Optoelectronic receiving device, receiving method and coherent receiver of a coherent receiver

Abstract

The present disclosure relates to an optoelectronic receiving device, a receiving method, and a coherent receiver for a coherent receiver. The optoelectronic receiving device includes: a local oscillator light generation module configured to generate dual-wavelength orthogonally polarized local oscillator light; a coupling module configured to perform coherent coupling on received signal light and the dual-wavelength orthogonally polarized local oscillator light and output dual-wavelength coherent light; and an optoelectronic detection module configured to convert the dual-wavelength coherent light output by the coupling module into an electrical signal and output the electrical signal. The technical solution of the present disclosure can reduce the number of optical devices in the coherent receiver and lower the cost.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communication, and particularly to an optical and electrical receiving device, a receiving method and a coherent receiver of a coherent receiver. Background Art

[0002] In the field of optical fiber communication, with the development of data and voice services, especially the rapid development of video and multimedia services, the demand for the bandwidth of telecommunication networks is continuously increasing. From the perspective of the mainstream development trend, coherent technology will be gradually applied to access network systems.

[0003] Figure 1 It is a coherent detection system based on phase diversity and polarization diversity. After the signal light is input into the polarization coupling beam splitting device, first, the x-direction linearly polarized light and the y-direction linearly polarized light are formed through the polarization beam splitter. The x-direction and y-direction linearly polarized lights are respectively divided into two optical signals through the corresponding couplers, that is, the first signal light in the x direction, the second signal light in the x direction, the first signal light in the y direction, and the second signal light in the y direction are generated. After the local oscillator light generated by the local oscillator is input into the polarization coupling beam splitting device, first, the x-direction linearly polarized light and the y-direction linearly polarized light are formed through the polarization beam splitter. The x-direction and y-direction linearly polarized lights are respectively divided into two optical signals through the corresponding couplers, that is, the first local oscillator light in the x direction, the second local oscillator light in the x direction, the first local oscillator light in the y direction, and the second local oscillator light in the y direction are generated.

[0004] Figure 1 In [reference], the signal light and the local oscillator light in the same polarization state are subjected to optoelectronic detection through the balanced receiving device to output the photocurrent. Among them, the first signal light in the x direction and the first local oscillator light in the x direction after a 90-degree phase shift generate the first photocurrent after the coupled coherent balanced detection by the first coherent balanced receiving device. The second signal light in the x direction and the second local oscillator light in the x direction generate the second photocurrent after the coupled coherent balanced detection by the second coherent balanced receiving device. The first signal light in the y direction and the first local oscillator light in the y direction after a 90-degree phase shift generate the third photocurrent after the coupled coherent balanced detection by the third coherent balanced receiving device. The second signal light in the y direction and the second local oscillator light in the y direction generate the fourth photocurrent after the coupled coherent balanced detection by the fourth coherent balanced receiving device. Then, the first photocurrent, the second photocurrent, the third photocurrent, and the fourth photocurrent are processed by the subsequent DSP (Digital Signal Processing) to recover the signal.

[0005] In the above-mentioned coherent detection system based on phase diversity and polarization diversity, due to the large number of optical devices, complex architecture, and high cost, the popularization of the coherent detection system is limited. Summary of the Invention

[0006] The present invention provides an optical and electrical receiving device, a receiving method and a coherent receiver for a coherent receiver, which can reduce the number of optical devices of the coherent receiver and lower the cost.

[0007] According to the first aspect of the present application, an optical and electrical receiving device for a coherent receiver provided by an embodiment of the present invention includes:

[0008] A local oscillator light generation module for generating dual-wavelength orthogonally polarized local oscillator light;

[0009] A coupling module for coherently coupling the received signal light and the dual-wavelength orthogonally polarized local oscillator light and outputting dual-wavelength coherent light;

[0010] An optoelectronic detection module for converting the dual-wavelength coherent light output by the coupling module into an electrical signal and then outputting it.

[0011] According to the second aspect of the present application, an embodiment of the present invention provides a coherent receiver, including:

[0012] The above-mentioned optical and electrical receiving device and a demodulation module;

[0013] The demodulation module is configured to demodulate the electrical signal output by the optical and electrical receiving device.

[0014] According to the third aspect of the present application, an embodiment of the present invention provides a receiving method for a coherent receiver, including:

[0015] Coherently coupling the signal light and the dual-wavelength orthogonally polarized local oscillator light to generate dual-wavelength coherent light;

[0016] Converting the dual-wavelength coherent light into an electrical signal and then outputting it.

[0017] Compared with the related art, an optical and electrical receiving device, a receiving method and a coherent receiver for a coherent receiver provided by an embodiment of the present invention can reduce the number of optical devices of the coherent receiver and lower the cost by coherently coupling the signal light and the dual-wavelength orthogonally polarized local oscillator light to generate dual-wavelength coherent light, converting the dual-wavelength coherent light into an electrical signal and then outputting it. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a coherent detection system based on phase diversity and polarization diversity in the prior art;

[0019] Figure 2 It is a schematic diagram of an optical and electrical receiving device for a coherent receiver according to Embodiment 1 of the present invention;

[0020] Figure 3 It is a schematic diagram of a coherent receiver according to Embodiment 2 of the present invention;

[0021] Figure 4 Flowchart of the receiving method of a coherent receiver according to Embodiment 3 of the present invention;

[0022] Figure 5 Schematic diagram of a coherent receiver according to Example 1 of the present invention;

[0023] Figure 6 Schematic diagram of the wavelength relationship between the local oscillator light and the signal light in Example 1 of the present invention;

[0024] Figure 7 Schematic diagram of the optoelectronic receiving device of a coherent receiver according to Example 2 of the present invention. Detailed implementation manners

[0025] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined arbitrarily with each other.

[0026] The steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And, although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0027] Embodiment 1

[0028] As Figure 2 shown, the embodiment of the present invention provides an optoelectronic receiving device of a coherent receiver, including:

[0029] A local oscillator light generation module 10, configured to generate dual-wavelength orthogonally polarized local oscillator light;

[0030] A coupling module 20, configured to perform coherent coupling on the received signal light and the dual-wavelength orthogonally polarized local oscillator light and output dual-wavelength coherent light;

[0031] An optoelectronic detection module 30, configured to convert the dual-wavelength coherent light output by the coupling module into an electrical signal and then output it;

[0032] In one implementation manner, the dual-wavelength orthogonally polarized local oscillator light is two mutually independent local oscillator lights with orthogonal polarization directions; or; the dual-wavelength orthogonally polarized local oscillator light is the local oscillator light after combining two local oscillator lights with orthogonal polarization directions through a polarization beam combiner; wherein, the two local oscillator lights with orthogonal polarization directions have different wavelengths;

[0033] In one implementation manner, the dual-wavelength orthogonally polarized local oscillator light includes a first local oscillator light and a second local oscillator light, wherein, the wavelength λ of the first local oscillator light 1 and the wavelength λ of the signal light sare not equal, and the wavelength λ of the second local oscillator light 2 and the wavelength λ of the signal light s are not equal, and satisfy the following condition: |λ 1 - λ s | ≠ |λ 2 - λ s |;

[0034] In one embodiment, the coupling module includes:

[0035] an optical coupler or an optical mixer;

[0036] When the optical coupler or the optical mixer includes multiple inputs and multiple outputs, connect one of the multiple outputs to the photoelectric detection module;

[0037] In one embodiment, the photoelectric detection module includes: a PIN photodetector.

[0038] The photoelectric receiving device of this embodiment uses a single coupling module plus a single photoelectric detection module to coherently couple the local oscillator light and the signal light with mutually orthogonal dual-wavelength polarization states, and converts them into two intermediate-frequency signals with different frequencies through the photoelectric detection module. Since the information on the two orthogonal polarization states will not undergo coherent cancellation, polarization-insensitive reception is achieved. Compared with the four-channel coherent balanced receiver in the related art, the system architecture is simple, the implementation complexity of the optical path at the receiving end is low, and the cost is reduced.

[0039] Embodiment 2

[0040] As Figure 3 shown, an embodiment of the present invention provides a coherent receiver, including: a photoelectric receiving device 1 and a demodulation module 2;

[0041] The photoelectric receiving device 1 is the photoelectric receiving device described in Embodiment 1;

[0042] The demodulation module 2 is used to demodulate the electrical signal output by the photoelectric receiving device 1.

[0043] In one embodiment, the demodulation module is used to demodulate the electrical signal in the following manner:

[0044] Extract a first intermediate-frequency signal and a second intermediate-frequency signal with different frequencies from the electrical signal; wherein, the first intermediate-frequency signal is obtained by photoelectric conversion of the optical signal after coherent coupling of the first local oscillator light and the signal light, and the second intermediate-frequency signal is obtained by photoelectric conversion of the optical signal after coherent coupling of the second local oscillator light and the signal light;

[0045] Filter the first intermediate frequency signal and the second intermediate frequency signal respectively to obtain a first signal and a second signal; wherein, the first signal carries first polarization direction information, and the second signal carries second polarization direction information; the first polarization direction is orthogonal to the second polarization direction;

[0046] Perform digital signal processing on the first signal and the second signal to obtain received information;

[0047] In one embodiment, the signal light is a modulated signal; the modulation mode of the signal light includes any one of the following: amplitude modulation, phase modulation, amplitude-phase modulation, and high-order modulation;

[0048] Wherein, the high-order modulation includes: polarization multiplexing modulation.

[0049] The optoelectronic receiving device of the coherent receiver uses local oscillator light and signal light with orthogonally polarized states of two wavelengths for coherent coupling. After photoelectric conversion, two intermediate frequency signals with different frequencies can be obtained. The demodulation module obtains polarization diversity from the two intermediate frequency signals, and then performs digital signal processing on each intermediate frequency signal to obtain received information, realizing polarization-insensitive reception. Compared with the four-way coherent balanced receiver in the related art, the system architecture is simple, the implementation complexity of the optical path at the receiving end is low, and the cost is reduced.

[0050] Embodiment 3

[0051] As Figure 4 shown, the embodiment of the present invention provides a receiving method for a coherent receiver, including:

[0052] Step S110, coherently couple the signal light with the local oscillator light of two wavelengths with orthogonal polarization to generate two-wavelength coherent light;

[0053] Step S120, convert the two-wavelength coherent light into an electrical signal and output it;

[0054] In one embodiment, the local oscillator light of two wavelengths with orthogonal polarization is two independent local oscillator lights with orthogonal polarization directions; or; the local oscillator light of two wavelengths with orthogonal polarization is the local oscillator light after combining two local oscillator lights with orthogonal polarization directions through a polarization beam combiner; wherein, the two local oscillator lights with orthogonal polarization directions have different wavelengths;

[0055] In one embodiment, the local oscillator light of two wavelengths with orthogonal polarization includes a first local oscillator light and a second local oscillator light, wherein the wavelength λ 1 of the first local oscillator light is s not equal to the wavelength λ 2 of the signal light, and the wavelength λ s of the second local oscillator light is 1-λ s |≠| λ 2 -λ s |;

[0056] In one embodiment, the coherent coupling and output of the signal light and the dual-wavelength orthogonally polarized local oscillator light include:

[0057] Coherently coupling and outputting the signal light and the dual-wavelength orthogonally polarized local oscillator light through a coupler / optical mixer;

[0058] In one embodiment, the signal light is a modulated signal; the modulation method of the signal light includes any one of the following: amplitude modulation, phase modulation, amplitude-phase modulation, and higher-order modulation;

[0059] Among them, the higher-order modulation includes: polarization multiplexing modulation;

[0060] In one embodiment, the method further includes: demodulating the electrical signal;

[0061] In one embodiment, the demodulating of the electrical signal includes:

[0062] Extracting a first intermediate-frequency signal and a second intermediate-frequency signal with different frequencies from the electrical signal; wherein, the first intermediate-frequency signal is obtained by performing optoelectronic conversion on the optical signal after coherent coupling of the first local oscillator light and the signal light, and the second intermediate-frequency signal is obtained by performing optoelectronic conversion on the optical signal after coherent coupling of the second local oscillator light and the signal light;

[0063] Performing filtering processing on the first intermediate-frequency signal and the second intermediate-frequency signal respectively to obtain a first signal and a second signal; wherein, the first signal carries first polarization direction information, the second signal carries second polarization direction information; the first polarization direction and the second polarization direction are orthogonal to each other;

[0064] Performing digital signal processing on the first signal and the second signal to obtain received information.

[0065] Example 1

[0066] As Figure 5 shown, this example provides a coherent receiver, including an optoelectronic receiving device and a demodulation module. The optoelectronic receiving device includes: two local oscillator light sources, a coupling module, and an optoelectronic detection module.

[0067] Among them, the local oscillator light source is implemented by using a laser commonly used in the prior art (such as a directly modulated laser, an electro-absorption modulated laser, etc.). In Example 1, two local oscillator light sources are used, corresponding to local oscillator light 1 and local oscillator light 2 respectively. The optical wavelength output by local oscillator light 1 is λ 1 (λ 1 ≠ λs ), with a polarization state of T x mode; The optical wavelength output by the local oscillator light 2 is λ 2 (λ 2 ≠λ s ), with a polarization state of T y mode. It should be emphasized here that the polarization states between the two local oscillator lights emitted by the local oscillator light 1 and the local oscillator light 2 need to be orthogonal to each other, but the polarization states are not necessarily in the horizontal and vertical directions, but can be the polarization states corresponding to any two opposite points on the Poincaré sphere.

[0068] Among them, as Figure 6 shown, the wavelengths corresponding to the two local oscillator lights not only need to be distinguished from the signal light, but also need to satisfy |λ 1 -λ s |≠|λ 2 -λ s |, that is, the frequency offsets of the two local oscillator lights from the signal light are inconsistent (Δf 1 ≠Δf 2 ). The wavelengths of the two local oscillator lights can be distributed on the left side of the signal light wavelength at the same time, or can be distributed on both sides of the signal light wavelength respectively, or can be distributed on the right side of the signal light wavelength at the same time. It should be emphasized here that for the frequency offsets Δf 1 and Δf 2 , when selecting, the bandwidth parameters of subsequent optical devices and electrical devices, as well as the signal bandwidth of the signal source, can be referred to.

[0069] The local oscillator light in Example 1 uses a form of two wavelengths with orthogonal polarization states to replace the polarization diversity method in the related technology to achieve polarization-insensitive reception. The frequency offsets of the two local oscillator lights from the signal light are Δf 1 and Δf 2 . After passing through the optical multiplexing device (or mixing device) and the photodetector, two intermediate-frequency signals with different frequencies will be formed. The two intermediate-frequency signals with different frequencies can represent the information on the two orthogonal polarization states in the original signal light. The coherent reception device in Example 1 has a significant reduction in the complexity of the optical path and the number of devices compared with the coherent reception system in the related technology, so the cost of the receiver can be effectively reduced.

[0070] In the receiver of Example 1, the emitted optical wavelength of the local oscillator light 1 is λ 1 , and the polarization state is in the x direction; the emitted optical wavelength of the local oscillator light 2 is λ 2 , and the polarization is in the y direction, and the x direction and the y direction are orthogonal. The orthogonal polarization states of the two local oscillator lights can enable all polarization states of the signal light to be detected, and no coherent situation will occur between the two local oscillator lights.

[0071] Assume that the input signal light E after being transmitted through the optical fiber channel sis in an arbitrary polarization state. The optical field amplitude of the signal light can be decomposed into two polarization states in the x - direction and the y - direction;

[0072] The signal light E s is coherently coupled with the local oscillator light and the eigen - light respectively in an optical coupler.

[0073] The photocurrent after the coherent coupling and passing through the photodetector is:

[0074]

[0075] where A LO1 is the maximum amplitude of the local oscillator light 1, A LO2 is the maximum amplitude of the local oscillator light 2, A s is the maximum amplitude of the signal light, θ is the angle between the signal light and the x - polarization state direction, ω IF1 is the intermediate - frequency signal frequency after the signal light beats with the local oscillator light 1, ω IF2 is the intermediate - frequency signal frequency after the signal light beats with the local oscillator light 2; is the phase of the signal light, is the phase of the local oscillator light 1, is the phase of the local oscillator light 2.

[0076] In the above photocurrent I PD A s 2 is the square component of the small - signal light, A LO1 2 is the DC component of the local oscillator light 1, A LO2 2 is the DC component of the local oscillator light 2.

[0077] In the above photocurrent I PD the first two terms are the intermediate - frequency signal terms of two different frequencies that need to be recovered after coherence. Using two wavelengths can prevent the intermediate - frequency terms of the two different frequencies from canceling each other out in a single - path detector (thus resulting in inability to perform coherent detection).

[0078] The generated photocurrent I PD contains intermediate - frequency terms of two different frequencies. The intermediate - frequency signals of each frequency are filtered respectively to obtain the first signal and the second signal. Among them, the first signal carries the x - polarization direction information, and the second signal carries the y - polarization direction information.

[0079] Digital signal processing (DSP processing) is performed on the first signal and the second signal to obtain the final received information; among them, the received information refers to the electrical information carried on the optical carrier at the receiving end.

[0080] The coherent receiver in the above Example 1 has the following characteristics:

[0081] 1) Dual-wavelength realizes low-cost polarization-insensitive coherent reception.

[0082] The implementation method here is that the local oscillator light uses dual-wavelength orthogonally polarized light as input. After passing through the photodetector, the polarization information in the x and y directions is respectively converted into two intermediate-frequency signals with different frequencies. The dual-wavelength and orthogonal polarization states can prevent the cancellation of the two polarization information in one-way coherence. In this way, regardless of the polarization state of the signal light, it can perform coherent interference with at least one beam of local oscillator light, realizing polarization-insensitive reception.

[0083] 2) The receiver uses an optical coupling module with a single-port output, plus a single photodetection module, reducing the number of optical devices and realizing low-cost reception.

[0084] The optical coupling module here is not limited to an optical coupler / optical mixer with multiple inputs and a single output. It can also include an N×M optical coupler / optical mixer. The number of input ports N is determined according to the system architecture requirements, and only one of the output ports M can be used to connect to the photodetection device for coherent detection. There is no mandatory requirement for the number of input and output ports of the optical coupler / optical mixer.

[0085] 3) There is no mandatory requirement for the modulation method of the input signal. High-order modulation signals such as amplitude modulation signals, phase modulation signals, amplitude-phase modulation signals, and polarization multiplexing signals are all applicable to the coherent receiver of this application.

[0086] Compared with the related technology, the coherent receiver solution in this example, for polarization-insensitive reception, uses local oscillator light with dual-wavelength polarization states orthogonal to each other, so that in the case of one-way coherence in the coupling module, the information on the two orthogonal polarization states will not cancel each other out. This example uses a single coupling module plus a single photodetection module. Compared with the four-way coherent balanced receiver in the related technology, the system architecture is simple, the complexity of the optical path implementation at the receiving end is low, and the cost is reduced.

[0087] Example 2

[0088] As Figure 7 shown, this example provides a photoelectric receiving device for a coherent receiver. The photoelectric receiving device has made changes to the local oscillator light source in Example 1. In Example 2, the two-wavelength local oscillator light with orthogonal polarization generated originally is first combined into a beam of local oscillator light through a polarization beam combiner, and then combined and cohered with the signal light through a 2×1 optical coupler.

[0089] In Example 1, a 3×1 optical coupler is adopted. After the signal light, local oscillator light 1, and local oscillator light 2 pass through the optical coupler, the energy loss is 1 / 3 of the original. In Example 2, a 2×1 optical coupler is adopted, and only 3 dB attenuation is generated for both the signal light and the synthesized local oscillator light, which is less than that of the device in Example 1 in terms of optical energy loss.

[0090] For the local oscillator light generating device, a dual-polarization distributed Bragg feedback fiber laser can also be used. It should be emphasized here that any local oscillator light source capable of generating two wavelengths with two orthogonally polarized states can be used in the coherent receiver optoelectronic receiving device of the present application.

[0091] Regarding the coupling devices in Example 1 and Example 2, they are not limited to 3×1 or 2×1 optical couplers, and can also include optical mixers with multi-port input / output, such as 180°, 120°, 90° optical mixers, etc.

[0092] Those of ordinary skill in the art can understand that all or some of the steps in the methods disclosed above, and the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, and their appropriate combinations. In the hardware implementation, the division of the functional modules / units mentioned above does not necessarily correspond to the division of physical components; for example, a physical component can have multiple functions, or a function or step can be executed by several physical components in cooperation. Some physical components or all physical components can be implemented as software executed by a processor, such as a central processing unit, a digital signal processor, or a microprocessor, or be implemented as hardware, or be implemented as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include a computer storage medium (or non-transitory medium) and a communication medium (or transitory medium). As is well known to those of ordinary skill in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information, such as computer-readable instructions, data structures, program modules, or other data. The computer storage medium includes, but is not limited to, RAM, ROM, EEPROM, flash memory, or other memory technologies, CD-ROM, digital versatile disk (DVD), or other optical disk storage, magnetic cassette, tape, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, as is well known to those of ordinary skill in the art, the communication medium generally includes computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transmission mechanism, and can include any information delivery medium.

[0093] It should be noted that the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention. However, these corresponding changes and modifications should all fall within the protection scope of the appended claims of the present invention.

Claims

1. An optoelectronic receiving device for a coherent receiver, comprising: a local oscillator light generation module for generating dual-wavelength orthogonally polarized local oscillator light; a coupling module for coherently coupling the received signal light and the dual-wavelength orthogonally polarized local oscillator light and outputting dual-wavelength coherent light; an optoelectronic detection module for converting the dual-wavelength coherent light output by the coupling module into an electrical signal and outputting it; wherein the coupling module includes three inputs; the dual-wavelength orthogonally polarized local oscillator light includes a first local oscillator light and a second local oscillator light, wherein the wavelength λ1 of the first local oscillator light is not equal to the wavelength λs of the signal light, the wavelength λ2 of the second local oscillator light is not equal to the wavelength λs of the signal light, and the following condition is satisfied: |λ1 - λs| ≠ |λ2 - λs|.

2. The optoelectronic receiving device according to claim 1, characterized in that: the dual-wavelength orthogonally polarized local oscillator light is two mutually independent local oscillator lights with orthogonal polarization directions; or; the dual-wavelength orthogonally polarized local oscillator light is the local oscillator light after combining two local oscillator lights with orthogonal polarization directions through a polarization beam combiner; wherein, the two local oscillator lights with orthogonal polarization directions have different wavelengths.

3. The optoelectronic receiving device according to claim 1, characterized in that: the coupling module includes: an optical coupler or an optical mixer; when the optical coupler or the optical mixer includes multiple inputs and multiple outputs, connect one of the multiple outputs to the optoelectronic detection module.

4. A coherent receiver, comprising: the optoelectronic receiving device according to any one of claims 1-3 and a demodulation module; the demodulation module for demodulating the electrical signal output by the optoelectronic receiving device.

5. The coherent receiver according to claim 4, characterized in that: the signal light is a modulated optical signal; the demodulation module for demodulating the electrical signal output by the optoelectronic receiving device in the following manner: extracting a first intermediate frequency signal and a second intermediate frequency signal with different frequencies from the electrical signal; wherein, the first intermediate frequency signal is obtained by optoelectronic conversion of the optical signal after coherent coupling of the first local oscillator light and the signal light, and the second intermediate frequency signal is obtained by optoelectronic conversion of the optical signal after coherent coupling of the second local oscillator light and the signal light; performing filtering processing on the first intermediate frequency signal and the second intermediate frequency signal respectively to obtain a first signal and a second signal; wherein, the first signal carries first polarization direction information, the second signal carries second polarization direction information; the first polarization direction and the second polarization direction are orthogonal to each other; performing digital signal processing on the first signal and the second signal to obtain received information.

6. The coherent receiver according to claim 5, characterized in that: the modulation mode of the signal light includes any one of the following: amplitude modulation, phase modulation, amplitude-phase modulation, high-order modulation.

7. A receiving method for a coherent receiver, comprising: coherently coupling the received signal light and the dual-wavelength orthogonally polarized local oscillator light to generate dual-wavelength coherent light; converting the dual-wavelength coherent light into an electrical signal and outputting it; Among them, the dual-wavelength orthogonally polarized local oscillator light includes a first local oscillator light and a second local oscillator light. The wavelength λ1 of the first local oscillator light is not equal to the wavelength λs of the signal light, and the wavelength λ2 of the second local oscillator light is not equal to the wavelength λs of the signal light, and the following condition is satisfied: |λ1 - λs| ≠ |λ2 - λs|.

8. The method according to claim 7, characterized in that the method further includes: extracting a first intermediate frequency signal and a second intermediate frequency signal with different frequencies from the electrical signal; wherein, the first intermediate frequency signal is obtained by performing photoelectric conversion on the optical signal after coherent coupling of the first local oscillator light and the signal light, and the second intermediate frequency signal is obtained by performing photoelectric conversion on the optical signal after coherent coupling of the second local oscillator light and the signal light; performing filtering processing on the first intermediate frequency signal and the second intermediate frequency signal respectively to obtain a first signal and a second signal; wherein, the first signal carries first polarization direction information, and the second signal carries second polarization direction information; the first polarization direction and the second polarization direction are orthogonal to each other; performing digital signal processing on the first signal and the second signal to obtain received information.

Images