local oscillator lights, so that the power difference between the local oscillator lights input to the two mixers is smaller than a preset value. That is, the power difference between Lx and Ly is substantially the same.

The mixer according to the present application is an optical mixer for coherent optical communication. The mixer may be implemented by spatial optics or silicon optics, etc., as known to those skilled in the art. Such as MMI mixers, coupler array mixers, etc. Unless otherwise stated, the mixer used in the existing coherent optical communication and the new mixer realized later with the development of optical materials can be used in the coherent optical receiver proposed in the present application.

The coherent light receiving device shown in fig. 2a and 2b performs phase control on the two local oscillator lights, so that the optical powers of the local oscillator lights entering the two mixers are basically the same, thereby ensuring that even if the local oscillator light input into the coherent light receiving device changes in a random polarization state, the normal operation of the coherent light receiving device is not affected.

The embodiments of the present application will be described in further detail below based on the above-described common aspects related to coherent light receiving devices, with reference to more drawings. It should be noted that, unless otherwise specified, a specific description of a feature in one embodiment may also be applied to explain that other embodiments refer to the corresponding feature. For example, the description of the specific structure of the coherent optical-electrical processor in one embodiment may be applied to the corresponding coherent optical-electrical processor in the other embodiments. As another example, the specific implementation of the relative positions of PS and PR in one embodiment may be applied to the relative positions of both in other embodiments. Further, to clearly illustrate the relationship of components in different embodiments, the present application uses the same or similar reference numbers to identify functionally the same or similar components in different embodiments. It should be noted that, in the description of the embodiments of the apparatus in the present application, the description of the angle from the light beam flow direction is for more clearly describing the technical solution, and is not to be understood as a limitation on the apparatus itself.

For simplicity of illustration, the following embodiments are based on fig. 2a (i.e., a beam input mixer supporting a single polarization state). Those skilled in the art will appreciate that the following embodiments may also achieve coherent reception of light of mixed polarization states by simple modification (i.e., changing the position of PR). It should be understood that the foregoing embodiment variations also fall within the scope of the present application.

Fig. 3 is a schematic structural diagram of a possible coherent light receiving device according to an embodiment of the present disclosure. As shown in fig. 3, the coherent light receiving device 500 includes two PSRs (501 and 502), two PSs (304 and 305), a coupler 306, and a coherent photoelectric processor 503. Except for the PSR, the functions of the other components shown in fig. 3 are the same as those of the related components shown in fig. 2a, and are not described again here. In fig. 3, the

PSRs

501 and 502 are configured to perform polarization beam splitting on an input light beam to obtain two light beams with orthogonal polarization states, and then perform polarization rotation on one of the two light beams to output two light beams with the same polarization state. Specifically, the PSR 501 is configured to split the signal light into two signal lights with the same polarization state; the PSR 502 is configured to split the local oscillator light into two local oscillator lights with the same polarization state. The two local oscillator beams are subjected to phase control and coupling processing, and then input to the coherent optical electrical processor 503 together with the two signal beams. The coherent photoelectric processor 503 mixes and photoelectrically converts the four lights, and outputs four coherent electric signals (I1, Q1, I2, and Q2 shown in fig. 3). For the description of the coherent photoelectric processor 503, reference may be made to the description of the coherent photoelectric processor 307 in fig. 2a, which is not described herein again.

It should be noted that when the PSR is a device, the device may be made of integrated optical material or space optical material. Alternatively, all of the components shown in FIG. 3 may be integrated optical devices. The integrated optical device may specifically be fabricated from one or more materials of silicon, germanium, silicon dioxide, silicon nitride, group III-V, and the like. The components may then be connected by a single polarization state waveguide. The coherent light receiving device 500 has a small size and high stability. Alternatively, the PSR may be constituted by a combination of a plurality of devices. For example, the PSR 501 may consist of one PBS and one PR. In particular, the second type of PSR may be of integrated optical material or spatial optical material. The present application is not limited thereto.

It should be further noted that, similar to fig. 2b, the apparatus of this embodiment can also achieve coherent light reception in a single polarization state by adding PR. For example, by adding one PR to each optical path of a signal beam and a local oscillator beam. For another example, the PSR 501 may be replaced by a PBS, and then a PR may be added to the optical path of a local oscillator beam.

It should be noted that the positional relationship of the four electrical signals shown in fig. 3 is merely an example. The present application does not limit the output positional relationship of the four electrical signals in specific implementation.

Fig. 4 is a schematic diagram of a possible structure of the coherent photoelectric processor shown in fig. 3. In this example, the coherent opto-electronic processor 503 includes two mixers (3071 and 3072) and four balanced detectors (503a-503 d). A balanced detector is a device for performing photoelectric conversion. The photoelectric conversion device comprises two input ports and an output port, photoelectric conversion and differential processing can be carried out on two input lights, and an electric signal is output. In fig. 4, a total of four balanced detectors output four electrical signals for further signal processing.

Specifically, each mixer outputs four beams of light respectively; each two beams of light are input into a balanced detector. The balance detector performs photoelectric processing on the two beams of light and outputs an electric signal. Take mixer 3071 and PD 503a as an example. Signal light S₁And local oscillator light L₁Into the input of mixer 3071. The mixer 3071 mixes the two beams and outputs four beams. Two of the four beams enter the PD 503 a. The PD 503a performs photoelectric processing on the two beams of light and outputs I1. The generation process of the other electrical signals Q1, I2 and Q2 is similar and will not be described herein. It should be noted that the 4 balanced detectors in fig. 4 may also be replaced by 8 ordinary Photodetectors (PDs) and 4 differential circuits. Specifically, each balanced detector is replaced with 2 PDs and one differential circuit. Wherein the inputs of the 2 PDs receive two of the mixers respectivelyAn output light; the outputs of the 2 PDs are connected to two input ports of the differential circuit, respectively. The differential circuit performs differential processing on the electric signals output by the two PDs and outputs one electric signal. Alternatively, the 4 balanced detectors of fig. 4 may be replaced by a detector array to perform the photoelectric processing to obtain a set of correlated electrical signals.

The coherent light receiving device 500 shown in fig. 3 performs phase control on the two local oscillator lights, so that the optical powers of the local oscillator lights entering the two mixers are basically the same, thereby avoiding the problem that the coherent light receiving device cannot work normally due to the random polarization state change of the input local oscillator lights. In addition, when the integrated optical component is adopted, the coherent light receiving device 500 has advantages of small volume and high stability.

Fig. 5 is a schematic structural diagram of another possible coherent light receiving device provided in the embodiment of the present application. As shown in fig. 5, the coherent light receiving device 600 includes two PBSs (601 and 604), two prss (602 and 606), two PSs (604 and 607), two mirrors (609a and 609b), a coupler 608, and a coherent photoelectric processor 603. The functional description of the other components, except for the

mirrors

609a and 609b, can be referred to the description of fig. 2a and will not be repeated here. In this embodiment, all the components of the coherent light receiving device 600 are spatial optical components. Thus, the arrows shown in FIG. 4 are directions of light beams and are not directly or indirectly physically connected. And mirrors 609a and 609b for reflecting the incident light so that the light beam output from the PBS can be incident into the coherent photoelectric processor 603 via the mirrors. In particular, the mirror may be a reflective flat mirror or a reflector mirror.

Optionally, the coherent light receiver 600 further includes one or more mirrors to implement the optical path change, and enter the appropriate components for corresponding processing according to the specific design requirement. The present application is not limited thereto.

Optionally, the coherent light receiving device 600 further comprises a polished or plated optical antireflection film. For example, it may be provided on the input side or the output side of the coherent light receiving device 600. The anti-reflection film can improve the light transmittance, so that the performance of the coherent light receiver is improved.

Optionally, the coherent light receiving device 600 further includes a lens. For example, a lens may be placed before the PBS. The lens can realize light beam focusing and improve the light transmission performance.

It should be noted that all the other components shown in fig. 5 can be implemented by using space optics mature in the art, and are not described in detail here. For example, the coupler may be implemented by parallel mirrors and transmission mirrors.

The coherent light receiving device 600 shown in fig. 5 performs phase control on the two local oscillator lights, so that the optical powers of the local oscillator lights entering the two mixers are basically the same, thereby avoiding the problem that the coherent light receiving device cannot work normally due to the random polarization state change of the input local oscillator lights. In addition, the coherent light receiving device 600 adopts all spatial optical components, and has a simple process and a lower cost than an integrated optical mode.

Fig. 6 is a schematic structural diagram of another possible coherent light receiving device according to an embodiment of the present disclosure. As shown in fig. 6, the coherent optical receiver 700 includes a coherent optical receiver 300 and a Digital Signal Processor (DSP) 701. That is, the coherent light receiving device may optionally further include a DSP. Here, the coherent light receiving device 300 may be replaced with the coherent light receiving device 400, the coherent light receiving device 500, or the coherent light receiving device 600 in the foregoing embodiments, and modifications of these devices described above.

The DSP 701 and the coherent optical receiver 300 have two connections. One is a connection 702 for inputting the output signal of the coherent optical receiving device 300 into the DSP 701. For example, a plurality of coherent electrical signals output from the coherent light receiving device 300 are input to the DSP 701. The DSP 701 can process the coherent electrical signals to obtain final service data. Alternatively, a detection signal output from the coherent light receiving device may also be input to the DSP 701. Reference is made in particular to the introduction relating to fig. 7. The other connection is a connection 703 for inputting a phase control signal of the DSP 701 to the coherent optical receiving apparatus 300 to realize phase control of the two PSs.

It should be noted that the number of the above-mentioned connections may be one or more. For example, four coherent electrical signals output from the coherent light receiving device 300. As another example, the control signal for the DSP 701 is one. It should be noted that the present application does not limit the number of DSPs used in fig. 6. For example, one DSP may be used to perform all functions, including in particular electrical signal processing to obtain traffic data and PS phase control. Alternatively, two or more DSPs may be used to perform both of the aforementioned functions.

The coherent light receiving device 700 shown in fig. 6 performs phase control on the two local oscillator lights, so that the optical powers of the local oscillator lights entering the two mixers are substantially the same, thereby avoiding the problem that the coherent light receiving device cannot work normally due to the random polarization state change of the input local oscillator lights. In addition, the coherent light receiving device 700 shown in fig. 6 integrates a DSP, and can provide better system stability than a scheme in which the coherent light receiving device 300 and the DSP are provided by two manufacturers, respectively.

The control procedure for the two PSs is further described below in connection with further embodiments. Three different examples are given in fig. 7 to 9.

Fig. 7 is a schematic structural diagram of a fourth possible coherent light receiving device according to an embodiment of the present application. As shown in fig. 7, the coherent optical receiver 900 specifically includes a coherent optical receiver 800, a DSP 1901, and a DSP 2902. Therein, the coherent light receiving device 800 includes two PSRs (501 and 502), two PSs (304 and 305), a coupler 306, a coherent photoelectric processor 503, and four OSs (801 and 804). The descriptions of the other components of the coherent light receiving device 800 except for the four OSs refer to the description of the device shown in fig. 3, and are not repeated herein. The coherent light receiving device 800 is mainly different from the device shown in fig. 3 in that the former has four more OSs. The four OSs tap off a portion of the light from two inputs and two outputs of coupler 306, respectively. The four split lights are input to the DSP 2902. The DSP2902 determines the phase adjustment magnitudes of the two PS (304 and 305) from the four beams of light. The DSP 1901 receives and processes four coherent electrical signals output by the coherent optical receiver 800 to obtain service data.

Specifically, as known to those skilled in the art, the four beams of light output by the OS 801-804 are subjected to photoelectric conversion and then input into the DSP. For example, the PD is used to convert the optical beam into an electrical signal (e.g., photocurrent). Optionally, the signal may be further amplified and then input to the DSP. For example, amplification is performed using a Trans-Impedance Amplifier (TIA).

In order to reduce the influence on the coherent reception processing, the split ratios of the four OSs are recommended to be controlled to a higher ratio. For example: 95:5, 90:10. That is, a higher proportion of the beam energy enters the mixer and less light enters DSP2902 for phase control.

Optionally, the split ratios of the four OSs are the same. Doing so may reduce the complexity of DSP2902 in calculating the phase control value.

The modifications of the coherent light receiving device in fig. 3 and the modifications in fig. 2b are applied to the coherent light receiving device 800 in fig. 7.

In the following, an exemplary phase control algorithm for calculating PS by DSP2902 will be described.

A simpler approach is to monitor the change in optical power of the four OS outputs by varying the amplitude of the two PS multiple times. The DSP2902 selects phase control values in which the powers of two local oscillator lights input to the coherent optical-electrical processor can be made the same or substantially the same, and applies corresponding control values to the two PSs. This approach is relatively simple. This method can be employed without strict requirements on the control time.

Another way is to obtain the phase adjustment amplitude of the PS more accurately by theoretical calculation. The photocurrents input to the DSP2902 by the four OSs are i₁，i₂，i₃，i₄For example. They can be represented as:

i₁＝K|E_Y|²＝K|E₀|²sin²θ

(1)

i₂＝K|E_X|²＝K|E₀|²cos²θ

(2)

wherein K is a fixed constant. And theta is the polarization angle of the input local oscillator light. Ex is the complex amplitude of the local oscillator light output by the OS 802. Ey is the complex amplitude of the local oscillator light output by the OS 801. LO1 is the complex amplitude of the local oscillator light output by OS 804. LO2 is the complex amplitude output by OS 803. j is a complex symbol. E₀Is the complex amplitude of the local oscillator light of the coherent optical receiver,

the current phase difference between Ex and Ey.

Using equations (1) - (4) above, one can solve:

the two input local oscillator lights input into the coherent photoelectric processor are required to have equal power, which is equivalent to the requirement that i3 is equal to i 4. That is, it is necessary to adjust the phase control amplitude of the PS to change

Thereby making the aforementioned object attained. In general, the phase characteristics of the PS are known. Then, with the second calculation method, one of the two PS can be changed once or at most twice to complete the phase control, so as to achieve that the power difference between the two beams output by the coupler is smaller than the preset value. For example, by applying a phase to the PS 305

If i3 is detected to be equal to i4, it indicates that the phase control is complete. Alternatively, by applying a phase to the PS 305

If calculated to obtain a new one

The larger the size, the wrong direction of adjustment is indicated. Reverse again to apply phase to the PS 305

The phase control can be completed by the adjustment. The second way can accomplish PS control faster by obtaining a more accurate control value through calculation.

Of course, the above two methods can also be used in combination. It should be noted that, of the four OSs in fig. 7,

OS

801 and 802 are optional. That is, the optical power monitoring can be done by only the OS 803 and 804 to accomplish the purpose of PS phase control.

It should also be noted that the phase adjustment can be accomplished by controlling only one of the two PSs. This approach is relatively simple. Alternatively, two beams of local oscillator light with substantially equal output power may be realized by adjusting the phase values of two PS simultaneously.

The coherent light receiving device shown in fig. 7 performs phase control on the two local oscillator lights, so that the optical powers of the local oscillator lights entering the two mixers are basically the same, thereby avoiding the problem that the coherent light receiving device cannot work normally due to the random polarization state change of the input local oscillator lights. In addition, the coherent light receiving device 800 shown in fig. 7 uses the optical splitter to directly split a partial light beam from the local light input to the mixer to perform optical power monitoring, thereby improving the accuracy of PS control.

Fig. 8 is a schematic structural diagram of a fifth possible coherent light receiving device according to an embodiment of the present application. As shown in fig. 8, the coherent light receiving device 1000 specifically includes a coherent light receiving device 400, a DSP 1901, and a DSP 21001. Fig. 8 does not show a complete structure of the coherent light receiving device 400, and specifically, refer to the structure shown in fig. 2 b. The difference between fig. 8 and fig. 7 is that the DSP 21001 determines the phase control values of the PS 304 and the PS 305 based on the four output electrical signals of the coherent light receiving device 400 as inputs.

Fig. 9 is a schematic structural diagram of a sixth possible coherent light receiving device according to an embodiment of the present application. As shown in fig. 9, the coherent light receiving apparatus 1100 specifically includes a coherent light receiving apparatus 400, a DSP 1901, and a DSP 21101. Fig. 9 does not show a complete structure of the coherent light receiving device 400, and specifically, refer to the structure shown in fig. 2 b. Fig. 9 and 8 differ in that the DSP 21101 determines the phase adjustment amplitude of the PS 304 and the PS 305 from two of the four output electrical signals of the coherent optical receiver 400 as inputs. Specifically, the two signals may be I1 and I2, I1 and Q2, Q1 and I2, or Q1 and Q2.

Fig. 8 and 9 may use the first approach described above to complete the phase adjustment. Specifically, the phases of the two PSs are adjusted a plurality of times, and then the optimum adjustment value is determined from the power difference of the electric signals input to the DSP. It should be noted that the coherent light receiving device 400 in fig. 8 and 9 may be replaced with the modified structure in the other embodiments described above. For example, 300 of fig. 2 a.

The two coherent optical receiving apparatuses (1000 and 1100) shown in fig. 8 and 9 perform PS phase control by using (all or part of) the output signals of the coherent optical-electrical processor so that the local oscillator optical powers input to the mixers are substantially the same, thereby ensuring continuous normal operation of the coherent optical receiving apparatuses. By using an electrical signal, both of these structures are simple in design.

It is noted that the materials of

components

800 and 400 in the example structures of fig. 7-10 include, in particular, integrated optical materials and/or spatial optical materials.

Fig. 10a is a schematic flowchart of a coherent light receiving method according to an embodiment of the present application. As shown in fig. 10a, the method comprises the following steps.

Step 1301, performing polarization beam splitting on signal light input into a coherent light receiving device to obtain first signal light and second signal light with orthogonal polarization states;

step 1302, performing polarization rotation on the first signal light to obtain a third signal light;

step 1303, performing polarization beam splitting on the local oscillation light input into the coherent light receiving device to obtain a first local oscillation light and a second local oscillation light with orthogonal polarization states;

step 1304, performing polarization rotation on the first local oscillation light to obtain a third local oscillation light;

step 1305, performing phase control on the third local oscillator light and the fourth local oscillator light, and then performing coupling processing on the third local oscillator light and the fourth local oscillator light to obtain fifth local oscillator light and sixth local oscillator light, where the phase control is performed on the third local oscillator light and the fourth local oscillator light so that a power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value;

step 1306, after performing frequency mixing and photoelectric conversion on the first signal light, the third signal light, the fifth local oscillator light, and the sixth local oscillator light, outputting a plurality of coherent electrical signals.

Specifically, the phase control of the third local oscillator light and the fourth local oscillator light may be implemented in various ways, so that a power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value. In one possible implementation, the phase control values for the third and fourth local oscillator lights may be determined from a plurality of coherent electrical signals. In another possible implementation, the aforementioned object may be achieved based on a fraction of the plurality of coherent electrical signals. In yet another possible implementation, the foregoing object may be achieved by splitting a small number of light beams from each of the third to sixth local oscillation lights, or splitting only a part of the light beams from the fifth and sixth local oscillation lights. In particular, reference may be made to the description of fig. 7-9, which is not repeated here.

Optionally, other processing may be performed on the local oscillator light and the signal light. For example, the light beam may be focused, and/or reflected. In addition, the order of the polarization rotation and the phase control for the first local oscillation light may be replaced by performing the phase control first and then performing the polarization rotation.

Fig. 10b is a schematic flowchart of a coherent light receiving method according to an embodiment of the present application. As shown in fig. 10b, the method comprises the following steps.

1401, performing polarization beam splitting on signal light input to a coherent light receiving device to obtain first signal light and second signal light of orthogonal polarization states, and performing polarization beam splitting on local oscillator light input to the coherent light receiving device to obtain first local oscillator light and second local oscillator light of orthogonal polarization states;

step 1402, performing polarization rotation on the first local oscillation light to obtain a third local oscillation light;

step 1403, performing phase control on the third local oscillator light and the fourth local oscillator light, and then performing coupling processing on the third local oscillator light and the fourth local oscillator light to obtain fifth local oscillator light and sixth local oscillator light, where the phase control is performed on the third local oscillator light and the fourth local oscillator light so that a power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value;

step 1404, performing polarization rotation on the fifth local oscillation light to obtain a seventh local oscillation light;

step 1405, after mixing and photoelectrically converting the first signal light, the second signal light, the fifth local oscillator light, and the seventh local oscillator light, outputting a plurality of coherent electrical signals.

The method shown in fig. 10a and the method shown in fig. 10b mainly differ in that: FIG. 10a shows four beams (two signal beams and two local oscillator beams) in a single polarization state when mixed; while the light beam when mixed in fig. 10b is four light beams in mixed polarization states (one signal light and one local oscillator light in the same polarization state, and the other signal light and the other local oscillator light in the same polarization state). Other processing procedures and optional steps are basically the same and are not described in detail herein.

By the processing of either of the above two methods, the local oscillator light can be processed into two polarized lights with substantially the same power, and then the frequency mixing processing is performed. The methods may be applied in a coherent light receiving device or an apparatus or system comprising a coherent light receiving device. The methods ensure that the performance of the coherent light receiving device is not influenced by the random change of the polarization state of the local oscillator light and always works normally.

The embodiment of the application also provides a receiving side device. The receiving side equipment comprises the coherent light receiving device provided by any device embodiment. Specifically, the receiving-side device may further include other components such as a DSP, a TIA, an Analog Digital Converter (ADC), and the like, for further processing the electrical signal output by the coherent optical receiver.

The embodiment of the application also provides a coherent light transmission system. The system comprises a transmitting side device, an optical fiber and a receiving side device comprising the coherent light receiving device given by any device embodiment described above. Specifically, the laser generating the local oscillation light may be in the transmitting-side device or in the receiving-side device. The optical fiber is used to connect the transmitting-side and receiving-side devices.

It should be noted that the above mentioned DSP is a processor. The DSP may also be replaced with other types of processors, according to particular needs. Such as a general purpose processor, an application specific integrated circuit, a field programmable gate array or other programmable logic device, discrete gate or transistor logic, discrete hardware components. A general purpose processor may be a microprocessor or any conventional processor or the like. Program code executed by the DSP to implement the aforementioned calculation of the phase control adjustment value may be stored in the memory. The memory may be a nonvolatile memory such as a Hard Disk Drive (HDD) or the like, and may also be a volatile memory (RAM) such as a random-access memory (RAM).

Finally, it should be noted that: 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. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A coherent light receiving device comprising a first Polarization Beam Splitter (PBS), a second PBS, a first Polarization Rotator (PR), a second PR, a first Phase Shifter (PS), a second PS, a coupler, and a coherent optical electrical processor, wherein:

the first PBS is used for carrying out polarization beam splitting on the signal light input into the coherent light receiving device and outputting first signal light and second signal light with orthogonal polarization states;

the first PR is configured to perform polarization rotation on the first signal light and output third signal light, where a polarization of the third signal light is the same as a polarization of the second signal light;

the second PBS is used for performing polarization beam splitting on the local oscillation light input into the coherent light receiving device and outputting first local oscillation light and second local oscillation light with orthogonal polarization states;

the first PS is configured to perform phase control on the first local oscillator light and output third local oscillator light, where a polarization state of the third local oscillator light is the same as a polarization state of the second signal light;

the second PS and the second PR are respectively configured to perform phase control and polarization rotation on the second local oscillation light, and output fourth local oscillation light, where a polarization state of the fourth local oscillation light is the same as a polarization state of the third local oscillation light;

the coupler is used for splitting and combining the third local oscillator light and the fourth local oscillator light and outputting fifth local oscillator light and sixth local oscillator light;

the first PS and the second PS perform phase control on the first local oscillation light and the second local oscillation light so that the power difference between the fifth local oscillation light and the sixth local oscillation light is smaller than a preset value;

and the coherent photoelectric processor is configured to receive the second signal light, the third signal light, the fifth local oscillator light and the sixth local oscillator light, perform frequency mixing and photoelectric conversion, and output a plurality of coherent electrical signals.

2. The coherent optical receiving device according to claim 1, wherein the second PS and the second PR are respectively configured to perform phase control and polarization rotation on the second local oscillation light, and output a fourth local oscillation light, specifically comprising:

the second PS is configured to perform phase control on the second local oscillation light and output a seventh local oscillation light, and the second PR is configured to perform polarization rotation on the seventh local oscillation light and output a fourth local oscillation light; or,

the second PR is configured to perform polarization rotation on the second local oscillation light and output eighth local oscillation light, and the second PS is configured to perform phase control on the eighth local oscillation light and output the fourth local oscillation light.

3. The coherent optical receiver according to any one of claims 1 to 2, further comprising a first Optical Splitter (OS), a second OS, a third OS, and a fourth OS, wherein the first OS to the fourth OS are respectively configured to separate ninth to twelfth local oscillator lights from the third local oscillator light to the sixth local oscillator light, and the ninth to twelfth local oscillator lights are configured to determine phase adjustment amplitudes of the first PS and the second PS.

4. The coherent light receiving device according to claim 3, wherein splitting ratios of the first OS to the fourth OS are the same.

5. The coherent optical receiving device according to any of claims 1 to 2, further comprising a fifth Optical Splitter (OS) and a sixth OS, wherein the fifth OS and the sixth OS are respectively configured to split a thirteenth local oscillator light and a fourteenth local oscillator light from the fifth local oscillator light to the sixth local oscillator light, and the thirteenth local oscillator light and the fourteenth local oscillator light are configured to determine phase adjustment amplitudes of the first PS and the second PS.

6. The coherent light receiving device according to claim 5, wherein a splitting ratio of the fifth OS and the sixth OS is the same.

7. A coherent light receiving device according to any one of claims 1 to 6, wherein all components of the coherent light receiving device are integrated optical components.

8. The coherent light receiving device according to any one of claims 1 to 6, wherein all components of the coherent light receiving device are spatial optical components, the coherent light receiving device further comprising a first reflecting mirror and a second reflecting mirror, wherein:

the first reflector is used for reflecting the first signal light, so that the first PR rotates the polarization state of the reflected first signal light;

the second reflector is configured to reflect the second local oscillation light, so that the second PS and the second PR perform phase control and polarization rotation on the reflected second local oscillation light.

9. The coherent optical receiving device according to any one of claims 1 to 2, further comprising a Digital Signal Processor (DSP) for phase-adjusting the first PS and the second PS.

10. The coherent optical receiver according to claim 3 or 4, further comprising another Digital Signal Processor (DSP) configured to receive the ninth to twelfth local oscillator lights, determine phase adjustment amplitudes of the first and second PSs according to the ninth to twelfth local oscillator lights, and perform phase adjustment on the first and second PSs using the phase adjustment amplitudes.

11. The coherent optical receiver according to claim 9, wherein the DSP performs phase adjustment only for one of the first PS and the second PS, so that a power difference between the fifth local oscillation light and the sixth local oscillation light is smaller than a preset value.

12. The coherent optical receiver according to claim 9 or 11, wherein the DSP is configured to perform phase adjustment on the first PS and the second PS, and specifically includes:

and the DSP determines the phase adjustment amplitude of the first PS and the second PS according to the multi-path coherent electric signal, so that the power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value.

13. The coherent optical receiver according to claim 9 or 11, wherein the DSP is configured to perform phase adjustment on the first PS and the second PS, and specifically includes:

and the DSP determines the phase adjustment amplitude of the first PS and the second PS according to part of the electric signals of the multi-path coherent electric signals, so that the power difference between the fifth local oscillator light and the sixth local oscillator light is smaller than a preset value.

14. A coherent optical receiving device according to any of claims 9 and 11-13, wherein the DSP is further configured to process the plurality of coherent electrical signals to obtain traffic data.

15. A coherent optical receiving device, comprising the coherent optical receiving apparatus according to any one of claims 1 to 14, wherein the coherent optical receiving device receives the local oscillator light; or, the coherent light receiving device generates the local oscillation light.

16. An optical system comprising an optical transmitting apparatus, an optical fiber, and the coherent optical receiving apparatus of claim 15, which receives the signal light transmitted by the optical transmitting apparatus through the optical fiber; the receiving, by the coherent light receiving device, the local oscillator light or the local oscillator light generated by the coherent light receiving device specifically includes:

the coherent light receiving device receives the local oscillator light sent by the sending device through the optical fiber; or, the coherent light receiving device generates the local oscillation light.

17. A coherent light receiving device comprising a first Polarization Beam Splitter (PBS), a second PBS, a first Polarization Rotator (PR), a second PR, a first Phase Shifter (PS), a second PS, a coupler, and a coherent optical electrical processor, wherein:

the first PS is configured to perform phase control on the first local oscillation light and output third local oscillation light;

the second PS and the first PR are respectively configured to perform phase control and polarization rotation on the second local oscillation light and output fourth local oscillation light;

the second PR is used for rotating the polarization state of the fifth polarized light and outputting seventh local oscillation light;

the first PS and the second PS perform phase control on the first local oscillation light and the second local oscillation light, so that the power difference between the seventh local oscillation light and the sixth local oscillation light is smaller than a preset value;

the coherent photoelectric processor is configured to receive the first signal light, the second signal light, the sixth local oscillator light, and the seventh local oscillator light, perform frequency mixing and photoelectric conversion, and output a plurality of coherent electrical signals.

18. The coherent optical receiver according to claim 17, further comprising a first Optical Splitter (OS), a second OS, a third OS, and a fourth OS, wherein the first OS to the fourth OS are respectively configured to separate eighth to eleventh local oscillator light from the third local oscillator light, the fourth local oscillator light, the sixth local oscillator light, and the seventh local oscillator light, and the eighth to eleventh local oscillator light is configured to determine phase adjustment amplitudes of the first PS and the second PS.

19. The coherent light receiving device according to claim 18, wherein the splitting ratios of the first OS to the fourth OS are the same.