Laser communication method, laser communication receiving end, transmitting end and laser communication system

Abstract

This disclosure provides a laser communication method, a laser communication receiver, a transmitter, and a laser communication system. The method applied at the receiver includes: receiving a target light signal emitted by the transmitter using a first telescope; processing the target light signal using a first polarization beam splitter to obtain first polarized light and second polarized light; processing any one of the first polarized light and second polarized light using a first optical wave splitter to obtain multiple first sub-signals with different wavelengths; processing two first sub-signals with the same wavelength using a balanced detection device to obtain a transmission sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths; and processing the multiple transmission sub-signals using a digital signal processor to obtain a transmission signal.

Description

Technical Field

[0001] This disclosure relates to the field of laser communication technology, and more specifically, to a laser communication method applied at a receiver and a transmitter, a laser communication receiver, a laser communication transmitter, and a laser communication system. Background Technology

[0002] Coherent laser communication systems modulate the signal to be transmitted onto an optical carrier and then transmit it. The receiving end provides a local oscillator light with the same frequency, polarization state, and phase as the signal light. The two are mixed and then coherently detected and demodulated. This system has advantages such as high receiving sensitivity, low susceptibility to background light, and multiple modulation formats and detection and demodulation schemes. It is a major component of current space laser communication systems.

[0003] However, in coherent laser communication, the signal light and the local oscillator light originate from two different lasers, resulting in random phase fluctuations. The receiver needs to compensate for the phase or use a phase-locked loop to adjust it, which not only increases the complexity of the system but also affects the sensitivity of the laser communication system. Summary of the Invention

[0004] In view of this, embodiments of the present disclosure provide a laser communication method, a laser communication receiver, a laser communication transmitter, and a laser communication system, respectively applied to a receiver and a transmitter.

[0005] The first aspect of this disclosure provides a laser communication method applied to a receiving end communicatively connected to a transmitting end, comprising:

[0006] The first telescope is used to receive the target light signal emitted by the aforementioned transmitter. The target light signal is obtained by splitting the initial light source signal emitted by the same laser by the aforementioned transmitter, and then combining the split light signal with the other split light signal after phase modulation.

[0007] The target optical signal is processed using a first polarization beam splitter to obtain first polarized light and second polarized light.

[0008] For any one of the first polarized light and the second polarized light, the polarized light is processed by the first optical demultiplexer to obtain multiple first sub-signals with different wavelengths;

[0009] For each pair of first sub-signals with the same wavelength, the two first sub-signals are processed by a balanced detection device to obtain a transmission sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths.

[0010] The above-mentioned transmission sub-signals are processed by a digital signal processor to obtain the above-mentioned transmission signal.

[0011] According to embodiments of this disclosure, before the first polarization beam splitter processes the target optical signal, the method further includes:

[0012] The polarization state of the target optical signal is adjusted using a polarization controller to obtain the adjusted target optical signal.

[0013] According to embodiments of this disclosure, before processing the first polarized light using the first optical demultiplexer, the method further includes:

[0014] The polarization state of the first polarized light is adjusted by a polarization rotator to obtain the adjusted first polarized light. The adjusted first polarized light is then processed by the first optical splitter to obtain multiple first sub-signals with different wavelengths.

[0015] The process includes, before processing the second polarized light using the first optical splitter, the following:

[0016] The second polarized light is processed by an optical amplifier to obtain amplified second polarized light, which is then processed by the first optical demultiplexer to obtain multiple first sub-signals with different wavelengths.

[0017] According to embodiments of this disclosure, the balance detection device includes a mixer and a balance detector;

[0018] The above-mentioned use of a balance detection device to process the two first sub-signals to obtain the transmission sub-signal includes:

[0019] The two first signals with the same wavelength are processed by the mixer described above to obtain a mixed optical signal;

[0020] The above-mentioned balanced detector is used to process the above-mentioned mixed optical signal to obtain a target electrical signal characterizing the above-mentioned transmission sub-signal, so that the above-mentioned digital signal processor processes multiple above-mentioned target electrical signals to obtain the above-mentioned transmission signal.

[0021] A second aspect of this disclosure provides a coherent laser communication method applied to a transmitter connected in communication with a receiver, comprising:

[0022] The initial light source signal generated by the laser is processed using a second polarization beam splitter to obtain third and fourth polarized light.

[0023] The third polarized light is processed using a second optical demultiplexer to obtain multiple second signals with different wavelengths.

[0024] For each of the above-mentioned second sub-signals, a phase modulator is used to process the transmission sub-signals with the same wavelength and the above-mentioned second sub-signals to obtain the modulated second sub-signals, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths;

[0025] The initial optical signal is obtained by processing multiple modulated second-sub-signals using an optical combiner.

[0026] The target optical signal is obtained by processing the initial optical signal and the fourth polarized light using a polarization beam combiner.

[0027] The target light signal was emitted using the second telescope.

[0028] According to embodiments of this disclosure, the above-described method of using a phase modulator to process a transmission sub-signal with the same wavelength and the second sub-signal to obtain a modulated second sub-signal includes:

[0029] The modulation voltage sequence is determined based on the aforementioned transmission sub-signals;

[0030] When the above-mentioned modulation voltage sequence is applied to the above-mentioned phase modulator, the above-mentioned second sub-signal is processed by the above-mentioned phase modulator to obtain the above-mentioned modulated second sub-signal, wherein the format of the above-mentioned modulated second sub-signal includes binary phase shift keying or differential phase shift keying.

[0031] According to embodiments of this disclosure, before processing the initial light source signal using the second polarization beam splitter, the method further includes:

[0032] The initial light source signal is processed using an optical frequency comb to obtain a multi-wavelength light source signal, which is then processed using the second polarization beam splitter.

[0033] A third aspect of this disclosure provides a laser communication receiver, which is communicatively connected to a transmitter. The receiver includes:

[0034] The first telescope is used to receive the target light signal emitted by the aforementioned transmitter.

[0035] The first polarization beam splitter is used to process the target optical signal to obtain first polarized light and second polarized light.

[0036] The first optical demultiplexer is used to process either the first polarized light or the second polarized light to obtain multiple first sub-signals with different wavelengths.

[0037] A balanced detection device is used to process two first sub-signals with the same wavelength to obtain a transmission sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths.

[0038] A digital signal processor is used to process multiple of the above-mentioned transmission sub-signals to obtain the above-mentioned transmission signal.

[0039] A fourth aspect of this disclosure provides a laser communication transmitter, which is communicatively connected to a receiver. The transmitter includes:

[0040] A laser is used to generate an initial light source signal;

[0041] The second polarization beam splitter is used to process the initial light source signal to obtain the third polarized light and the fourth polarized light.

[0042] The second optical demultiplexer is used to process the third polarized light mentioned above to obtain multiple second signals with different wavelengths;

[0043] Multiple phase modulators, each of the aforementioned phase modulators being used to process the transmission sub-signal and the aforementioned second sub-signal with the same wavelength to obtain a modulated second sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths;

[0044] An optical combiner is used to process multiple modulated second-segment signals to obtain an initial optical signal.

[0045] A polarization beam combiner is used to process the initial optical signal and the fourth polarized light to obtain the target optical signal.

[0046] The second telescope is used to transmit the aforementioned target light signal.

[0047] A fifth aspect of this disclosure provides a laser communication system, including: a receiver as described above; and a transmitter as described above.

[0048] According to embodiments of this disclosure, a target optical signal emitted from a transmitter is received. This target optical signal is obtained by splitting an initial light source signal emitted by the same laser, performing phase modulation on one of the split optical signals, and then combining it with another split optical signal. The receiver then uses a first polarization beam splitter to split the target optical signal into multiple wavelengths for wavelength division processing. This allows for the analysis of the transmission sub-signals in each wavelength's first sub-signal, ultimately achieving multi-carrier communication analysis. The high transmission rate of multi-carrier communication, combined with the beam splitting and phase modulation methods at the transmitter, enables coherent detection of the laser communication from zero difference, improving the sensitivity of the coherent laser communication system. Attached Figure Description

[0049] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0050] Figure 1 A flowchart illustrating a laser communication method applied to a receiving end according to an embodiment of the present disclosure is shown schematically;

[0051] Figure 2 A flowchart illustrating a laser communication method applied to a transmitter according to an embodiment of the present disclosure is shown schematically.

[0052] Figure 3 A schematic block diagram of a receiving end according to an embodiment of the present disclosure is shown; and

[0053] Figure 4 A schematic block diagram of a transmitter according to an embodiment of the present disclosure is shown. Detailed Implementation

[0054] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0055] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0056] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0057] When using expressions such as "at least one of A, B, and C", they should generally be interpreted in accordance with the meaning that is commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B, and C, etc.).

[0058] Figure 1 A flowchart illustrating a laser communication method applied to a receiving end according to an embodiment of the present disclosure is shown schematically.

[0059] This coherent laser communication method is applied to the receiving end, which is connected to the transmitting end for communication, such as... Figure 1 As shown, the laser communication method includes operations S101 to S105.

[0060] In operation S101, the first telescope is used to receive the target light signal emitted by the transmitter. The target light signal is obtained by splitting the initial light source signal emitted by the same laser by the transmitter, and then combining the split light signal with the other split light signal after phase modulation.

[0061] In operation S102, the target optical signal is processed using the first polarization beam splitter to obtain first polarized light and second polarized light.

[0062] In operation S103, for any polarized light in the first polarized light and the second polarized light, the polarized light is processed by the first optical splitter to obtain multiple first sub-signals with different wavelengths.

[0063] In operation S104, for each pair of first sub-signals with the same wavelength, the two first sub-signals are processed by a balanced detection device to obtain a transmission sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths.

[0064] In operation S105, multiple transmission sub-signals are processed by a digital signal processor to obtain the transmission signal.

[0065] According to embodiments of this disclosure, the first telescope may refer to an optical telescope, which can be used to acquire optical signals emitted by the transmitting end. A transmission signal transmitted by the transmitting end is coupled into the target optical signal. The transmission signal can characterize data that needs to be transmitted between the receiving end and the transmitting end, such as text, passwords, etc.

[0066] According to embodiments of this disclosure, a first polarization beam splitter (PBS) performs polarization beam splitting processing on the target optical signal to obtain two beams with orthogonal polarization states, namely a first polarized light with X polarization state and a second polarized light with Y polarization state. Both the first polarized light and the second polarized light are processed by a first optical beam splitter to obtain a first sub-signal corresponding to multiple different wavelengths of the first polarized light and a first sub-signal corresponding to multiple different wavelengths of the second polarized light.

[0067] According to embodiments of this disclosure, multiple first sub-signals corresponding to different polarized light are paired by wavelength. Two first sub-signals of the same wavelength are sent to a balanced detection device for beat frequency processing to convert the optical signal into an electrical signal, thereby obtaining the detection data of that wavelength, i.e., the transmission sub-signal. Finally, the multiple transmission sub-signals are demodulated by a digital signal processor (DSP) to obtain the complete transmission signal.

[0068] According to embodiments of this disclosure, a target optical signal emitted from a transmitter is received. This target optical signal is obtained by splitting an initial light source signal emitted by the same laser, performing phase modulation on one of the split optical signals, and then combining it with another split optical signal. The receiver then uses a first polarization beam splitter to split the target optical signal into multiple wavelengths for wavelength division processing. This allows for the analysis of the transmission sub-signals in each wavelength's first sub-signal, ultimately achieving multi-carrier communication analysis. The high transmission rate of multi-carrier communication, combined with the beam splitting and phase modulation methods at the transmitter, enables coherent detection of the laser communication from zero difference, improving the sensitivity of the coherent laser communication system.

[0069] According to embodiments of this disclosure, before the first polarization beam splitter processes the target optical signal, the following operation is further included:

[0070] The polarization state of the target optical signal is adjusted using a polarization controller to obtain the adjusted target optical signal.

[0071] According to embodiments of this disclosure, a polarization controller (PC) can fine-tune the polarization state of a target optical signal, thereby avoiding crosstalk between the X-polarization state and the Y-polarization state in the target optical signal, and thus obtaining a target optical signal with fine-tuned polarization state. The use of a polarization controller helps to improve the accuracy of the resolution results of the transmitted signal.

[0072] According to embodiments of this disclosure, before processing the first polarized light using the first optical demultiplexer, the following operation is further included:

[0073] The polarization state of the first polarized light is adjusted using a polarization rotator to obtain the adjusted first polarized light. The adjusted first polarized light is then processed by a first optical splitter to obtain multiple first sub-signals with different wavelengths.

[0074] According to embodiments of this disclosure, a polarization beam rotator (PBR) can rotate the polarization state of a first polarized light by 90 degrees so that the first polarized light after the polarization state rotation has the same polarization state as the second polarized light, thereby achieving accurate analytical detection of the transmitted signal in the target optical signal.

[0075] According to embodiments of this disclosure, before processing the second polarized light using the first optical demultiplexer, the method further includes:

[0076] The second polarized light is processed by an optical amplifier to obtain amplified second polarized light, which is then processed by a first optical demultiplexer to obtain multiple first sub-signals with different wavelengths.

[0077] According to embodiments of this disclosure, an erbium-doped optical fiber amplifier (EDFA) can amplify the second polarized light so that a first optical demultiplexer can perform wavelength division processing on the amplified second polarized light.

[0078] According to embodiments of this disclosure, the balance detection device includes a mixer and a balance photo detector (BPD).

[0079] According to embodiments of this disclosure, the two first sub-signals are processed using a balance detection device to obtain a transmission sub-signal, including the following operations:

[0080] A mixer is used to process two first-wavelength signals with the same wavelength to obtain a mixed optical signal.

[0081] By using a balanced detector to process the mixed optical signal, a target electrical signal characterizing the transmitted sub-signal is obtained, which enables a digital signal processor to process multiple target electrical signals to obtain the transmitted signal.

[0082] According to an embodiment of this disclosure, two first sub-signals with the same wavelength are input together into a 180° mixer to output a mixed optical signal. The mixed optical signal is then input into a balanced detector, which can convert the optical signal into an electrical signal, thereby obtaining the target electrical signal of the transmission sub-signal. The transmission signal is obtained by demodulating and processing multiple target electrical signals corresponding to different transmission sub-signals using a digital signal processor.

[0083] Figure 2 A flowchart illustrating a laser communication method applied to a transmitter according to an embodiment of the present disclosure is shown schematically.

[0084] Coherent laser communication methods are applied at the transmitting end, which is connected to the receiving end for communication, such as... Figure 2 As shown, the method includes operations S201 to S206.

[0085] In operation S201, the initial light source signal generated by the laser is processed by the second polarization beam splitter to obtain the third polarized light and the fourth polarized light.

[0086] In operation S202, the third polarized light is processed by the second optical demultiplexer to obtain multiple second sub-signals with different wavelengths.

[0087] In operation S203, for each second sub-signal, a phase modulator is used to process the transmission sub-signal and the second sub-signal with the same wavelength to obtain the modulated second sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths.

[0088] In operation S204, multiple modulated second sub-signals are processed using an optical combiner to obtain the initial optical signal.

[0089] In operation S205, the initial optical signal and the fourth polarized light are processed by a polarization beam combiner to obtain the target optical signal.

[0090] In operation S206, the target light signal is emitted using the second telescope.

[0091] According to embodiments of this disclosure, the laser may include an external cavity laser (ECL).

[0092] According to embodiments of this disclosure, a laser continuously emits an optical carrier with a narrow linewidth range (i.e., an initial light source signal). Processing this initial light source signal using a second polarization beam splitter splits it into third polarized light (X-polarization state) and fourth polarized light (Y-polarization state) with orthogonal polarization states. Processing the third polarized light (which can serve as the optical carrier) using the second optical beam splitter yields multiple second sub-signals with different wavelengths. For each second sub-signal, a phase modulator modulates a transport sub-signal with the same wavelength as that second sub-signal onto it, thereby obtaining a modulated second sub-signal (signal light).

[0093] According to embodiments of this disclosure, after each second sub-signal is modulated, multiple modulated second sub-signals can be combined using an optical combiner to obtain an initial optical signal. The initial optical signal and the fourth polarized light (the third polarized light can be used as the local oscillator) can be combined using a polarization beam combiner to obtain the target optical signal. Finally, the target optical signal is transmitted to the receiving end using a second telescope for data transmission.

[0094] According to embodiments of this disclosure, after splitting the initial light source signal generated by the same laser using a second polarization beam splitter, one of the polarized beams is used for waveband carrier communication using a wave splitter, a phase modulator, and a wave combiner. The second optical signal loaded with the transmission signal and the second polarized beam are then combined using a polarization beam combiner and transmitted, realizing self-zero difference coherent detection based on polarization transmission, improving the sensitivity of the coherent laser communication system. At the same time, the use of multi-carrier communication reduces interference between adjacent channels and increases the data transmission rate of laser communication.

[0095] According to embodiments of this disclosure, a phase modulator is used to process a transmission sub-signal and a second sub-signal with the same wavelength to obtain a modulated second sub-signal, including the following operations:

[0096] The modulation voltage sequence is determined based on the transmitted sub-signal. When the modulation voltage sequence is applied to the phase modulator, the second sub-signal is processed by the phase modulator to obtain the modulated second sub-signal. The format of the modulated second sub-signal includes binary phase shift keying (BPSK) or differential phase shift keying (DPSK).

[0097] According to an embodiment of this disclosure, before loading the transmission sub-signal onto the second sub-signal, a modulation voltage sequence needs to be determined based on the transmission sub-signal, and the modulation voltage sequence is loaded onto the corresponding phase modulator so that the phase modulator modulates the second sub-signal based on the modulation voltage sequence to obtain the modulated second sub-signal.

[0098] In one exemplary embodiment, the transmission sub-signal can be viewed as a series of binary strings, and a voltage value corresponding to the corresponding character is generated, thereby generating a modulated voltage sequence of the transmission sub-signal.

[0099] According to embodiments of this disclosure, before processing the initial light source signal using the second polarization beam splitter, the following operations are further included:

[0100] The initial light source signal is processed using an optical frequency comb to obtain a multi-wavelength light source signal, which is then processed using a second polarization beam splitter.

[0101] According to embodiments of this disclosure, an initial light source signal is processed using an optical frequency comb (OFC) to obtain a multi-wavelength light source signal. The frequency interval between different wavelengths of light in the multi-wavelength light source signal is fixed and the coherence is good, which can improve the communication quality of laser communication.

[0102] Figure 3 A schematic block diagram of a receiver according to an embodiment of the present disclosure is shown.

[0103] The receiver 100 and transmitter 200 of the laser communication are connected in a communication manner, such as... Figure 3 As shown, the receiver 100 includes a first telescope 110, a first polarization beam splitter 120, a first optical beam splitter 130, a balanced detection device 140, and a digital signal processor 150.

[0104] The first telescope 110 is used to receive the target light signal emitted by the transmitter 200.

[0105] The first polarization beam splitter 120 is used to process the target optical signal to obtain first polarized light and second polarized light.

[0106] The first optical splitter 130 is used to process either the first polarized light or the second polarized light to obtain multiple first sub-signals with different wavelengths.

[0107] The balanced detection device 140 is used to process the first sub-signals with the same wavelength for every two wavelengths to obtain the transmission sub-signals, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths.

[0108] The digital signal processor 150 is used to process multiple transmission sub-signals to obtain the transmission signal.

[0109] According to embodiments of this disclosure, by receiving a target optical signal emitted from the transmitter 200, which is obtained by splitting an initial light source signal emitted by the same laser 210, and then combining one of the split optical signals with another split optical signal after phase modulation, the receiver 100 uses a first polarization beam splitter 120 to split the target optical signal into multiple wavelengths for wavelength division processing. This allows for the analysis of the transmission sub-signals in the first sub-signal of each wavelength, ultimately achieving the analysis processing for multi-carrier communication. The high transmission rate of multi-carrier communication, combined with the beam splitting and phase modulation method in the transmitter 200, enables coherent detection of laser communication with zero difference, improving the sensitivity of the coherent laser communication system.

[0110] According to embodiments of the present disclosure, the receiver 100 further includes at least one of a polarization controller 160, a polarization rotator 170, and an optical amplifier 180.

[0111] The polarization controller 160 is used to adjust the polarization state of the target optical signal to obtain the adjusted target optical signal.

[0112] The polarization rotator 170 is used to adjust the polarization state of the first polarized light to obtain the adjusted first polarized light, which is then processed by the first optical splitter 130 to obtain multiple first sub-signals with different wavelengths.

[0113] Optical amplifier 180 is used to process the second polarized light to obtain amplified second polarized light, which is then processed by first optical demultiplexer 130 to obtain multiple first sub-signals with different wavelengths.

[0114] According to embodiments of the present disclosure, the balance detection device 140 includes a mixer 141 and a balance detector 142.

[0115] Mixer 141 is used to process two first sub-signals with the same wavelength to obtain a mixed optical signal.

[0116] The balanced detector 142 is used to process the mixed optical signal to obtain the target electrical signal characterizing the transmission sub-signal, so that the digital signal processor 150 processes multiple target electrical signals to obtain the transmission signal.

[0117] Figure 4 A schematic block diagram of a transmitter 200 according to an embodiment of the present disclosure is shown.

[0118] The laser communication transmitter 200 and receiver 100 are communicatively connected, such as... Figure 4 As shown, the transmitter 200 includes a laser 210, a second polarization beam splitter 220, a second optical beam splitter 230, multiple phase modulators 240, an optical beam combiner 250, a polarization beam combiner 260, and a second telescope 270.

[0119] Laser 210 is used to generate an initial light source signal.

[0120] The second polarization beam splitter 220 is used to process the initial light source signal to obtain the third polarized light and the fourth polarized light.

[0121] The second optical demultiplexer 230 is used to process the third polarized light to obtain multiple second sub-signals with different wavelengths.

[0122] Multiple phase modulators 240 are used to process the transmission sub-signal and the second sub-signal with the same wavelength to obtain a modulated second sub-signal, wherein the transmission signal includes multiple transmission sub-signals with different wavelengths.

[0123] Optical combiner 250 is used to process multiple modulated second-segment signals to obtain the initial optical signal.

[0124] The polarization combiner 260 is used to process the initial optical signal and the fourth polarized light to obtain the target optical signal.

[0125] The second telescope, 270, is used to transmit target light signals.

[0126] According to embodiments of this disclosure, after the initial light source signal generated by the same laser 210 is split by the second polarization beam splitter 220, one of the polarized beams is used for waveband carrier communication using a wave splitter, a phase modulator 240, and a wave combiner. The second optical signal loaded with the transmission signal and the second polarized beam are combined by the polarization beam combiner 260 and then transmitted. This achieves coherent detection based on polarization transmission with zero difference, improving the sensitivity of the coherent laser communication system. At the same time, the use of multi-carrier communication reduces interference between adjacent channels and increases the data transmission rate of laser communication.

[0127] According to embodiments of this disclosure, a phase modulator 240 is used to process a transmission sub-signal and a second sub-signal with the same wavelength to obtain a modulated second sub-signal, including the following operations:

[0128] The modulation voltage sequence is determined based on the transmitted sub-signal. When the modulation voltage sequence is applied to the phase modulator 240, the second sub-signal is processed by the phase modulator 240 to obtain the modulated second sub-signal, wherein the format of the modulated second sub-signal includes binary phase shift keying or differential phase shift keying.

[0129] According to embodiments of this disclosure, the transmitter 200 further includes an optical frequency comb 280.

[0130] An optical frequency comb 280 is used to process the initial light source signal to obtain a multi-wavelength light source signal, which is then processed by the second polarization beam splitter 220.

[0131] According to an embodiment of this disclosure, a laser communication system includes: a receiver 100 as described above and a transmitter 200 as described above.

[0132] According to embodiments of this disclosure, the signal light E in the transmitter 200 s Heben Zhenguang E Lo It can be expressed by formulas (1) and (2):

[0133]

[0134]

[0135] Among them, A s ω s , A Lo ω Lo , These represent the amplitude, frequency, and phase of the signal light and the amplitude, frequency, and phase of the local oscillator light, respectively, where j is a coefficient and t is time.

[0136] According to the embodiments of this disclosure, after the mixer 141 in the receiver 100 processes two first sub-signals with different polarization states but the same wavelength, the optical fields E1 and E2 of the output mixed optical signal can be expressed by formulas (3) and (4):

[0137]

[0138]

[0139] According to an embodiment of this disclosure, the balanced detector 142 consists of two photodetectors and a differential circuit. Based on the square law detection principle of the photodetectors, the photocurrents output by the two photodetectors and the differential circuit are I1(t), I2(t), and I(t), respectively.

[0140]

[0141]

[0142]

[0143] Where R is the responsivity of the photodetector, ω IF =ω s -ω Lo This represents the frequency difference between the signal light and the local oscillator light.

[0144] According to embodiments of this disclosure, the local oscillator light and the signal light originate from the same laser 210, therefore ω IF =0, and the current output by the digital signal processor 150 is as shown in formula (8).

[0145]

[0146] According to the embodiments of this disclosure, as can be seen from formula (8), the DC component and noise subtraction after balanced reception are suppressed, and the AC component containing modulation information is retained, so that the transmitted signal can be recovered, thus realizing zero-difference coherent detection based on polarization transmission.

[0147] According to embodiments of this disclosure, by receiving a target optical signal emitted from the transmitter 200, which is obtained by splitting an initial light source signal emitted by the same laser 210, and then combining one of the split optical signals with another split optical signal after phase modulation, the receiver 100 uses a first polarization beam splitter 120 to split the target optical signal into multiple wavelengths for wavelength division processing. This allows for the analysis of the transmission sub-signals in the first sub-signals of each wavelength, ultimately achieving the analysis processing for multi-carrier communication. The high transmission rate of multi-carrier communication, combined with the beam splitting and phase modulation method in the transmitter 200, enables coherent detection of the laser communication system with zero difference, improving the sensitivity of the coherent laser communication system. Simultaneously, the structure of the laser communication system is relatively simple, which helps to reduce the cost of the laser communication system.

[0148] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A coherent laser communication method applied to a receiving end in communication connection with a transmitting end, comprising: receiving a target optical signal transmitted by the transmitting end by using a first telescope, wherein the target optical signal is obtained by splitting an initial optical source signal transmitted by the transmitting end from a same laser, and then performing phase modulation on one of the split optical signals and combining the modulated optical signal with another split optical signal; adjusting a polarization state of the target optical signal by using a polarization controller to avoid crosstalk between X and Y polarization states in the target optical signal, to obtain an adjusted target optical signal; processing the adjusted target optical signal by using a first polarization beam splitter to obtain a first polarization light and a second polarization light; adjusting a polarization state of the first polarization light by using a polarization rotator to obtain an adjusted first polarization light, so that the adjusted first polarization light and the second polarization light have the same polarization state; processing the second polarization light by using an optical amplifier to obtain an amplified second polarization light; for any one of the adjusted first polarization light and the amplified second polarization light, processing the polarization light by using a first optical demultiplexer to obtain a plurality of first demultiplexed signals with different wavelengths; for each two first demultiplexed signals with the same wavelength, processing the two first demultiplexed signals by using a balanced detection device to obtain a transmission sub-signal, wherein a transmission signal comprises a plurality of transmission sub-signals with different wavelengths; processing a plurality of the transmission sub-signals by using a digital signal processor to obtain the transmission signal. 2.The method of claim 1, wherein the balanced detection device comprises a mixer and a balanced detector; and the processing the two first demultiplexed signals by using the balanced detection device to obtain a transmission sub-signal comprises: wherein, processing the two first demultiplexed signals with the same wavelength by using the mixer to obtain a mixed light signal; processing the mixed light signal by using the balanced detector to obtain a target electrical signal representing the transmission sub-signal, so that the digital signal processor processes a plurality of the target electrical signals to obtain the transmission signal. 3.A coherent laser communication method applied to a transmitting end in communication connection with a receiving end, comprising: processing an initial optical source signal generated by a laser by using a second polarization beam splitter to obtain a third polarization light and a fourth polarization light; processing the third polarization light by using a second optical demultiplexer to obtain a plurality of second demultiplexed signals with different wavelengths; for each second demultiplexed signal, processing a transmission sub-signal with the same wavelength and the second demultiplexed signal by using a phase modulator to obtain a modulated second demultiplexed signal; processing a plurality of the modulated second demultiplexed signals by using an optical combiner to obtain an initial optical signal; processing the initial optical signal and the fourth polarization light by using a polarization combiner to obtain a target optical signal. ​ The second telescope is used to emit the target optical signal, so that the receiving end receives the target optical signal by using the first telescope, adjusts the polarization state of the target optical signal by using a polarization controller to avoid crosstalk between X polarization state and Y polarization state in the target optical signal, obtains an adjusted target optical signal, processes the adjusted target optical signal by using a first polarization beam splitter to obtain first polarization light and second polarization light, adjusts the polarization state of the first polarization light by using a polarization rotator to obtain adjusted first polarization light, so that the adjusted first polarization light and the second polarization light have the same polarization state; and processes the second polarization light by using an optical amplifier to obtain amplified second polarization light. For any one of the adjusted first polarization light and the amplified second polarization light, a first optical splitter is used to process the polarization light to obtain a plurality of first sub-signals with different wavelengths; for every two first sub-signals with the same wavelength, a balanced detection device is used to process the two first sub-signals to obtain a transmission sub-signal, wherein a transmission signal includes a plurality of transmission sub-signals with different wavelengths; and a digital signal processor is used to process a plurality of transmission sub-signals to obtain the transmission signal.

4. The method of claim 3, wherein, The processing of the transmission sub-signal with the same wavelength and the second sub-signal by using a phase modulator to obtain a modulated second sub-signal includes: determining a modulation voltage sequence according to the transmission sub-signal; loading the modulation voltage sequence on the phase modulator, and processing the second sub-signal by using the phase modulator to obtain the modulated second sub-signal, wherein the format of the modulated second sub-signal includes binary phase shift keying or differential phase shift keying.

5. The method of claim 3, wherein, Before processing the initial light source signal by using the second polarization beam splitter, the method further includes: processing the initial light source signal by using an optical frequency comb to obtain a multi-wavelength light source signal, and processing the multi-wavelength light source signal by using the second polarization beam splitter.

6. A receiving end of laser communication, the receiving end being in communication connection with a transmitting end, and the receiving end comprising: a first telescope configured to receive a target optical signal transmitted by the transmitting end; a polarization controller configured to adjust a polarization state of the target optical signal to avoid crosstalk between X polarization state and Y polarization state in the target optical signal, and obtain an adjusted target optical signal; a first polarization beam splitter configured to process the adjusted target optical signal to obtain first polarization light and second polarization light; a polarization rotator configured to adjust a polarization state of the first polarization light to obtain adjusted first polarization light, so that the adjusted first polarization light and the second polarization light have the same polarization state; an optical amplifier configured to amplify the second polarization light to obtain amplified second polarization light; a first optical splitter configured to process any one of the adjusted first polarization light and the amplified second polarization light to obtain a plurality of first sub-signals with different wavelengths; a balanced detection device configured to process every two first sub-signals with the same wavelength to obtain a transmission sub-signal, wherein a transmission signal includes a plurality of transmission sub-signals with different wavelengths; and a digital signal processor configured to process a plurality of transmission sub-signals to obtain the transmission signal. A digital signal processor is configured to process the plurality of transmission sub-signals to obtain the transmission signal. 7.A transmitting terminal of laser communication, the transmitting terminal being communicatively connected with a receiving terminal, the transmitting terminal comprising: a laser configured to generate an initial light source signal; a second polarization beam splitter configured to process the initial light source signal to obtain a third polarization light and a fourth polarization light; a second optical wavelength division multiplexer configured to process the third polarization light to obtain a plurality of second sub-signals with different wavelengths; a plurality of phase modulators, each of which is configured to process a transmission sub-signal with a same wavelength and the second sub-signals to obtain a modulated second sub-signal; an optical combiner configured to process the plurality of modulated second sub-signals to obtain an initial light signal; a polarization combiner configured to process the initial light signal and the fourth polarization light to obtain a target light signal; a second telescope configured to transmit the target light signal, so that the receiving terminal receives the target light signal by using a first telescope, adjusts a polarization state of the target light signal by using a polarization controller to avoid crosstalk between an X polarization state and a Y polarization state in the target light signal, obtains an adjusted target light signal, processes the adjusted target light signal by using a first polarization beam splitter to obtain a first polarization light and a second polarization light, adjusts the polarization state of the first polarization light by using a polarization rotator to obtain an adjusted first polarization light, so that the adjusted first polarization light and the second polarization light have a same polarization state, and processes the second polarization light by using an optical amplifier to obtain an amplified second polarization light; for any one of the adjusted first polarization light and the amplified second polarization light, the first optical wavelength division multiplexer is configured to process the polarization light to obtain a plurality of first sub-signals with different wavelengths; for each two first sub-signals with a same wavelength, a balanced detection device is configured to process the two first sub-signals to obtain a transmission sub-signal, wherein a transmission signal comprises a plurality of transmission sub-signals with different wavelengths; and a digital signal processor is configured to process the plurality of transmission sub-signals to obtain the transmission signal. 8.A laser communication system, comprising: the receiving terminal of claim 6; and the transmitting terminal of claim 7.

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