Optical transmission method and device

Abstract

The present application provides an optical transmission method and device, which relates to the field of communications and can reduce or even eliminate phase noise. Among them, the first optical transmission device includes a first circulator and a first receiving module. The first receiving module is connected to the first circulator. The first circulator is used to receive a second unmodulated optical signal from a second optical transmission device. The first receiving module is used to receive a second modulated optical signal from the second optical transmission device, and to receive a second unmodulated optical signal from the first circulator. Among them, the second modulated optical signal is obtained by modulating the first unmodulated optical signal, and the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal. The first unmodulated optical signal and the second unmodulated optical signal are separated by a third unmodulated optical signal, and the third unmodulated optical signal is an optical signal provided by the first optical transmission device to the second optical transmission device.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of communications, and in particular, to an optical transmission method and device. Background Art

[0002] In a communication system, a first optical transmission device provides a third unmodulated optical signal to a second optical transmission device, so that the second optical transmission device performs modulation based on the third unmodulated optical signal to obtain a second modulated optical signal. Then, the first optical transmission device receives the second modulated optical signal from the second optical transmission device, and uses local oscillator light to perform coherent detection on the second modulated optical signal. The local oscillator light and the third unmodulated optical signal are obtained by separating the same optical signal on the first optical transmission device side.

[0003] However, the above communication system has large phase noise. Summary of the invention

[0004] The present application provides an optical transmission method and device, which can reduce or even eliminate phase noise.

[0005] In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

[0006] In a first aspect, an embodiment of the present application provides a first optical transmission device, which includes a first circulator and a first receiving module. The first receiving module is connected to the first circulator. The first circulator is used to receive a second unmodulated optical signal from a second optical transmission device. The first receiving module is used to receive a second modulated optical signal from the second optical transmission device, and to receive a second unmodulated optical signal from the first circulator. The second modulated optical signal is obtained by modulating the first unmodulated optical signal, and the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal. The first unmodulated optical signal and the second unmodulated optical signal are separated by a third unmodulated optical signal, and the third unmodulated optical signal is an optical signal provided by the first optical transmission device to the second optical transmission device.

[0007] In this way, the transmission paths of the second modulated optical signal and the second unmodulated optical signal are the same or close. The second modulated optical signal is obtained by modulating the first unmodulated optical signal, and the first unmodulated optical signal and the second unmodulated optical signal are obtained by separating the same optical signal provided by the first optical transmission device, that is, the third unmodulated optical signal. Moreover, the transmission paths of the second modulated optical signal and the second unmodulated optical signal are the same or close, so there is no frequency difference between the two, and they are coherent light, thereby reducing or even eliminating phase noise.

[0008] In one possible design, the first circulator is further connected to the second circulator. The second optical transmission device includes the second circulator. The first circulator is used to receive the second unmodulated optical signal from the second optical transmission device, including: receiving the second unmodulated optical signal from the second circulator, thereby achieving reception of the second unmodulated optical signal.

[0009] In a possible design, the first optical transmission device of the embodiment of the present application further includes a first polarization control module. The first polarization control module is connected to the first circulator. The first polarization control module is used to control the polarization of the second unmodulated optical signal.

[0010] During the transmission of the second unmodulated optical signal, the polarization state of the second unmodulated optical signal will randomly rotate, which will cause the coherent detection to fail. The first polarization control module can convert the polarization state of the second unmodulated optical signal to the desired polarization state, which is conducive to the normal coherent detection.

[0011] In one possible design, the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal, including: the second unmodulated optical signal after polarization control is used to perform coherent detection on the second modulated optical signal.

[0012] In this way, the local oscillator light used for coherent detection is the second unmodulated optical signal after polarization control. Since the second unmodulated optical signal has higher energy in the desired polarization state, the influence of random polarization state changes is eliminated or reduced, so the accuracy of coherent detection is improved.

[0013] In a possible design, the first polarization control module is further used to control the polarization of the first modulated optical signal, wherein the first modulated optical signal is an optical signal sent by the first optical transmission device to the second optical transmission device.

[0014] In this way, when the polarization control of the third unmodulated optical signal is also performed on the second optical transmission device side, the polarization state of the local oscillator light for coherent detection performed by the second optical transmission device is the same as that of the first modulated optical signal. After the coherent detection, an electrical signal can be obtained, and the target information can be obtained based on the electrical signal. There is no need to perform polarization demultiplexing processing, which reduces the system power consumption. There is no need to independently design a chip for performing polarization demultiplexing, which helps to reduce system costs.

[0015] In a possible design, the first optical transmission device of the embodiment of the present application further includes a first transmitting module. The first transmitting module is connected to the first circulator, and is used to send a first modulated optical signal to the first polarization control module through the first circulator, so that the first optical transmission device can provide the first optical modulated signal to the second optical transmission device.

[0016] In one possible design, the first optical transmission device is an optical transmission device on the active antenna processing unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side. Alternatively, the first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

[0017] In a second aspect, an embodiment of the present application provides a second optical transmission device, which includes a second coupler, a second transmitting module and a second circulator. The second transmitting module is connected to the second coupler and the second circulator respectively. The second coupler is used to separate the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal. The third unmodulated optical signal is an optical signal provided by the first optical transmission device. The second transmitting module is used to send a second modulated optical signal to the first optical transmission device. The second modulated optical signal is obtained by modulating the first unmodulated optical signal. The second circulator is used to receive the second unmodulated optical signal from the second coupler, and to send the second unmodulated optical signal to the first optical transmission device. The second unmodulated optical signal is used for coherent detection of the second modulated optical signal.

[0018] In one possible design, the second circulator is further connected to the first circulator. The first optical transmission device includes the first circulator. The second circulator is used to send the second unmodulated optical signal to the first optical transmission device, including: sending the second unmodulated optical signal to the first circulator, thereby achieving the sending of the second unmodulated optical signal.

[0019] In a possible design, the second optical transmission device of the embodiment of the present application further includes a second polarization control module, wherein the second polarization control module is connected to the second coupler and is used to control the polarization of the third unmodulated optical signal.

[0020] During the transmission of the third unmodulated optical signal, the polarization state of the third unmodulated optical signal will randomly rotate, which will cause the coherent detection to fail. The second polarization control module can convert the polarization state of the third unmodulated optical signal to the desired polarization state, which is conducive to the normal coherent detection.

[0021] In one possible design, the second coupler is used to separate the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal, including: separating the third unmodulated optical signal after polarization control into at least a first unmodulated optical signal and a second unmodulated optical signal.

[0022] That is to say, the first unmodulated optical signal and the second unmodulated optical signal are also polarization-controlled optical signals.

[0023] In a possible design, the second coupler is further used to separate the third unmodulated optical signal after polarization control into a fifth unmodulated optical signal. The fifth unmodulated optical signal is used for coherent detection of the first modulated optical signal, and the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

[0024] In this way, the local oscillator light used for coherent detection is the fifth unmodulated optical signal after polarization control. Since the fifth unmodulated optical signal has higher energy in the desired polarization state, the influence of random polarization state changes is eliminated or reduced, so the accuracy of coherent detection is improved.

[0025] In a possible design, the second optical transmission device of the embodiment of the present application further includes a second receiving module. The second receiving module is connected to the second circulator and the second coupler respectively, and is used to receive the first modulated optical signal from the first optical transmission device through the second circulator, and receive the fifth unmodulated optical signal from the second coupler, thereby realizing coherent detection of the first modulated optical signal.

[0026] In a possible design, the second polarization control module is also connected to the second transmitting module and is used to control the polarization of the second modulated optical signal.

[0027] In this way, when the polarization control of the second unmodulated optical signal is also performed on the first optical transmission device side, the local oscillator light (i.e., the above-mentioned second unmodulated optical signal) used for coherent detection by the first optical transmission device has the same polarization state as the second modulated optical signal. After coherent detection, an electrical signal can be obtained, and target information can be obtained based on the electrical signal. There is no need to perform polarization demultiplexing processing, which reduces system power consumption. There is no need to independently design a chip for performing polarization demultiplexing, which helps to reduce system costs.

[0028] In a possible design, the second optical transmission device of the embodiment of the present application further includes a third circulator. The second polarization control module is connected to the second coupler, including: the second polarization control module is connected to the second coupler through the third circulator, thereby realizing unidirectional transmission of the third unmodulated optical signal. The second polarization control module is also connected to the second transmitting module, including: the second polarization control module is also connected to the second transmitting module through the third circulator, thereby realizing unidirectional transmission of the second modulated optical signal.

[0029] In one possible design, the first optical transmission device is an optical transmission device on the active antenna processing unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side. Alternatively, the first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

[0030] In a third aspect, an embodiment of the present application provides an optical transmission method, which is applied to a first optical transmission device. The device includes a first circulator and a first receiving module. The first circulator is connected to the first receiving module. The method includes: the first circulator receives a second unmodulated optical signal from a second optical transmission device. The first receiving module receives a second modulated optical signal from the second optical transmission device, and receives a second unmodulated optical signal from the first circulator. The second modulated optical signal is obtained by modulating the first unmodulated optical signal, and the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal. The first unmodulated optical signal and the second unmodulated optical signal are separated by a third unmodulated optical signal, and the third unmodulated optical signal is an optical signal provided by the first optical transmission device to the second optical transmission device.

[0031] In a possible design, the first circulator receives the second unmodulated optical signal from the second optical transmission device, including: the first circulator receives the second unmodulated optical signal from the second circulator. The first circulator is also connected to the second circulator, and the second optical transmission device includes the second circulator.

[0032] In a possible design, the optical transmission method of the embodiment of the present application further includes: a first polarization control module controls the polarization of the second unmodulated optical signal. The first optical transmission device further includes a first polarization control module, and the first polarization control module is connected to the first circulator.

[0033] In one possible design, the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal, including: the second unmodulated optical signal after polarization control is used to perform coherent detection on the second modulated optical signal.

[0034] In a possible design, the optical transmission method of the embodiment of the present application further includes: a first polarization control module controls the polarization of a first modulated optical signal, wherein the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

[0035] In a possible design, the optical transmission method of the embodiment of the present application further includes: the first transmitting module sends a first modulated optical signal to the first polarization control module through the first circulator. The first optical transmission device further includes a first transmitting module, and the first transmitting module is connected to the first circulator.

[0036] In one possible design, the first optical transmission device is an optical transmission device on the active antenna processing unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side. Alternatively, the first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

[0037] In a fourth aspect, an embodiment of the present application provides an optical transmission method, which is applied to a second optical transmission device. The device includes a second coupler, a second transmitting module, and a second circulator. The method includes: the second coupler separates the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal. The third unmodulated optical signal is an optical signal provided by the first optical transmission device. The second transmitting module sends a second modulated optical signal to the first optical transmission device. The second modulated optical signal is obtained by modulating the first unmodulated optical signal. The second circulator receives the second unmodulated optical signal from the second coupler, and sends the second unmodulated optical signal to the first optical transmission device. The second unmodulated optical signal is used for coherent detection of the second modulated optical signal.

[0038] In a possible design, the second circulator sends the second unmodulated optical signal to the first optical transmission device, including: the second circulator sends the second unmodulated optical signal to the first circulator. The second circulator is also connected to the first circulator, and the first optical transmission device includes the first circulator.

[0039] In a possible design, the optical transmission method of the embodiment of the present application further includes: a second polarization control module controls the polarization of the third unmodulated optical signal. The second optical transmission device further includes a second polarization control module, and the second polarization control module is connected to the second coupler.

[0040] In one possible design, the second coupler separates the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal, including: the second coupler separates the third unmodulated optical signal after polarization control into at least a first unmodulated optical signal and a second unmodulated optical signal.

[0041] In a possible design, the optical transmission method of the embodiment of the present application further includes: the second coupler separates the third unmodulated optical signal after polarization control into a fifth unmodulated optical signal. The fifth unmodulated optical signal is used for coherent detection of the first modulated optical signal, and the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

[0042] In a possible design, the optical transmission method of the embodiment of the present application further includes: the second receiving module receives the first modulated optical signal from the first optical transmission device through the second circulator, and receives the fifth unmodulated optical signal from the second coupler. The device also includes a second receiving module, and the second receiving module is connected to the second circulator and the second coupler respectively.

[0043] In a possible design, the optical transmission method of the embodiment of the present application further includes: a second polarization control module controls the polarization of the second modulated optical signal, wherein the second polarization control module is also connected to the second transmitting module.

[0044] In one possible design, the first optical transmission device is an optical transmission device on the active antenna processing unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side. Alternatively, the first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

[0045] In a fifth aspect, an embodiment of the present application provides a computer-readable storage medium, in which a program is stored. When the program is called by a processor, the method of the third aspect or any one of the third aspects is executed, or the method of the fourth aspect or any one of the fourth aspects is executed.

[0046] In a sixth aspect, an embodiment of the present application provides a computer program product comprising instructions. When the computer program product is called by a processor, the method of the third aspect or any one of the third aspects is executed, or the method of the fourth aspect or any one of the fourth aspects is executed.

[0047] In a seventh aspect, an embodiment of the present application provides a communication system, the system comprising the first optical transmission device in the first aspect or any item in the first aspect, and the second optical transmission device in the second aspect or any item in the second aspect.

[0048] Among them, the technical effects brought about by any design in the second to seventh aspects can refer to the beneficial effects in the corresponding methods provided above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A communication system architecture diagram provided for an embodiment of the present application;

[0050] Figure 2a A diagram of another communication system architecture provided in an embodiment of the present application;

[0051] Figure 2b A diagram of another communication system architecture provided in an embodiment of the present application;

[0052] Figure 3a A diagram of another communication system architecture provided in an embodiment of the present application;

[0053] Figure 3b A diagram of another communication system architecture provided in an embodiment of the present application;

[0054] Figure 4 A diagram of another communication system architecture provided in an embodiment of the present application;

[0055] Figure 5 A schematic diagram of a process of an optical transmission method provided in an embodiment of the present application;

[0056] Figure 6A schematic diagram of a flow chart of another optical transmission method provided in an embodiment of the present application;

[0057] Figure 7 A schematic diagram of a flow chart of another optical transmission method provided in an embodiment of the present application;

[0058] Figure 8 A schematic diagram of a flow chart of another optical transmission method provided in an embodiment of the present application;

[0059] Fig. 9 A schematic diagram of a flow chart of another optical transmission method provided in an embodiment of the present application;

[0060] Fig.10 A schematic flow chart of another optical transmission method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0061] The terms "first" and "second" in the specification and drawings of the present application are used to distinguish different objects, or to distinguish different treatments of the same object, rather than to describe the specific order of objects. In addition, the terms "including" and "having" mentioned in the description of the present application and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes other steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices. In the embodiment of the present application, "multiple" includes two or more. In the embodiment of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiment of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or design schemes. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way. In the embodiment of the present application, "transmission" includes "sending" or "receiving".

[0062] First, in order to facilitate understanding of the embodiments of the present application, the relevant technologies involved in the present application are briefly introduced below.

[0063] 1. Optical modulation, unmodulated optical signal, modulated optical signal

[0064] Optical modulation generally refers to the process of changing the parameters of an optical carrier so that the optical carrier carries information. Exemplarily, the parameters of the optical carrier include amplitude, intensity, phase, or frequency.

[0065] In the embodiment of the present application, an optical carrier that has not been optically modulated is described as an unmodulated optical signal, such as laser light emitted by a laser, or light provided by other light sources, etc., and the embodiment of the present application is not limited to this.

[0066] In the embodiment of the present application, an optical signal that has undergone optical modulation is described as a modulated optical signal, such as an optical signal that has undergone amplitude modulation, intensity modulation, phase modulation, or frequency modulation.

[0067] 2. Phase noise

[0068] Phase noise generally causes the signal to have a random phase shift in the time domain, and this phase shift can also be observed in the frequency domain.

[0069] 3. Coherent optical transmission technology

[0070] It mainly adopts a single-frequency coherent light source and uses multiple dimensional parameters of light such as phase, frequency, amplitude, etc. to carry more modulation information, so as to make full use of the optical fiber bandwidth and achieve ultra-high capacity transmission.

[0071] By way of example, a system for communicating using coherent optical transmission technology is described below. Figure 1 1 is a schematic diagram of the architecture of a conventional communication system 1000 provided in an embodiment of the present application. Figure 1 As shown, the communication system 1000 includes a first optical transmission device 110 and a second optical transmission device 120 .

[0072] The first optical transmission device 110 includes a laser 111, a coupler 112, a transmitting module 113, a circulator 114, a receiving module 115 and a digital signal processing (DSP) module 116. In the first optical transmission device 110, the laser 111 is connected to the coupler 112, and the coupler 112 is also connected to the transmitting module 113, a port of the circulator 114 and the receiving module 115 respectively. The transmitting module 113 is also connected to the optical interface 1. Another port of the circulator 114 is connected to the optical interface 2. Another port of the circulator 114 is connected to the receiving module 115. The receiving module 115 is also connected to the DSP module 116.

[0073] The second optical transmission device 120 includes a receiving module 121, a DSP module 122, a coupler 123, a circulator 124, and a transmitting module 125. In the second optical transmission device 120, the receiving module 121 is connected to the optical interface 3, and the receiving module 121 is also connected to the DSP module 122 and the coupler 123 respectively. The coupler 123 is also connected to one port of the circulator 124 and the transmitting module 125 respectively, another port of the circulator 124 is connected to the transmitting module 125, and another port of the circulator 124 is connected to the optical interface 4.

[0074] The optical interface 1 is connected to the optical interface 3 via a single-mode optical fiber 130 , and the optical interface 2 is connected to the optical interface 4 via a single-mode optical fiber 140 .

[0075] Exemplarily, the processing process of each component in the first optical transmission device 110 is as follows:

[0076] The laser 111 emits an unmodulated optical signal 1. After receiving the unmodulated optical signal 1 from the laser 111, the coupler 112 separates the received unmodulated optical signal 1 into one of the following combinations:

[0077] The first item, unmodulated optical signal 2, unmodulated optical signal 3 and unmodulated optical signal 4;

[0078] The second item, unmodulated optical signal 2 and unmodulated optical signal 3;

[0079] The third item, unmodulated optical signal 3 and unmodulated optical signal 4.

[0080] When the unmodulated optical signal 2 is separated, the coupler 112 sends the unmodulated optical signal 2 to the transmitting module 113 as the local oscillator light of the transmitting module 113. The transmitting module 113 modulates the unmodulated optical signal 2 using the information 1 to obtain a first modulated optical signal, and sends the first modulated optical signal to the second optical transmission device 120 through the optical interface 1 and the single-mode optical fiber 130.

[0081] When the unmodulated optical signal 3 is separated, the coupler 112 sends the unmodulated optical signal 3 to one port of the circulator 114. The circulator 114 sends the unmodulated optical signal 3 to the optical interface 2 through another port, so as to send the unmodulated optical signal 3 to the second optical transmission device 120 through the single mode optical fiber 140.

[0082] When the unmodulated optical signal 4 is separated, the coupler 112 sends the unmodulated optical signal 4 to the receiving module 115 as the local oscillator light of the receiving module 115. Figure 1 As shown by the dotted arrow in FIG. 1 . The circulator 114 also receives the second modulated optical signal from the optical interface 2 and sends the second modulated optical signal to the receiving module 115. Figure 1 The receiving module 115 uses the unmodulated optical signal 4 to perform coherent detection on the second modulated optical signal to obtain the electrical signal 2, and sends the electrical signal 2 to the DSP module 116. The DSP module 116 samples, performs analog-to-digital conversion and digital signal processing on the electrical signal 2 to obtain information 2.

[0083] The processing process of each component in the second optical transmission device 120 is as follows:

[0084] When the first optical transmission device 110 sends the unmodulated optical signal 3 to the second optical transmission device 120 through the single-mode optical fiber 140, the circulator 124 receives the unmodulated optical signal 3 through the optical interface 4 and sends the unmodulated optical signal 3 to the coupler 123. The coupler 123 separates the unmodulated optical signal 3 into one of the following combinations:

[0085] The first item, unmodulated optical signal 5 and unmodulated optical signal 6.

[0086] The second item is the unmodulated optical signal 5. That is, the unmodulated optical signal 3 is used as the unmodulated optical signal 5.

[0087] The third item is the unmodulated optical signal 6. That is to say, the unmodulated optical signal 3 is used as the unmodulated optical signal 6.

[0088] When the unmodulated optical signal 5 is separated, the coupler 123 sends the unmodulated optical signal 5 to the receiving module 121 as the local oscillator light of the receiving module 121. When the first optical transmission device 110 sends the first modulated optical signal to the second optical transmission device 120 through the single-mode optical fiber 130, the receiving module 121 receives the first modulated optical signal through the optical interface 3. The receiving module 115 uses the unmodulated optical signal 5 to perform coherent detection on the first modulated optical signal to obtain the electrical signal 1, and sends the electrical signal 1 to the DSP module 116. The DSP module 116 samples, performs analog-to-digital conversion, and performs digital signal processing on the electrical signal 1 to obtain information 1.

[0089] When the unmodulated optical signal 6 is separated, the coupler 123 sends the unmodulated optical signal 6 to the transmitting module 125 as the local oscillator light of the transmitting module 125. The transmitting module 125 modulates the unmodulated optical signal 6 using the information 2 to obtain a second modulated optical signal, and sends the second modulated optical signal to the circulator 124. The circulator 124 sends the second modulated optical signal to the first optical transmission device 110 through the optical interface 4 and the single-mode optical fiber 140. Figure 1 As shown by the solid arrow in .

[0090] It should be understood that Figure 1 This is merely an exemplary description of the architecture and working process of a traditional communication system as a possible implementation method and should not be construed as a limitation on the embodiments of the present application.

[0091] In summary, when the second optical transmission device 120 sends the second modulated optical signal to the first optical transmission device 110 through the single-mode optical fiber 140, for the second modulated optical signal, the optical signal used for coherent detection is the unmodulated optical signal 4. However, when the distance between the first optical transmission device 110 and the second optical transmission device 120 is far, the difference in transmission path length between the unmodulated optical signal 4 and the second modulated optical signal is large, and the two are incoherent, resulting in large phase noise.

[0092] In view of this, an embodiment of the present application provides a communication system. Figure 2a As shown, in the communication system 2000 provided in the embodiment of the present application, a first optical transmission device 210 and a second optical transmission device 220 are included. Exemplarily, the first optical transmission device 210 and the second optical transmission device 220 are connected through optical fibers, such as the optical interface 1 of the first optical transmission device 210 is connected to the optical interface 3 of the second optical transmission device 220 through the single-mode optical fiber 230, and the optical interface 2 of the first optical transmission device 210 is connected to the optical interface 4 of the second optical transmission device 220 through the single-mode optical fiber 240.

[0093] Exemplarily, the first optical transmission device 210 can be implemented as an optical transmission device on the side of the baseband unit (BBU), such as an optical module pluggable on the BBU, and the second optical transmission device 220 can be implemented as an optical transmission device on the side of the active antenna unit (AAU), such as an optical module pluggable on the AAU. Or, conversely, the first optical transmission device 210 can be implemented as an optical transmission device on the AAU side, such as an optical module pluggable on the AAU, and the second optical transmission device 220 can be implemented as an optical transmission device on the side of the BBU, such as an optical module pluggable on the BBU. It should be understood that with the evolution of technology, AAU and BBU may have other names, or other devices that can realize the functions of AAU and BBU, and the embodiments of the present application do not limit the names of AAU and BBU. Similarly, the first optical transmission device 210 and the second optical transmission device 220 may also have other names, or be implemented as optical transmission devices on the side of other devices, and the embodiments of the present application do not limit this.

[0094] Among them, there may be two signal transmission directions between the first optical transmission device 210 and the second optical transmission device 220, namely: the first optical transmission device 210 transmits to the second optical transmission device 220, which may be referred to as the first transmission direction; and the second optical transmission device 220 transmits to the first optical transmission device 210, which may be referred to as the second transmission direction. Exemplarily, in the case of being implemented as an AAU and a BBU, the process of the BBU sending a modulated optical signal to the AAU may also be referred to as downlink transmission. The process of the AAU sending a modulated optical signal to the BBU may also be referred to as uplink transmission. In an embodiment of the present application, for the modulated optical signal, the modulated optical signal transmitted in the first transmission direction is described as the first modulated optical signal. The modulated optical signal transmitted in the second transmission direction is described as the second modulated optical signal.

[0095] like Figure 2a As shown, in the first optical transmission device 210, the first optical transmission device 210 includes a first circulator 214 and a first receiving module 216. Figure 2aAs shown in the solid line box in . The first circulator 214 is connected to the first receiving module 216. Exemplarily, one port of the first circulator 214 is connected to the first receiving module 216 via a polarization-maintaining optical fiber or an optical waveguide.

[0096] Among them, the first circulator 214 can realize unidirectional transmission of signals. Exemplarily, the first circulator 214 can be a three-port device. For example, the three ports of the first circulator 214 are respectively recorded as port A, port B and port C. For the first circulator 214, the signal received by port A is sent through port B, the signal received by port B is sent through port C, and the signal received by port C is sent through port A, thereby realizing unidirectional transmission of signals. It should be understood that in the embodiment of the present application, the three-port device is only an exemplary description of the first circulator 214. Of course, the first circulator 214 can also have other numbers of ports, as long as it can realize unidirectional transmission of signals. The embodiment of the present application does not limit the specific implementation of the first circulator 214.

[0097] In the embodiment of the present application, the first circulator 214 is used to receive the unmodulated optical signal 7 from the second optical transmission device 220. Figure 2a For example, the first circulator 214 is used to receive the unmodulated optical signal 7 from the second optical transmission device 220 through the optical interface 1 and the single-mode optical fiber 230 .

[0098] Optionally, in the case where the second optical transmission device 220 includes a second circulator 221, Figure 2a For example, the first circulator 214 is connected to the second circulator 221, such as the first circulator 214 is connected to the second circulator 221 through the optical interface 1, the single-mode optical fiber 230, and the optical interface 3. The first circulator 214 is used to receive the unmodulated optical signal 7 from the second circulator 221 through the optical interface 1, the single-mode optical fiber 230 and the optical interface 3. Figure 2a As shown by the dotted arrow in the figure. The second circulator 221 can refer to the introduction of the second optical transmission device 220, which will not be repeated here.

[0099] Among them, the first receiving module 216 can convert the optical signal into an electrical signal. The first receiving module 216 can also be called a receiver, or a coherent receiver. In the embodiment of the present application, only the receiving module is used as an example for introduction. Exemplarily, the first receiving module 216 can be implemented as an integrated coherent receiver (ICR). Coherence means that the first receiving module 216 can restore amplitude information and phase information.

[0100] In the embodiment of the present application, the first receiving module 216 is used to receive the second modulated optical signal from the second optical transmission device 220. Figure 2a For example, the first receiving module 216 is used to receive the second modulated optical signal from the second optical transmission device 220 through the optical interface 2 and the single-mode optical fiber 240 .

[0101] Optionally, in the case where the first optical transmission device 210 includes the fourth circulator 215 and the second optical transmission device 220 includes the third circulator 225, as shown in FIG. Figure 2a As shown, the first receiving module 216 is connected to the fourth circulator 215, and the fourth circulator 215 is connected to the third circulator 225 through the optical interface 2, the single-mode optical fiber 240 and the optical interface 4. The first receiving module 216 is used to receive the second modulated optical signal from the third circulator 225 through the fourth circulator 215, the optical interface 2 and the single-mode optical fiber 240. Figure 2a The first receiving module 216 is also used to receive the unmodulated optical signal 7 from the first circulator 214. The unmodulated optical signal 7 is used to perform coherent detection on the second modulated optical signal to obtain the electrical signal 2.

[0102] The second modulated optical signal is obtained by modulating the unmodulated optical signal 6, and the details can be found in the introduction of the second transmitting module 226. The unmodulated optical signal 6 and the unmodulated optical signal 7 are obtained by separating the unmodulated optical signal 3, and the details can be found in the description of the second coupler 224.

[0103] The unmodulated optical signal 3 is an optical signal provided by the first optical transmission device 210 to the second optical transmission device 220. Figure 2a As shown by the thin solid arrow in .

[0104] Optional, still with Figure 2a For example, in the first optical transmission device 210, a laser 211, a first coupler 212 and a fourth circulator 215 are included. Figure 2a As shown in the dotted box in . The first coupler 212 is connected to the laser 211 and the fourth circulator 215 respectively. For example, the first coupler 212 is connected to the laser 211 through a polarization-maintaining fiber or an optical waveguide, and the first coupler 212 is connected to the fourth circulator 215 through a polarization-maintaining fiber or an optical waveguide.

[0105] Exemplarily, the laser 211 can provide a continuous wave with a wavelength of λ. The wavelength λ can be in the 0 band from about 1260 nanometers (nm) to about 1360 nm, or in the C / L band from about 1530 nm to about 1625 nm. The laser 211 can be a distributed feedback (DFB) laser without temperature control or other wavelength control. In this case, the laser 211 can be called an uncooled laser and can have a line width greater than 100 kilohertz (kHz) or even up to 1 megahertz (MHz) or more. Alternatively, the laser 211 is a narrow line width external cavity laser (ECL).

[0106] In the embodiment of the present application, the laser 211 is used to emit an unmodulated optical signal 1. The unmodulated optical signal 1 is used for modulation or coherent detection of an optical signal. It should be understood that the embodiment of the present application only takes the laser providing the unmodulated optical signal 1 as an example for introduction. Of course, other devices may also provide light sources, and the embodiment of the present application does not limit this.

[0107] Exemplarily, the first coupler 212 can separate the input optical signal to obtain at least one optical signal. For example, the first coupler 212 evenly separates the input optical signal into two optical signals. It should be understood that the embodiment of the present application does not limit the number of separated light beams and the separation ratio. The coupler may also be called a splitter or a splitter. In the embodiment of the present application, only the coupler is used as an example for introduction.

[0108] In the embodiment of the present application, the first coupler 212 is used to receive the unmodulated optical signal 1 from the laser 211, and to separate the unmodulated optical signal 1. The separation result includes one of the following:

[0109] The first item is unmodulated optical signal 2 and unmodulated optical signal 3. The first coupler 212 is used to separate the unmodulated optical signal 1 into the unmodulated optical signal 2 and the unmodulated optical signal 3 according to a certain ratio. The ratio used by the first coupler 212 for separation can be a preset value or a value determined based on a reference factor. Exemplarily, the reference factor includes: the transmission distance between the first optical transmission device 210 and the second optical transmission device 220.

[0110] The second item is the unmodulated optical signal 3. That is, the unmodulated optical signal 1 is not separated and is directly used as the unmodulated optical signal 3.

[0111] According to the above separation result, when the unmodulated optical signal 2 is separated, the unmodulated optical signal 2 is used to modulate the first modulated optical signal to realize the transmission of the modulated optical signal in the first transmission direction. For details, see Figure 1Or the introduction of the first transmitting module 213 will not be repeated here.

[0112] According to the above separation result, when the unmodulated optical signal 3 is separated, the unmodulated optical signal 3 is used for modulation and coherent detection of the second modulated optical signal. For details, see the introduction of the second transmitting module 226 and the first receiving module 216.

[0113] It should be noted that compared with Figure 1 In terms of the coupler 112, Figure 2a The first coupler 212 in the embodiment does not directly provide the local oscillator light to the first receiving module 216, that is, the optical signal 4 is not modulated.

[0114] Exemplarily, the fourth circulator 215 can realize unidirectional transmission of signals. For example, the fourth circulator 215 can also be a three-port device, and the details are as described in the first circulator 214, which will not be described here.

[0115] In the embodiment of the present application, the fourth circulator 215 is used to receive the unmodulated optical signal 3 from the first coupler 212, and send the unmodulated optical signal 3 to the second optical transmission device 220. Figure 2a For example, one port of the fourth circulator 215 is used to receive the unmodulated optical signal 3 from the first coupler 212. Another port of the fourth circulator 215 is used to send the unmodulated optical signal 3 to the third circulator 225 through the optical interface 2, the single-mode optical fiber 240 and the optical interface 4.

[0116] It can be seen from this that when the first optical transmission device 210 includes the above-mentioned laser 211, the first coupler 212 and the fourth circulator 215, the above-mentioned three devices work together to achieve the separation and transmission of the unmodulated optical signal 3, so that the first optical transmission device 210 provides the unmodulated optical signal 3 to the second optical transmission device 220.

[0117] It should be understood that Figure 2a In the embodiment, only the connection relationship between the laser 211, the first coupler 212 and the fourth circulator 215 is taken as an example to introduce the generation and transmission of the unmodulated optical signal 3. Of course, the first optical transmission device may also have other devices, or connection relationships between devices, to achieve the generation and transmission functions of the unmodulated optical signal 3, and the embodiment of the present application is not limited to this.

[0118] Optionally, the first optical transmission device 210 further includes a first DSP module 217, such as Figure 2aAs shown in the dotted box in FIG. 2 . The first DSP module 217 is connected to the first receiving module 216. Exemplarily, the first DSP module 217 is connected to the first receiving module 216 via an electrical connection line. The first DSP module 217 is used to receive the electrical signal 2 from the first receiving module 216, and determine the information 2 based on the electrical signal 2. For details, see Figure 1 The introduction of will not be repeated here.

[0119] It should be noted that compared with Figure 1 As for the receiving module 115, Figure 2a The local oscillator light of the first receiving module 216 is provided by the first circulator 214, that is, the unmodulated optical signal 7. The unmodulated optical signal 7 is obtained after the unmodulated optical signal 3 is separated by the second coupler 224, and the unmodulated optical signal 3 is the optical signal separated by the first coupler 212. In other words, the local oscillator light of the first receiving module 216 is not the optical signal directly separated by the first coupler 212, but the optical signal separated by the first coupler 212, and then fed back to the first optical transmission device 210 after passing through the second optical transmission device 220.

[0120] It should be understood that in the first optical transmission device 210, only the first DSP module 217 is taken as an example to introduce the device capable of processing the electrical signal 2. Of course, the first optical transmission device 210 may also have other devices, or connection relationships between devices, to realize the processing function of the electrical signal 2, and the embodiment of the present application is not limited to this.

[0121] For the first optical transmission device 210, the second modulated optical signal and the unmodulated optical signal 7 are both from the second optical transmission device 220, so the transmission paths of the second modulated optical signal and the unmodulated optical signal 7 are the same or close. Among them, the second modulated optical signal is obtained by modulating the unmodulated optical signal 6, and the unmodulated optical signal 6 and the unmodulated optical signal 7 are obtained by separating the same optical signal provided by the first optical transmission device 210, that is, the unmodulated optical signal 3 mentioned above. In addition, the transmission paths of the second modulated optical signal and the unmodulated optical signal 7 are the same or close, so there is no frequency difference between the two, and they are coherent light, thereby reducing or even eliminating phase noise.

[0122] like Figure 2a As shown, in the second optical transmission device 220, the second optical transmission device 220 includes a second coupler 224, a second circulator 221, and a second transmitting module 226. The second coupler 224 is connected to the second circulator 221 and the second transmitting module 226, respectively. Exemplarily, an output port of the second coupler 224 is connected to a port of the second circulator 221 through a polarization-maintaining fiber or an optical waveguide. Another output port of the second coupler 224 is connected to the second transmitting module 226 through a polarization-maintaining fiber or an optical waveguide.

[0123] The second coupler 224 can also separate the input optical signal. For example, the specific implementation of the second coupler 224 can refer to the introduction of the first coupler 212, which will not be repeated here.

[0124] In the embodiment of the present application, the second coupler 224 is used to separate the unmodulated optical signal 3. The ratio used by the second coupler 224 when performing separation can refer to the introduction of the first coupler 212, which will not be repeated here. It should be understood that the ratio used by the second coupler 224 when performing separation can be the same as or different from the ratio used by the first coupler 212 when performing separation, and the embodiment of the present application does not limit this.

[0125] Optionally, the second optical transmission device 220 further includes a third circulator 225, such as Figure 2a As shown in the dotted box in . Among them, the third circulator 225 can also realize unidirectional transmission of signals. Exemplarily, the third circulator 225 can also be a three-port device. The specific implementation can refer to the introduction of the first circulator 214, which will not be repeated here. Exemplarily, the connection relationship between the third circulator 225 and the second coupler 224 is as follows: the input port of the second coupler 224 is connected to a port of the third circulator 225 through a polarization-maintaining fiber or an optical waveguide, and another port of the third circulator 225 is connected to the optical interface 4 through a polarization-maintaining fiber or an optical waveguide. In an embodiment of the present application, the third circulator 225 is used to receive the unmodulated optical signal 3 from the fourth circulator 215 through the optical interface 4, the single-mode optical fiber 240 and the optical interface 2, and send the unmodulated optical signal 3 to the second coupler 224, so that the second coupler 224 receives the unmodulated optical signal 3.

[0126] Exemplarily, the separation result of the second coupler 224 includes one of the following combinations:

[0127] The first item, unmodulated optical signal 5, unmodulated optical signal 6 and unmodulated optical signal 7.

[0128] The second item is the unmodulated optical signal 5. That is, the unmodulated optical signal 3 is not separated and is directly used as the unmodulated optical signal 5.

[0129] The third item, unmodulated optical signal 6 and unmodulated optical signal 7.

[0130] In the case where the unmodulated optical signal 5 is separated and obtained, the unmodulated optical signal 5 is used for coherent detection of the first modulated optical signal. For details, see Figure 1 Or the introduction of the second receiving module 222 will not be repeated here.

[0131] When the unmodulated optical signal 6 is separated, the second coupler 224 is used to send the unmodulated optical signal 6 to the second transmitting module 226. The unmodulated optical signal 6 is used to modulate the second modulated optical signal. For details, please refer to the introduction of the second transmitting module 226, which will not be repeated here.

[0132] When the unmodulated optical signal 7 is separated, the second coupler 224 is used to send the unmodulated optical signal 7 to the second circulator 221. The unmodulated optical signal 7 is provided to the first optical transmission device 210 to achieve coherent detection of the second modulated optical signal. For details, please refer to the description of the first receiving module 216, which will not be repeated here. Figure 2a For example, the second circulator 221 is used to send the unmodulated optical signal 7 to the first circulator 214 through the optical interface 3, the single-mode optical fiber 230 and the optical interface 1. Figure 2a As shown by the dotted arrow in .

[0133] It should be noted that compared with Figure 1 For the coupler 123, Figure 2a The second coupler 224 can also separate the unmodulated optical signal 7, and for details, please refer to the introduction of the separation result of the second coupler 224.

[0134] Among them, the second transmitting module 226 can convert the electrical signal into an optical signal. The second transmitting module 226 can also be called a transmitter, or a modulator. In the embodiment of the present application, only the transmitting module is used as an example for introduction. Exemplarily, the second transmitting module 226 can be implemented as a polarization multiplexing in-phase and quadrature (IQ) modulator. For example, the second transmitting module 226 uses amplitude information and phase information to modulate the unmodulated optical signal, such as using high-order quadrature amplitude modulation (QAM) to generate a modulated optical signal of a certain wavelength based on the electrical signal. It should be understood that the second transmitting module 226 can also be modulated using any other suitable modulation format, which is not limited in the embodiment of the present application.

[0135] In the embodiment of the present application, the second transmitting module 226 is used to send a second modulated optical signal to the first optical transmission device 210. The second modulated optical signal is obtained by modulating the unmodulated optical signal 6. Figure 2a For example, the second transmitting module 226 is used to send the second modulated optical signal to the first optical transmission device 210 through the optical interface 4.

[0136] Optionally, in the case where the second optical transmission device 220 includes a third circulator 225, Figure 2aFor example, the output port of the second transmitting module 226 is connected to a port of the third circulator 225 through a polarization-maintaining fiber or an optical waveguide. The second transmitting module 226 is used to send the second modulated optical signal to the third circulator 225. The third circulator 225 is used to send the second modulated optical signal to the optical interface 4, so that the second modulated optical signal is transmitted to the first optical transmission device 210 through the single-mode optical fiber 240. Figure 2a Indicated by the thick solid arrow.

[0137] The second circulator 221 can realize unidirectional signal transmission. For example, the second circulator 221 can also be a three-port device. For specific implementation, please refer to the introduction of the first circulator 214, which will not be repeated here.

[0138] In the embodiment of the present application, the second circulator 221 is used to receive the unmodulated optical signal 7 from the second coupler 224 and send the unmodulated optical signal 7 to the first optical transmission device 210. For example, Figure 2a As shown, the second circulator 221 is used to send the unmodulated optical signal 7 to the first optical transmission device 210 through the optical interface 3.

[0139] Optionally, in the case where the first optical transmission device 210 includes the first circulator 214, the second circulator 221 is connected to the first circulator 214. The second circulator 221 is used to send the unmodulated optical signal 7 to the first circulator 214, such as the second circulator 221 is used to send the unmodulated optical signal 7 to the first circulator 214 through the optical interface 3, the single-mode optical fiber 230 and the optical interface 1. Figure 2a As shown by the dotted arrow in . The unmodulated optical signal 7 is used for coherent detection of the second modulated optical signal. For details, please refer to the introduction of the first receiving module 216, which will not be repeated here.

[0140] For the second optical transmission device 220, the second modulated optical signal and the unmodulated optical signal 7 are transmitted to the first optical transmission device 210, so the transmission paths of the second modulated optical signal and the unmodulated optical signal 7 are the same or close. Among them, the second modulated optical signal is obtained by modulating the unmodulated optical signal 6, and the unmodulated optical signal 6 and the unmodulated optical signal 7 are obtained by separating the same optical signal provided by the first optical transmission device 210, that is, the unmodulated optical signal 3 mentioned above. In addition, the transmission paths of the second modulated optical signal and the unmodulated optical signal 7 are the same or close, so there is no frequency difference between the two, and they belong to coherent light, thereby reducing or even eliminating phase noise.

[0141] In the above, only the second modulated optical signal is taken as an example to introduce the connection relationship and function of each device from the aspects of modulation, transmission and demodulation. Optionally, the first modulated optical signal is taken as an example to introduce the connection relationship and function of each device from the aspects of modulation, transmission and coherent detection:

[0142] Optionally, the first optical transmission device 210 further includes a first transmitting module 213, such as Figure 2a As shown in the dotted box in . Among them, the first transmitting module 213 can also convert the electrical signal into an optical signal. For details, please refer to the introduction of the second transmitting module 226, which will not be repeated here. Exemplarily, the connection relationship between the first transmitting module 213 and other devices is as follows: the first transmitting module 213 is connected to the first coupler 212 and the first circulator 214 respectively. Exemplarily, the first transmitting module 213 is connected to the first coupler 212 through a polarization-maintaining fiber or an optical waveguide, and the first transmitting module 213 is connected to the first circulator 214 through a polarization-maintaining fiber or an optical waveguide.

[0143] In the embodiment of the present application, the functions of the first transmitting module 213 are described as follows:

[0144] In the case where the first coupler 212 separates and obtains the unmodulated optical signal 2, the first transmitting module 213 is used to receive the unmodulated optical signal 2 from the first coupler 212, modulate the unmodulated optical signal 2, and obtain a first modulated optical signal. For details, see Figure 1 The introduction of the first optical transmission device 210 will not be repeated here. It should be understood that in the embodiment of the present application, only the first transmitting module 213 is taken as an example to introduce the connection relationship between the first transmitting module 213 and other devices to achieve the generation function of the first modulated optical signal. Of course, the first optical transmission device 210 can also have other devices, or connection relationships between devices, to achieve the generation function of the first modulated optical signal, and the embodiment of the present application is not limited to this.

[0145] In addition, in the embodiment of the present application, the first circulator 214 is also used to receive the first modulated optical signal from the first transmitting module 213, and send the first modulated optical signal to the second optical transmission device 220. Exemplarily, the first circulator 214 is used to send the first modulated optical signal to the second circulator 221 through the optical interface 1, the single-mode optical fiber 230 and the optical receiving 3. Figure 2b As shown by the thick solid arrow in .

[0146] Optionally, in the second optical transmission device 220, the second circulator 221 is further configured to receive the first modulated optical signal from the first optical transmission device 210, and to send the first modulated optical signal to the second receiving module 222. Exemplarily, the second circulator 221 is configured to receive the first modulated optical signal from the first circulator 214 through the optical interface 3, and then send the first modulated optical signal to the second receiving module 222.

[0147] Optionally, the second optical transmission device 220 further includes a second receiving module 222, such as Figure 2aAs shown in the dotted box in . Among them, the second receiving module 222 can also convert the optical signal into an electrical signal. Exemplarily, the specific implementation of the second receiving module 222 can refer to the introduction of the first receiving module 216, which will not be repeated here. Exemplarily, the connection relationship between the second receiving module 222 and other devices is described as follows: the second receiving module 222 is connected to the second coupler 224 and the second circulator 221 respectively. Exemplarily, the second receiving module 222 is connected to the second coupler 224 through a polarization-maintaining fiber or an optical waveguide, and the second receiving module 222 is connected to the second circulator 221 through a polarization-maintaining fiber or an optical waveguide.

[0148] In the embodiment of the present application, the functions of the second receiving module 222 are described as follows:

[0149] The second receiving module 222 is used to receive the first modulated optical signal from the second circulator 221. In the case where the second coupler 224 separates the unmodulated optical signal 5, the unmodulated optical signal 5 is used to perform coherent detection on the first modulated optical signal. Exemplarily, the second receiving module 222 is also used to perform coherent detection on the first modulated optical signal using the unmodulated optical signal 5 to obtain the electrical signal 1. For details, see Figure 1 The introduction of will not be repeated here.

[0150] It should be understood that in the embodiment of the present application, only the second receiving module 222 is taken as an example to introduce the connection relationship between the second receiving module 222 and other devices to realize the receiving function of the second modulated optical signal. Of course, the second optical transmission device 220 can also have other devices, or connection relationships between devices, to realize the receiving function of the second modulated optical signal, and the embodiment of the present application is not limited to this.

[0151] Optionally, the second optical transmission device 220 further includes a second DSP module 223, such as Figure 2a As shown in the dotted box in FIG. The second DSP module 223 is connected to the second receiving module 222. Exemplarily, the second DSP module 223 is connected to the second receiving module 222 via an electrical connection line. The second DSP module 223 is used to receive the electrical signal 1 from the second receiving module 222, and determine the information 1 based on the electrical signal 1. For details, see Figure 1 The introduction of will not be repeated here.

[0152] It should be understood that in the second optical transmission device 220, only the second DSP module 223 is taken as an example to introduce the device capable of processing the electrical signal 1. Of course, the second optical transmission device 220 may also have other devices, or connection relationships between devices, to realize the processing function of the electrical signal 1, and the embodiment of the present application is not limited to this.

[0153] It can be seen that based on the connection relationship and functions of the above-mentioned various components, the modulation, transmission and coherent detection functions of the first modulated optical signal can be realized.

[0154] In some embodiments, Figure 3a As shown, the first optical transmission device 210 also includes a first polarization control (automatic polarization controller, APC) module 218, such as Figure 3a As shown in the thick solid box in . The polarization control module is a polarization state control device that can convert any dynamically changing input polarization state into any desired output polarization state. Exemplarily, the polarization control module uses the birefringence phenomenon of the crystal to change the polarization state, and obtains polarized light of the desired polarization state through a certain composition method and control algorithm. Among them, the composition method may include the number of wave plates connected in series and the relative azimuth relationship between each wave plate, and the control algorithm may include high-speed dynamic change of the azimuth angle of the wave plate and the relative phase difference of birefringence. Among them, the polarization control module can also be called a polarization controller. In the embodiments of the present application, only the polarization control module is taken as an example for introduction.

[0155] Exemplarily, the connection relationship between the first polarization control module 218 and other components is described as follows: the first polarization control module 218 is connected to the first circulator 214. Exemplarily, in combination with Figure 3a , the first polarization control module 218 is connected to the first circulator 214 through a polarization-maintaining fiber or an optical waveguide, and the first polarization control module 218 is connected to the optical interface 1 through a polarization-maintaining fiber or an optical waveguide. In addition, the first polarization control module 218 may also be arranged on the side of the second optical transmission device 220 instead of the first optical transmission device 210. For example, the second circulator 221 is connected to the optical interface 3 through the first polarization control module 218 ( Figure 3a (not shown), which is not limited in the embodiments of the present application.

[0156] It should be understood that the first polarization control module 218 and the first receiving module 216 may be independent devices, such as Figure 3a The first polarization control module 218 and the first receiving module 216 may also be provided together, such as the first polarization control module 218 is a component inside the first receiving module 216. Figure 3a Not shown.

[0157] The function of the first polarization control module 218 is described as follows: the first polarization control module 218 is used to control the polarization of the unmodulated optical signal 7. Exemplarily, the first polarization control module 218 is used to convert the polarization state of the unmodulated optical signal 7 to a desired polarization state after receiving the unmodulated optical signal 7 through the optical interface 1. The desired polarization state may be the same as the polarization state of the second modulated optical signal. The first polarization control module 218 is also used to send the polarization-controlled unmodulated optical signal 7 to the first receiving module 216 through the first circulator 214.

[0158] It should be understood that the optical interface 1 and the optical interface 3 are usually connected by a polarization-maintaining fiber to ensure that the unmodulated optical signal 7 has enough energy in a certain fixed polarization state as much as possible, so that the coherent detection can be carried out normally. However, in practical applications, the polarization-maintaining fiber is likely to be affected by squeezing or other changes in the application environment, such as trampling, construction stretching, etc., resulting in the degradation of its polarization state maintenance function. Then, the polarization state of the unmodulated optical signal 7 transmitted in the polarization-maintaining fiber will rotate randomly, which will cause the coherent detection to fail. The first polarization control module 218 can convert the polarization state of the unmodulated optical signal 7 to the desired polarization state, which is conducive to the normal coherent detection.

[0159] In this case, the unmodulated optical signal 7 is used to perform coherent detection on the second modulated optical signal, including: the unmodulated optical signal 7 after polarization control performs coherent detection on the second modulated optical signal. Figure 3a For example, when the second optical transmission device 220 sends an unmodulated optical signal 7 to the first optical transmission device 210, the first receiving module 216 is used to receive the unmodulated optical signal 7 after polarization control from the first circulator 214 as the local oscillator light to perform coherent detection on the second modulated optical signal.

[0160] In this way, the local oscillator light used for coherent detection is the unmodulated optical signal 7 after polarization control. Since the unmodulated optical signal 7 has higher energy in the desired polarization state, the influence of random polarization state changes is eliminated or reduced, so the accuracy of coherent detection is improved.

[0161] Optionally, the first polarization control module 218 is further used to control the polarization of the first modulated optical signal. The first modulated optical signal is an optical signal transmitted from the first optical transmission device 210 to the second optical transmission device 220. Figure 2b The introduction of Figure 3aFor example, the first circulator 214 is also used to send a first modulated optical signal to the first polarization control module 218. The first polarization control module 218 is used to control the polarization of the first modulated optical signal so that the first modulated optical signal after polarization control has more energy in the desired polarization direction. Among them, the first modulated optical signal after polarization control can have the same polarization state as the unmodulated optical signal 3 after polarization control. In the case where the unmodulated optical signal 3 is also polarized and controlled on the side of the second optical transmission device 220, the local oscillator light (i.e., the above-mentioned unmodulated optical signal 5) of the second receiving module 222 for coherent detection is the same as the polarization state of the first modulated optical signal. In this way, after the second receiving module 222 performs coherent detection, the electrical signal 1 can be obtained. The second DSP module 223 can obtain information 1 based on the electrical signal 1 without the need for polarization demultiplexing processing, which reduces system power consumption and does not require independent chip design, which helps to reduce system costs.

[0162] It should be understood that, when the coherent communication system 2000 includes the first polarization control module 218 , the single-mode optical fiber 230 may also be replaced by other connecting materials, such as ordinary optical fiber, to reduce system cost.

[0163] In some embodiments, the second optical transmission device 220 further includes a second polarization control module 227, such as Figure 3b As shown in the thick solid box in the figure. The polarization control module can refer to the introduction of the first polarization control module 218, which will not be repeated here.

[0164] Exemplarily, the connection relationship between the second polarization control module 227 and other components is described as follows:

[0165] The second polarization control module 227 is connected to the second coupler 224. Figure 3b , the second polarization control module 227 is connected to the second coupler 224 through the third circulator 225. In addition, the second polarization control module 227 may also be arranged on the first optical transmission device 210 side instead of the second optical transmission device 220 side. For example, the second fourth circulator 215 is connected to the optical interface 2 through the second polarization control module 227 ( Figure 3b (not shown), which is not limited in the embodiments of the present application.

[0166] It should be understood that the second polarization control module 227 and the second receiving module 222 can be independent devices, such as Figure 3b The second polarization control module 227 and the second receiving module 222 may also be provided together, for example, the second polarization control module 227 is a device inside the second receiving module 222, Figure 3b Not shown.

[0167] The functions of the second polarization control module 227 are as follows:

[0168] The second polarization control module 227 is used to control the polarization of the unmodulated optical signal 3. Exemplarily, the second polarization control module 227 is used to receive the unmodulated optical signal 3 through the optical interface 4, and convert the polarization state of the unmodulated optical signal 3 into a desired polarization state. The desired polarization state may be the same as the polarization state of the unmodulated optical signal 3 on the first optical transmission device 210 side, or may be a polarization state in other directions, which is not limited in the embodiment of the present application.

[0169] In this case, the second coupler 224 is used to separate the unmodulated optical signal 3 after polarization control. Exemplarily, the second coupler 224 is used to receive the unmodulated optical signal 3 after polarization control from the second polarization control module 227 through the third circulator 225, and then perform separation processing. For example, the second coupler 224 is used to separate the unmodulated optical signal 3 after polarization control into at least an unmodulated optical signal 6 and an unmodulated optical signal 7. For another example, the second coupler 224 is used to separate the unmodulated optical signal 3 after polarization control into at least an unmodulated optical signal 6, an unmodulated optical signal 7 and an unmodulated optical signal 5. For another example, the second coupler 224 is used to separate the unmodulated optical signal 3 after polarization control into an unmodulated optical signal 5. Among them, the unmodulated optical signal 6 can refer to the introduction of the second transmitting module 226, the unmodulated optical signal 7 can refer to the introduction of the second circulator 221, and the unmodulated optical signal 5 is used for coherent detection of the first modulated optical signal, specifically refer to the introduction of the second receiving module 222, which will not be repeated here. Since the unmodulated optical signal 6, the unmodulated optical signal 7 and the unmodulated optical signal 5 are separated from the unmodulated optical signal 3 after polarization control, the unmodulated optical signal 6, the unmodulated optical signal 7 and the unmodulated optical signal 5 have the same polarization state as the unmodulated optical signal 3 after polarization control, and are also optical signals after polarization control.

[0170] The second receiving module 222 is used to receive the first modulated optical signal from the first optical transmission device 210. Figure 3b As shown, the second receiving module 222 is used to receive the first modulated optical signal from the first circulator 214 through the second circulator 221. Among them, the first modulated optical signal is obtained by modulating the unmodulated optical signal 2, and the details can be referred to the introduction of the first transmitting module 213. The unmodulated optical signal 2 and the unmodulated optical signal 3 are obtained by separating the same optical signal (i.e., the above-mentioned unmodulated optical signal 1), and the details can be referred to the introduction of the first coupler 212, which will not be repeated here. Exemplarily, the second receiving module 222 is also used for coherent detection, such as using the unmodulated optical signal 5 to perform coherent detection on the first modulated optical signal.

[0171] In this way, the local oscillator light used for coherent detection is the unmodulated optical signal 5 after polarization control. Since the unmodulated optical signal 5 has higher energy in the desired polarization state, the influence of random polarization state changes is eliminated or reduced, so the accuracy of coherent detection is improved.

[0172] Optionally, the second polarization control module 227 is also connected to the second transmitting module 226 through the third circulator 225. Figure 3b As shown, for the third circulator 225 , three ports of the third circulator 225 are connected to the second coupler 224 , the second transmitting module 226 , and the second polarization control module 227 , respectively.

[0173] The second polarization control module 227 is also used for polarization control of the second modulated optical signal. Figure 3b As shown, in the case where the unmodulated optical signal 6 is separated, the second coupler 224 is used to send the unmodulated optical signal 6 to the second transmitting module 226 to modulate the second modulated optical signal. For details, please refer to the introduction of the second transmitting module 226, which will not be repeated here. The second polarization control module 227 is also used to receive the second modulated optical signal from the second transmitting module 226 through the third circulator 225, control the polarization of the second modulated optical signal, and send the second modulated optical signal after polarization control to the fourth circulator 215 of the first optical transmission device 210.

[0174] In this way, for the first receiving module 216, the modulated optical signal used for coherent detection is an optical signal that has been polarization-controlled and has more energy in the desired polarization direction. Among them, the second modulated optical signal after polarization control can have the same polarization state as the unmodulated optical signal 7 after polarization control. In the case where the unmodulated optical signal 7 is also polarized and controlled on the first optical transmission device 210 side, the local oscillator light (i.e., the above-mentioned unmodulated optical signal 7) that the first receiving module 216 performs coherent detection has the same polarization state as the second modulated optical signal. In this way, after the first receiving module 216 performs coherent detection, the electrical signal 2 can be obtained. The first DSP module 217 can obtain information 2 based on the electrical signal 2 without the need for polarization demultiplexing processing, thereby reducing system power consumption.

[0175] It should be understood that, when the coherent communication system 2000 includes the second polarization control module 227 , the single-mode optical fiber 240 may also be replaced with other connecting materials, such as ordinary optical fiber, to reduce system costs.

[0176] In some embodiments, Figure 4As shown, the first optical transmission device 210 further includes a first polarization control module 218, and the second optical transmission device 220 further includes a second polarization control module 227. The connection relationship and function between the first polarization control module 218 and other components can be seen in Figure 3a For the connection relationship and function between the second polarization control module 227 and other components, please refer to Figure 3b For unmodulated optical signals, Figure 4 In the communication system shown, the polarization of the unmodulated optical signal in the first transmission direction (i.e., the unmodulated optical signal 3) can be controlled, and the polarization of the unmodulated optical signal in the second transmission direction (i.e., the unmodulated optical signal 7) can be controlled, thereby eliminating or reducing the impact of random polarization state changes, which helps to improve the coherent detection performance of the system. Figure 4 The communication system shown can control the polarization of the first modulated optical signal in the first transmission direction, and can control the polarization of the second modulated optical signal in the second transmission direction, so that the two optical transmission devices (i.e., the first optical transmission device 210 and the second optical transmission device 220) do not need to perform polarization demultiplexing processing, which helps to reduce system power consumption.

[0177] The present application also provides a coherent optical transmission method 5000. The method is applicable to Figure 2a , Figure 2b , Figure 3a , Figure 3b or Figure 4 The communication system 2000 shown in FIG. Figure 5 As shown, the optical transmission method 5000 includes the following steps:

[0178] S501 : The first optical transmission device 210 sends an unmodulated optical signal 3 to the second optical transmission device 220 . Correspondingly, the second optical transmission device 220 receives the unmodulated optical signal 3 from the first optical transmission device 210 .

[0179] For example, see Figure 2a In the first optical transmission device 210, the fourth circulator 215 sends the unmodulated optical signal 3 to the third circulator 225 through the optical interface 2, the single-mode optical fiber 240 and the optical interface 4. Correspondingly, in the second optical transmission device 220, the third circulator 225 receives the unmodulated optical signal 3 through the optical interface 4.

[0180] For example, see Figure 2a In the first optical transmission device 210, the generation process of the unmodulated optical signal 3 is as follows:

[0181] The laser 211 generates an unmodulated optical signal 1. The first coupler 212 receives the unmodulated optical signal 1 from the laser 211 and separates the unmodulated optical signal 1 to obtain a separation result. The separation result includes one of the following:

[0182] The first item is unmodulated optical signal 2 and unmodulated optical signal 3.

[0183] The second item is the unmodulated optical signal 3.

[0184] The separation result can be referred to the introduction of the first coupler 212, which will not be repeated here. In the case of separating and obtaining the unmodulated optical signal 2, the first optical transmission device 210 performs the introduction of S511. In the case of separating and obtaining the unmodulated optical signal 3, the first coupler 212 sends the unmodulated optical signal 3 to the fourth circulator 215, and then transmits it to the second optical transmission device 220.

[0185] S502 , the second optical transmission device 220 separates the unmodulated optical signal 3 .

[0186] For example, see Figure 2a , the second coupler 224 receives the unmodulated optical signal 3 from the third circulator 225, and separates the unmodulated optical signal 3 to obtain a separation result. The separation result includes one of the following:

[0187] The first item, unmodulated optical signal 5, unmodulated optical signal 6 and unmodulated optical signal 7.

[0188] The second item is the unmodulated optical signal 5.

[0189] The third item, unmodulated optical signal 6 and unmodulated optical signal 7.

[0190] The separation results can be found in Figure 2a The introduction of the second coupler 224 in the embodiment will not be repeated here. In the case where the unmodulated optical signal 5 is separated, the second optical transmission device 220 executes S513. In the case where the unmodulated optical signal 6 is separated, the second optical transmission device 220 executes S503. In the case where the unmodulated optical signal 7 is separated, the second optical transmission device 220 executes S505. The introduction of S503 and S505 is as follows:

[0191] S503: The second optical transmission device 220 modulates the unmodulated optical signal 6 to obtain a second modulated optical signal.

[0192] For example, see Figure 2a The second transmitting module 226 receives the unmodulated optical signal 6 from the second coupler 224, modulates the unmodulated optical signal 6, and obtains a second modulated optical signal. For details, see Figure 2aThe introduction of the second transmitting module 226 will not be repeated here.

[0193] S504 : The second optical transmission device 220 sends a second modulated optical signal to the first optical transmission device 210 . Correspondingly, the first optical transmission device 210 receives the second modulated optical signal from the second optical transmission device 220 .

[0194] For example, see Figure 2a , the second transmitting module 226 sends the second modulated optical signal to the third circulator 225, and the third circulator 225 sends the second modulated optical signal to the optical interface 4, so that the second modulated optical signal is transmitted to the fourth circulator 215 of the first optical transmission device 210 through the single-mode optical fiber 240. Correspondingly, the fourth circulator 215 receives the second modulated optical signal through the optical interface 2.

[0195] S505 : The second optical transmission device 220 sends the unmodulated optical signal 7 to the first optical transmission device 210 . Accordingly, the first optical transmission device 210 receives the unmodulated optical signal 7 from the second optical transmission device 220 .

[0196] For example, see Figure 2a , the second coupler 224 sends the unmodulated optical signal 7 to the second circulator 221, and the second circulator 221 sends the unmodulated optical signal 7 to the optical interface 3, so that the unmodulated optical signal 7 is transmitted to the first circulator 214 of the first optical transmission device 210 through the single-mode optical fiber 230. Correspondingly, the first circulator 214 receives the unmodulated optical signal 7 through the optical interface 1.

[0197] Optionally, for the first optical transmission device 210, after executing S504 and S505, execute S506:

[0198] S506. The first optical transmission device 210 uses the unmodulated optical signal 7 to perform coherent detection on the second modulated optical signal.

[0199] For example, see Figure 2a , the first receiving module 216 receives the unmodulated optical signal 7 from the first circulator 214 as the local oscillator light. The first receiving module 216 also receives the second modulated optical signal from the fourth circulator 215, and uses the unmodulated optical signal 7 to perform coherent detection on the second modulated optical signal to obtain the electrical signal 2. For details, see Figure 2a Afterwards, the first DSP module 217 processes the electrical signal 2 to obtain information 2. For details, see Figure 2a The introduction of the first DSP module 217 will not be repeated here.

[0200] In the optical transmission method 5000 of the embodiment of the present application, the second optical transmission device 220 transmits the second modulated optical signal and the unmodulated optical signal 7 to the first optical transmission device 210, so the transmission paths of the second modulated optical signal and the unmodulated optical signal 7 are the same or close. Among them, the second modulated optical signal is obtained by modulating the unmodulated optical signal 6, and the unmodulated optical signal 6 and the unmodulated optical signal 7 are obtained by separating the same optical signal provided by the first optical transmission device 210, that is, the unmodulated optical signal 3 mentioned above. In addition, the transmission paths of the second modulated optical signal and the unmodulated optical signal 7 are the same or close, so there is no frequency difference between the two, and they are coherent light, thereby reducing or even eliminating phase noise.

[0201] The above only introduces the modulation, transmission and demodulation of the second modulated optical signal. Optionally, the following introduces the modulation, transmission and coherent detection of the first modulated optical signal. Figure 6 , the coherent optical transmission method 5000 of the embodiment of the present application further includes:

[0202] S511. The first optical transmission device 210 modulates the unmodulated optical signal 2 to obtain a first modulated optical signal.

[0203] For example, see Figure 2a In the case where the unmodulated optical signal 2 is separated, the first transmitting module 213 receives the unmodulated optical signal 2 from the first coupler 212, modulates the unmodulated optical signal 2, and obtains a first modulated optical signal. For details, see Figure 2a The introduction of the first transmitting module 213 is not repeated here.

[0204] S512 : The first optical transmission device 210 sends a first modulated optical signal to the second optical transmission device 220 . Correspondingly, the second optical transmission device 220 receives the first modulated optical signal from the first optical transmission device 210 .

[0205] For example, see Figure 2a , the first transmitting module 213 sends the first modulated optical signal to the first circulator 214, and the first circulator 214 sends the first modulated optical signal to the optical interface 1, so that the first modulated optical signal is transmitted to the second circulator 221 of the second optical transmission device 220 through the single-mode optical fiber 230. Correspondingly, the second circulator 221 receives the first modulated optical signal through the optical interface 3.

[0206] S513: The second optical transmission device 220 uses the unmodulated optical signal 5 to perform coherent detection on the first modulated optical signal.

[0207] For example, see Figure 2a, the second receiving module 222 receives the unmodulated optical signal 5 from the second coupler 224 as the local oscillator light. The second receiving module 222 also receives the first modulated optical signal from the second circulator 221, and uses the unmodulated optical signal 5 to perform coherent detection on the first modulated optical signal to obtain the electrical signal 1. Afterwards, the second DSP module 223 processes the electrical signal 1 to obtain the information 1.

[0208] In some embodiments, Figure 7 As shown, the coherent optical transmission method 5000 of the embodiment of the present application also includes:

[0209] S520 , the first optical transmission device 210 controls the polarization of the unmodulated optical signal 7 .

[0210] For example, see Figure 3a After receiving the unmodulated optical signal 7 through the optical interface 1, the first polarization control module 218 converts the polarization state of the unmodulated optical signal 7 into a desired polarization state. For details, see Figure 3a The introduction of the first polarization control module 218 will not be repeated here.

[0211] When S520 is executed, S506 may be replaced by S506a:

[0212] S506a: The first optical transmission device 210 uses the unmodulated optical signal 7 after polarization control to perform coherent detection on the second modulated optical signal.

[0213] Exemplarily, the first receiving module 216 receives the unmodulated optical signal 7 after polarization control from the first polarization control module 218 through the first circulator 214 as the local oscillator light, and performs coherent detection on the second modulated optical signal.

[0214] In this way, the local oscillator light used for coherent detection is the unmodulated optical signal 7 after polarization control. Since the unmodulated optical signal 7 has higher energy in the desired polarization state, the influence of random polarization state changes is eliminated or reduced, so the accuracy of coherent detection is improved.

[0215] Optional, such as Figure 8 As shown, the coherent optical transmission method 5000 of the embodiment of the present application also includes:

[0216] S521. The first optical transmission device 210 controls polarization of the first modulated optical signal.

[0217] For example, see Figure 3aAfter the first transmitting module 213 generates the first modulated optical signal, it sends the first modulated optical signal to the first polarization control module 218 through the first circulator 214. The first polarization control module 218 controls the polarization of the first modulated optical signal so that the polarization-controlled first modulated optical signal has more energy in the desired polarization direction.

[0218] When S521 is executed, S512 may be replaced by S512a:

[0219] S512a: The first optical transmission device 210 sends the polarization-controlled first modulated optical signal to the second optical transmission device 220. Correspondingly, the second optical transmission device 220 receives the polarization-controlled first modulated optical signal from the first optical transmission device 210.

[0220] For example, see Figure 3a The first polarization control module 218 transmits the polarization-controlled first modulated optical signal through the optical interface 1 and the single-mode optical fiber 230. Correspondingly, the second circulator 221 receives the polarization-controlled first modulated optical signal through the optical interface 3 and provides the polarization-controlled first modulated optical signal to the second receiving module 222.

[0221] When the second optical transmission device 220 also performs polarization control on the unmodulated optical signal 3, the local oscillator light (i.e., the unmodulated optical signal 5) for coherent detection by the second receiving module 222 is the same as the polarization state of the first modulated optical signal, so that the second receiving module 222 can obtain the electrical signal 1 after performing coherent detection. The second DSP module 223 can obtain the information 1 based on the electrical signal 1 without performing polarization demultiplexing processing, thereby reducing system power consumption.

[0222] In some embodiments, Fig. 9 As shown, the optical transmission method 5000 of the embodiment of the present application further includes:

[0223] S530 : The second optical transmission device 220 controls the polarization of the unmodulated optical signal 3 .

[0224] For example, see Figure 3b After receiving the unmodulated optical signal 3 through the optical interface 4, the second polarization control module 227 converts the polarization state of the unmodulated optical signal 3 into a desired polarization state. For details, see Figure 3b The introduction of the second polarization control module 227 will not be repeated here.

[0225] When S530 is executed, S502 may be replaced by S502a:

[0226] S502a, the second optical transmission device 220 separates the unmodulated optical signal 3 after polarization control.

[0227] Since the unmodulated optical signal 6, the unmodulated optical signal 7 and the unmodulated optical signal 5 are separated from the unmodulated optical signal 3 after polarization control, the polarization state of the unmodulated optical signal 6, the unmodulated optical signal 7 and the unmodulated optical signal 5 is the same as that of the unmodulated optical signal 3 after polarization control.

[0228] Optionally, for the second optical transmission device 220, when the unmodulated optical signal 5 is separated, S513 may be replaced by S513a:

[0229] S513a. The second optical transmission device 220 uses the unmodulated optical signal 5 after polarization control to perform coherent detection on the first modulated optical signal.

[0230] Exemplarily, the second receiving module 222 receives the first modulated optical signal from the first optical transmission device 210 through the second circulator 221, and uses the unmodulated optical signal 5 after polarization control to perform coherent detection on the first modulated optical signal. For details, see Figure 3b The introduction of the second receiving module 222 will not be repeated here.

[0231] In this way, the local oscillator light used for coherent detection is the unmodulated optical signal 5 after polarization control. Since the unmodulated optical signal 5 has higher energy in the desired polarization state, the influence of random polarization state changes is eliminated or reduced, so the accuracy of coherent detection is improved.

[0232] Optional, such as Fig.10 As shown, the optical transmission method 5000 of the embodiment of the present application further includes:

[0233] S531. The second optical transmission device 220 controls polarization of the second modulated optical signal.

[0234] For example, see Figure 3b After the second transmitting module 226 generates the second modulated optical signal, it sends the second modulated optical signal to the second polarization control module 227 through the third circulator 225. The second polarization control module 227 controls the polarization of the second modulated optical signal so that the second modulated optical signal after polarization control has more energy in the desired polarization direction.

[0235] When S531 is executed, S504 may be replaced by S504a:

[0236] S504a: The second optical transmission device 220 sends the second modulated optical signal after polarization control to the first optical transmission device 210. Correspondingly, the first optical transmission device 210 receives the second modulated optical signal from the second optical transmission device 220 after polarization control.

[0237] For example, see Figure 3bThe second polarization control module 227 transmits the second modulated optical signal after polarization control through the optical interface 4 and the single-mode optical fiber 240. Correspondingly, the fourth circulator 215 receives the second modulated optical signal after polarization control through the optical interface 2, and provides the second modulated optical signal after polarization control to the first receiving module 216.

[0238] In this way, the second modulated optical signal after polarization control can have the same polarization state as the unmodulated optical signal 7 after polarization control. In the case where the unmodulated optical signal 7 is also polarized by the first optical transmission device 210, the local oscillator light (i.e., the unmodulated optical signal 7) and the second modulated optical signal that are coherently detected by the first receiving module 216 are the same in polarization state, so that the first receiving module 216 can obtain the electrical signal 2 after coherent detection. The first DSP module 217 can obtain the information 2 based on the electrical signal 2 without polarization demultiplexing processing, thereby reducing system power consumption.

[0239] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application shall be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A first optical transmission device, characterized in that: include: a first circulator, configured to receive a second unmodulated optical signal from a second optical transmission device; a first receiving module connected to the first circulator, and configured to receive a second modulated optical signal from the second optical transmission device, and receive the second unmodulated optical signal from the first circulator, wherein the second modulated optical signal is obtained by modulating the first unmodulated optical signal, the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal, the first unmodulated optical signal and the second unmodulated optical signal are obtained by separating a third unmodulated optical signal, and the third unmodulated optical signal is an optical signal provided by the first optical transmission device to the second optical transmission device.

2. The device according to claim 1, characterized in that The first circulator is also connected to a second circulator, wherein the second optical transmission device includes the second circulator; The first circulator is used to receive the second unmodulated optical signal from the second optical transmission device, including: receiving the second unmodulated optical signal from the second circulator.

3. The device according to claim 1 or 2, characterized in that: Also includes: A first polarization control module connected to the first circulator; The first polarization control module is used to control the polarization of the second unmodulated optical signal.

4. The device according to claim 3, characterized in that The second unmodulated optical signal is used for performing coherent detection on the second modulated optical signal, including: the second unmodulated optical signal after polarization control is used for performing the coherent detection on the second modulated optical signal.

5. The device according to claim 3, characterized in that The first polarization control module is further used to control the polarization of a first modulated optical signal, wherein the first modulated optical signal is an optical signal sent by the first optical transmission device to the second optical transmission device.

6. The device according to claim 4, characterized in that The first polarization control module is further used to control the polarization of a first modulated optical signal, wherein the first modulated optical signal is an optical signal sent by the first optical transmission device to the second optical transmission device.

7. The device according to claim 5, characterized in that Also includes: The first transmitting module is connected to the first circulator, and is used for sending the first modulated optical signal to the first polarization control module through the first circulator.

8. The device according to claim 6, characterized in that Also includes: The first transmitting module is connected to the first circulator, and is used for sending the first modulated optical signal to the first polarization control module through the first circulator.

9. The device according to any one of claims 1 to 2, characterized in that: The first optical transmission device is an optical transmission device on the active antenna unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side; or, The first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

10. A second optical transmission device, characterized in that: include: a second coupler, configured to separate a third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal, wherein the third unmodulated optical signal is an optical signal provided by the first optical transmission device; A second transmitting module is connected to the second coupler and is used to transmit light to the first optical transmission device. send A second modulated optical signal, wherein the second modulated optical signal is obtained by modulating the first unmodulated optical signal; A second circulator is connected to the second coupler, and is used to receive the second unmodulated optical signal from the second coupler, and send the second unmodulated optical signal to the first optical transmission device, wherein the second unmodulated optical signal is used for coherent detection of the second modulated optical signal.

11. The device according to claim 10, characterized in that The second circulator is also connected to the first circulator, wherein the first optical transmission device includes the first circulator; The second circulator is used to send the second unmodulated optical signal to the first optical transmission device, including: sending the second unmodulated optical signal to the first circulator.

12. The device according to claim 10 or 11, characterized in that Also includes: The second polarization control module is connected to the second coupler and is used to control the polarization of the third unmodulated optical signal.

13. The device according to claim 12, characterized in that The second coupler is used to separate the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal, comprising: The polarization-controlled third unmodulated optical signal is separated into at least the first unmodulated optical signal and the second unmodulated optical signal.

14. The device according to claim 12, characterized in that The second coupler is further used to separate the third unmodulated optical signal after polarization control into a fifth unmodulated optical signal, wherein the fifth unmodulated optical signal is used for coherent detection of the first modulated optical signal, and the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

15. The device according to claim 13, characterized in that The second coupler is further used to separate the third unmodulated optical signal after polarization control into a fifth unmodulated optical signal, wherein the fifth unmodulated optical signal is used for coherent detection of the first modulated optical signal, and the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

16. The device according to claim 14, characterized in that Also includes: The second receiving module is connected to the second circulator and the second coupler respectively, and is used to receive the first modulated optical signal from the first optical transmission device through the second circulator, and receive the fifth unmodulated optical signal from the second coupler.

17. The device according to claim 15, characterized in that Also includes: The second receiving module is connected to the second circulator and the second coupler respectively, and is used to receive the first modulated optical signal from the first optical transmission device through the second circulator, and receive the fifth unmodulated optical signal from the second coupler.

18. The device according to claim 12, characterized in that The second polarization control module is also connected to the second transmitting module, and is used to control the polarization of the second modulated optical signal.

19. The device according to any one of claims 13 to 17, characterized in that The second polarization control module is also connected to the second transmitting module, and is used to control the polarization of the second modulated optical signal.

20. The device according to claim 18, characterized in that Also includes: The third circulator; The second polarization control module, connected to the second coupler, includes: The second polarization control module is connected to the second coupler through the third circulator; The second polarization control module is also connected to the second transmitting module, and includes: The second polarization control module is also connected to the second transmitting module through the third circulator.

21. The device according to claim 19, characterized in that Also includes: The third circulator; The second polarization control module, connected to the second coupler, includes: The second polarization control module is connected to the second coupler through the third circulator; The second polarization control module is also connected to the second transmitting module, and includes: The second polarization control module is also connected to the second transmitting module through the third circulator.

22. The device according to any one of claims 10 to 11, characterized in that The first optical transmission device is an optical transmission device on the active antenna unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side; or, The first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

23. A light transmission method, characterized in that: The method is applied to a first optical transmission device, the device comprising a first circulator and a first receiving module, and the method comprises: The first circulator receives a second unmodulated optical signal from a second optical transmission device; The first receiving module receives a second modulated optical signal from the second optical transmission device, and receives the second unmodulated optical signal from the first circulator, wherein the second modulated optical signal is obtained by modulating the first unmodulated optical signal, the second unmodulated optical signal is used to perform coherent detection on the second modulated optical signal, and the first unmodulated optical signal and the second unmodulated optical signal are obtained by separating a third unmodulated optical signal, and the third unmodulated optical signal is an optical signal provided by the first optical transmission device to the second optical transmission device.

24. The method according to claim 23, characterized in that The first circulator receives a second unmodulated optical signal from a second optical transmission device, comprising: The first circulator receives the second unmodulated optical signal from a second circulator, wherein the first circulator is also connected to the second circulator, and the second optical transmission device includes the second circulator.

25. The method according to claim 23 or 24, characterized in that The method further comprises: A first polarization control module controls polarization of the second unmodulated optical signal, wherein the device further comprises the first polarization control module, and the first polarization control module is connected to the first circulator.

26. The method according to claim 25, characterized in that The second unmodulated optical signal is used for performing coherent detection on the second modulated optical signal, including: the second unmodulated optical signal after polarization control is used for performing the coherent detection on the second modulated optical signal.

27. The method according to claim 25, characterized in that The method further comprises: The first polarization control module controls polarization of a first modulated optical signal, wherein the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

28. The method according to claim 26, characterized in that The method further comprises: The first polarization control module controls polarization of a first modulated optical signal, wherein the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

29. The method according to claim 27, characterized in that The method further comprises: The first transmitting module sends the first modulated optical signal to the first polarization control module through the first circulator. The device also includes the first transmitting module, and the first transmitting module is connected to the first circulator.

30. The method according to claim 28, characterized in that The method further comprises: The first transmitting module sends the first modulated optical signal to the first polarization control module through the first circulator. The device also includes the first transmitting module, and the first transmitting module is connected to the first circulator.

31. The method according to any one of claims 23 to 24, characterized in that The first optical transmission device is an optical transmission device on the active antenna unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side; or, The first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

32. A light transmission method, characterized in that: The method is applied to a second optical transmission device, the device comprising a second coupler, a second transmitting module and a second circulator, and the method comprises: The second coupler separates the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal, wherein the third unmodulated optical signal is an optical signal provided by the first optical transmission device; The second transmitting module sends a second modulated optical signal to the first optical transmission device, wherein the second modulated optical signal is obtained by modulating the first unmodulated optical signal; The second circulator receives the second unmodulated optical signal from the second coupler, and sends the second unmodulated optical signal to the first optical transmission device, wherein the second unmodulated optical signal is used for coherent detection of the second modulated optical signal.

33. The method according to claim 32, characterized in that The second circulator sends the second unmodulated optical signal to the first optical transmission device, comprising: The second circulator sends the second unmodulated optical signal to the first circulator, wherein the second circulator is also connected to the first circulator, and the first optical transmission device includes the first circulator.

34. The method according to claim 32 or 33, characterized in that The method further comprises: The second polarization control module controls the polarization of the third unmodulated optical signal, wherein the device further includes the second polarization control module, and the second polarization control module is connected to the second coupler.

35. The method according to claim 34, characterized in that The second coupler separates the third unmodulated optical signal into at least a first unmodulated optical signal and a second unmodulated optical signal, comprising: The second coupler separates the polarization-controlled third unmodulated optical signal into at least the first unmodulated optical signal and the second unmodulated optical signal.

36. The method according to claim 34, characterized in that The method further comprises: The second coupler separates the polarization-controlled third unmodulated optical signal into a fifth unmodulated optical signal, wherein the fifth unmodulated optical signal is used for coherent detection of the first modulated optical signal, and the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

37. The method according to claim 35, characterized in that The method further comprises: The second coupler separates the polarization-controlled third unmodulated optical signal into a fifth unmodulated optical signal, wherein the fifth unmodulated optical signal is used for coherent detection of the first modulated optical signal, and the first modulated optical signal is an optical signal transmitted from the first optical transmission device to the second optical transmission device.

38. The method according to claim 36, characterized in that The method further comprises: The second receiving module receives the first modulated optical signal from the first optical transmission device through the second circulator, and receives the fifth unmodulated optical signal from the second coupler, wherein the device also includes the second receiving module, and the second receiving module is connected to the second circulator and the second coupler respectively.

39. The method according to claim 37, characterized in that The method further comprises: The second receiving module receives the first modulated optical signal from the first optical transmission device through the second circulator, and receives the fifth unmodulated optical signal from the second coupler, wherein the device also includes the second receiving module, and the second receiving module is connected to the second circulator and the second coupler respectively.

40. The method according to claim 34, characterized in that The method further comprises: The second polarization control module controls the polarization of the second modulated optical signal, wherein the second polarization control module is also connected to the second transmitting module.

41. The method according to any one of claims 35 to 39, characterized in that The method further comprises: The second polarization control module controls the polarization of the second modulated optical signal, wherein the second polarization control module is also connected to the second transmitting module.

42. The method according to any one of claims 32 to 33, characterized in that The first optical transmission device is an optical transmission device on the active antenna unit AAU side, and the second optical transmission device is an optical transmission device on the baseband unit BBU side; or, The first optical transmission device is an optical transmission device on the BBU side, and the second optical transmission device is an optical transmission device on the AAU side.

43. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a program, and when the program is called by a processor, the method according to any one of claims 23 to 31 or claims 32 to 42 is executed.

44. A computer program product comprising instructions, characterized in that When the computer program product is called by a processor, the method according to any one of claims 23 to 31 or claims 32 to 42 is executed.

45. A communication system, characterized in that: It comprises the first optical transmission device as claimed in any one of claims 1 to 9, and the second optical transmission device as claimed in any one of claims 10 to 22.

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