Underwater half-duplex wireless optical communication system and method based on photon counting detection

Abstract

The invention provides an underwater half-duplex wireless optical communication system and method based on photon counting detection, and the system comprises a first communication device and a second communication device, the first communication device is provided with a first communication data interface, and the second communication device is provided with a second communication data interface; the first communication equipment comprises a first processing unit, a first transmitting unit and a first receiving unit; the first receiving unit comprises a first lens, a first single-photon detector and a first low-pass filter; the second communication equipment comprises a second processing unit, a second transmitting unit and a second receiving unit; the second receiving unit comprises a second lens, a second single-photon detector and a second low-pass filter, the system is simple in structure, discrete voltage pulse sequences output by the single-photon detectors are shaped through the low-pass filter, then original information data are recovered through a common data recovery method, the complexity of the system is greatly reduced, and the reliability of the system is improved. And fusion use with a communication system in a traditional detection mode is facilitated.

Description

Technical Field

[0001] The invention relates to the field of underwater wireless communications, and in particular to an underwater half-duplex wireless optical communication system and method based on photon counting detection. Background Art

[0002] The ocean is the cradle of life, covering about 71% of the earth's surface. With the development of social economy, countries are paying more and more attention to the value of the ocean. Marine informatization is an important part of marine development, among which underwater wireless communication is one of the key technologies, which has attracted widespread attention in scientific research, industry, commerce and other fields. Due to the serious attenuation of electromagnetic waves in water, current underwater wireless data transmission mainly relies on underwater acoustic communication. This type of communication uses sound waves as information carriers, and transmits information through sound waves in water, which can achieve a transmission distance of kilometers. However, due to the low frequency of sound waves, the transmission rate of this communication is low, usually in the order of Kbps. Therefore, the current underwater wireless communication system has limitations in large-capacity data transmission.

[0003] In recent years, underwater wireless optical communication, which uses blue-green light from the seawater transmission window as the information carrier and seawater as the transmission medium, has attracted widespread attention in the field of marine engineering due to its outstanding advantage of high transmission rate. At present, underwater wireless optical communication is mainly used to solve the transmission application of short-distance and large-capacity data in engineering. In this process, the distance that the communication equipment can transmit greatly affects the overall performance of the system. An effective way to increase the transmission distance of the communication system is to improve the detection sensitivity of the communication receiving unit. When the optical signal reaching the receiver is relatively weak, the signal can be detected by photon counting detection. This detection method generally uses a single-photon detector to detect the optical signal. Due to its detection sensitivity at the order of photons, it is currently a research hotspot and a potential application mode in this field. However, in the photon counting detection mode, the weak light signal is output in the form of discrete random voltage pulses after photoelectric conversion, which brings difficulties to the recovery of communication data.

[0004] In the related art, a method for extracting the synchronization clock of underwater single-photon communication based on a classification network is disclosed, which provides a basis for data recovery. The algorithm complexity of this method is high, and no technical approach is given for stable transmission of bidirectional data in underwater half-duplex mode (see the patent "A method for extracting synchronization clock of underwater single-photon communication based on a classification network", publication number CN112511234B). In the related art, a photon counting communication method based on a low-pass filter is also disclosed. This method uses a low-pass filter to shape the discrete pulses output by the single-photon detector into a waveform corresponding to the original communication, and then uses a traditional method to recover the original communication data from the waveform. When the power of the optical signal entering the single-photon detector changes, the number of voltage pulses output from the detector will change, which will affect the effectiveness of this method. In this method, there is no way to monitor the number of voltage pulses, and no mechanism for judging whether the working state of the communication system of photon counting detection is stable through the monitoring results. (See the patent "A communication receiving device and system", application number CN202310476111.9). Therefore, for underwater half-duplex wireless optical communication systems, the existing methods do not provide an effective method with simple structure, strong engineering adaptability and communication status monitoring function. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides an underwater half-duplex wireless optical communication system and method based on photon counting detection, which specifically includes:

[0006] In a first aspect, the present invention provides an underwater half-duplex wireless optical communication system based on photon counting detection, comprising:

[0007] A first communication device and a second communication device, wherein the first communication device is provided with a first communication data interface, and the second communication device is provided with a second communication data interface;

[0008] The first communication device includes a first processing unit, a first transmitting unit, and a first receiving unit;

[0009] The first receiving unit includes a first lens, a first single-photon detector, and a first low-pass filter;

[0010] The second communication device includes a second processing unit, a second transmitting unit, and a second receiving unit;

[0011] The second receiving unit includes a second lens, a second single-photon detector, and a second low-pass filter;

[0012] A first processing unit is used to generate a control voltage according to data information input from the first communication data interface, control the first transmitting unit to generate an intensity-modulated first optical signal, the intensity-modulated first optical signal carries first target data information that needs to be transmitted from the first communication device to the second communication device; process the signal from the first receiving unit to recover the second target data information; output the recovered data information through the first communication data interface; count the number of voltage pulse sequences from the first single-photon detector; and control the first transmitting unit to transmit the intensity-modulated first optical signal into the water;

[0013] A first lens is used to converge an intensity-modulated second optical signal from a second communication device into a first single-photon detector, wherein the intensity-modulated second optical signal carries second target data information that needs to be transmitted from the second communication device to the first communication device;

[0014] A first single-photon detector is used to output a second voltage pulse sequence to the first low-pass filter and the first processing unit simultaneously when detecting the intensity-modulated second light signal;

[0015] a first low-pass filter, configured to convert a signal from the first single-photon detector into a second voltage signal, and output the second voltage signal to the first processing unit;

[0016] The second processing unit is used to generate a control voltage according to the data information input from the second communication data interface, control the intensity modulated second optical signal generated by the second transmitting unit; process the signal from the second receiving unit, recover the first target data information therefrom, and output it through the second communication data interface; count the number of voltage pulse sequences from the second single-photon detector; and control the second transmitting unit to transmit the intensity modulated second optical signal into the water;

[0017] a second lens, used for focusing the intensity-modulated first optical signal into a second single-photon detector;

[0018] a second single-photon detector, configured to output a first voltage pulse sequence to a second processing unit and a second low-pass filter simultaneously when detecting the intensity-modulated first light signal;

[0019] The second low-pass filter is used to convert the signal from the second single-photon detector into a first voltage signal, and output the first voltage signal to the second processing unit.

[0020] In a second aspect, the present invention further provides an underwater half-duplex wireless optical communication method based on photon counting detection, which is applied to any underwater half-duplex wireless optical communication system based on photon counting detection as provided in the first aspect, and the method comprises:

[0021] S1, setting the communication parameters in the half-duplex communication mode, the communication parameters including the communication transmission rate, the link switching period, the time length of the first communication device to transmit information to the second communication device within a time period, the time length of the second communication device to transmit information to the first communication device within a time period, and the length of the protection time slot;

[0022] S2, setting the cutoff frequencies of the first low-pass filter and the second low-pass filter, and the optical power ranges of the first receiving unit and the second receiving unit;

[0023] S3, establishing a bidirectional optical communication transmission link between the first communication device and the second communication device based on the communication parameters in the half-duplex communication mode;

[0024] S4, controlling the first processing unit to cache the data information from the first communication data interface to obtain first cached data, or controlling the second processing unit to cache the data information from the second communication data interface to obtain second cached data;

[0025] S5, controlling the first processing unit to divide the first cache data into a plurality of data segments of preset lengths according to a preset time sequence, and performing error correction coding on each data segment according to a preset error correction coding method, to obtain a first data segment, or controlling the second processing unit to divide the second cache data into a plurality of data segments of preset lengths according to a preset time sequence, and performing error correction coding on each data segment according to a preset error correction coding method, to obtain a second data segment;

[0026] S6, based on the communication parameters in the half-duplex communication mode, control the first processing unit to add the first channel monitoring sequence to the end of the first data segment to obtain the first modulation parameter, and use the first modulation parameter to control the first transmitting unit to generate the intensity modulated first optical signal, and send the intensity modulated first optical signal into the water, or control the second processing unit to add the second channel monitoring sequence to the end of the second data segment to obtain the second modulation parameter, and use the second modulation parameter to control the second transmitting unit to generate the intensity modulated second optical signal, and send the intensity modulated second optical signal into the water;

[0027] S7, based on the communication parameters in the half-duplex communication mode, control the first single-photon detector to convert the intensity-modulated second optical signal into a second voltage pulse sequence, and simultaneously output the second voltage pulse sequence to the first processing unit and the first low-pass filter, control the first low-pass filter to filter the second voltage pulse sequence to obtain a second voltage signal, and output the second voltage signal to the first processing unit, or control the second single-photon detector to convert the intensity-modulated first optical signal into a first voltage pulse sequence, and simultaneously output the first voltage pulse sequence to the second processing unit and the second low-pass filter, control the second low-pass filter to filter the first voltage pulse sequence to obtain a first voltage signal, and output the first voltage signal to the second processing unit;

[0028] S8, based on the communication parameters in the half-duplex communication mode, controls the first processing unit to recover the second target data information according to the second voltage signal, and outputs the second target data information through the first communication data interface, and judges the working state of the first communication device according to the second voltage signal, the second voltage pulse sequence and the optical power range of the first receiving unit; or controls the second processing unit to recover the first target data information according to the first voltage signal, and outputs the first target data information through the second communication data interface, and judges the working state of the second communication device according to the first voltage signal, the first voltage pulse sequence and the optical power range of the second receiving unit.

[0029] Beneficial effects of the present invention:

[0030] The underwater half-duplex wireless optical communication system based on photon counting detection provided by the present invention comprises a first communication device and a second communication device, wherein the first communication device is provided with a first communication data interface, and the second communication device is provided with a second communication data interface; the first communication device comprises a first processing unit, a first transmitting unit, and a first receiving unit; the first receiving unit comprises a first lens, a first single-photon detector, and a first low-pass filter; the second communication device comprises a second processing unit, a second transmitting unit, and a second receiving unit; the second receiving unit comprises a second lens, a second single-photon detector, and a second low-pass filter. The system has a simple structure, and a low-pass filter is used to shape the discrete voltage pulse sequence output by the single-photon detector, and then a commonly used data recovery method is used to restore the original information data, which greatly reduces the complexity of the system and facilitates the integration with the communication system of the traditional detection mode. At the same time, during the communication process, when the first communication device and the second communication device form a modulation parameter to generate an optical signal, a first channel monitoring sequence and a second channel monitoring sequence are added to the modulation parameter. Based on the sequence, the two communication devices can monitor the power of the optical signal entering the receiver, and then evaluate and monitor the state of the communication system based on photon counting detection. In addition, the present invention adopts a half-duplex bidirectional communication mode, which is one of the common wireless optical communication technology systems underwater. Therefore, the method provided by the present invention is convenient for rapid engineering application.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the architecture of an underwater half-duplex wireless optical communication system based on photon counting detection provided by the present invention;

[0033] Figure 2 A schematic diagram of a flow chart of an underwater half-duplex wireless optical communication method based on photon counting detection provided by the present invention;

[0034] Figure 3 A schematic diagram of an experimental system provided by the present invention;

[0035] Figure 4 A schematic diagram of data transmission in one cycle in a half-duplex communication mode provided by the present invention;

[0036] Figure 5 A schematic diagram of a simulation result provided by the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0038] Figure 1The schematic diagram of the architecture of an underwater half-duplex wireless optical communication system based on photon counting detection provided by the present invention is as follows: Figure 1 As shown, the system includes:

[0039] The first communication device and the second communication device are provided with a first communication data interface, and the second communication device is provided with a second communication data interface.

[0040] The first communication device includes a first processing unit, a first transmitting unit, and a first receiving unit.

[0041] The first receiving unit includes a first lens, a first single-photon detector, and a first low-pass filter.

[0042] The second communication device includes a second processing unit, a second transmitting unit, and a second receiving unit.

[0043] The second receiving unit includes a second lens, a second single-photon detector, and a second low-pass filter.

[0044] Among them, the first processing unit is used to generate a control voltage according to the data information input from the first communication data interface, control the first transmitting unit to generate an intensity-modulated first optical signal, and the intensity-modulated first optical signal carries the first target data information that needs to be transmitted from the first communication device to the second communication device; process the signal from the first receiving unit to recover the second target data information therefrom; output the recovered data information through the first communication data interface; count the number of voltage pulse sequences from the first single-photon detector; and control the first transmitting unit to emit the intensity-modulated first optical signal into the water.

[0045] The first lens is used to converge the intensity-modulated second optical signal from the second communication device into the first single-photon detector, wherein the intensity-modulated second optical signal carries second target data information that needs to be transmitted from the second communication device to the first communication device.

[0046] The first single-photon detector is used to output a second voltage pulse sequence to the first low-pass filter and the first processing unit simultaneously when detecting the intensity-modulated second light signal.

[0047] The first low-pass filter is used to convert the signal from the first single-photon detector into a second voltage signal, and output the second voltage signal to the first processing unit.

[0048] It can be understood that the second voltage signal carries second target data information from the second communication device.

[0049] The second processing unit is used to generate a control voltage according to the data information input from the second communication data interface, control the intensity modulated second optical signal generated by the second transmitting unit; process the signal from the second receiving unit, recover the first target data information therefrom, and output it through the second communication data interface; count the number of voltage pulse sequences from the second single-photon detector; and control the second transmitting unit to transmit the intensity modulated second optical signal into the water.

[0050] The second lens is used to converge the intensity-modulated first light signal into the second single-photon detector.

[0051] The second single-photon detector is used to output a first voltage pulse sequence to the second processing unit and the second low-pass filter simultaneously when detecting the intensity-modulated first light signal.

[0052] The second low-pass filter is used to convert the signal from the second single-photon detector into a first voltage signal, and output the first voltage signal to the second processing unit.

[0053] It can be understood that the second voltage signal carries the first target data information from the first communication device.

[0054] Optionally, the first communication device and the second communication device use light waves in the blue-green band as information carriers and perform bidirectional data transmission through a half-duplex communication mode.

[0055] Optionally, the first emitting unit and the second emitting unit are both composed of light sources in the blue-green band.

[0056] Optionally, the voltage pulse sequences output by the first single-photon detector and the second single-photon detector are discrete narrow pulses.

[0057] Optionally, the first processing unit is specifically used to cache data information from the first communication data interface to obtain first cached data; divide the first cached data into multiple data segments of preset lengths according to a preset time sequence, and perform error correction coding on each data segment according to a preset error correction coding method to obtain a first data segment; add a first channel monitoring sequence to the back end of the first data segment to obtain a first modulation parameter, and use the first modulation parameter to control the first transmitting unit to generate an intensity-modulated first optical signal.

[0058] The second processing unit is specifically used to cache the data information from the second communication data interface to obtain second cached data; divide the second cached data into multiple data segments of preset length according to a preset time sequence, and perform error correction coding on each data segment according to a preset error correction coding method to obtain a second data segment; add a second channel monitoring sequence to the back end of the second data segment to obtain a second modulation parameter, and use the second modulation parameter to control the second transmitting unit to generate an intensity-modulated second optical signal.

[0059] Through this method, the first intensity modulated optical signal and the second intensity modulated optical signal both include monitoring coding information for monitoring the corresponding transmission channels, laying a foundation for subsequently using a preset channel monitoring sequence to monitor the status of equipment in the communication system.

[0060] Optionally, the first processing unit is specifically used to recover the second target data information based on the second voltage signal, and output the second target data information through the first communication data interface, and judge the working status of the first communication device based on the second voltage signal, the second voltage pulse sequence and the optical power range of the first receiving unit.

[0061] The second processing unit is specifically used to recover the first target data information according to the first voltage signal, output the first target data information through the second communication data interface, and judge the working state of the second communication device according to the first voltage signal, the first voltage pulse sequence and the optical power range of the second receiving unit.

[0062] The present invention uses a preset channel monitoring sequence to monitor the status of the equipment in the communication system. During use, these monitoring information can be provided to the application platform, which is convenient for the application platform to control the system status and also convenient for the application platform to integrate this half-duplex communication system based on photon counting detection with the communication system based on traditional detection.

[0063] The underwater half-duplex wireless optical communication system based on photon counting detection provided by the present invention comprises a first communication device and a second communication device, wherein the first communication device is provided with a first communication data interface, and the second communication device is provided with a second communication data interface; the first communication device comprises a first processing unit, a first transmitting unit, and a first receiving unit; the first receiving unit comprises a first lens, a first single-photon detector, and a first low-pass filter; the second communication device comprises a second processing unit, a second transmitting unit, and a second receiving unit; the second receiving unit comprises a second lens, a second single-photon detector, and a second low-pass filter; the first processing unit is used to generate a control voltage according to data information input from the first communication data interface to control the first transmitting unit Generate an intensity-modulated first optical signal, the intensity-modulated first optical signal carries first target data information that needs to be transmitted from the first communication device to the second communication device; process the signal from the first receiving unit to recover the second target data information; output the recovered data information through the first communication data interface; count the number of voltage pulse sequences from the first single-photon detector; control the first transmitting unit to transmit the intensity-modulated first optical signal into the water; a first lens is used to converge the intensity-modulated second optical signal from the second communication device to the first single-photon detector, the intensity-modulated second optical signal carries the second target data information that needs to be transmitted from the second communication device to the first communication device; the first single-photon detector The detector is used to output a second voltage pulse sequence to the first low-pass filter and the first processing unit simultaneously when detecting the intensity-modulated second light signal; the first low-pass filter is used to convert the signal from the first single-photon detector into a second voltage signal, and output the second voltage signal to the first processing unit; the second processing unit is used to generate a control voltage according to the data information input from the second communication data interface, and control the intensity-modulated second light signal generated by the second transmitting unit; process the signal from the second receiving unit, recover the first target data information therefrom, and output it through the second communication data interface; count the number of the voltage pulse sequence from the second single-photon detector; control the second transmitting unit to emit the intensity-modulated second light signal into the water a second light signal modulated by the intensity modulated light; a second lens, used to converge the first light signal modulated by the intensity into the second single-photon detector; the second single-photon detector, used to output a first voltage pulse sequence to the second processing unit and the second low-pass filter at the same time when detecting the first light signal modulated by the intensity; the second low-pass filter is used to convert the signal from the second single-photon detector into a first voltage signal, and output the first voltage signal to the second processing unit. The system uses a low-pass filter to shape the discrete voltage pulse sequence output by the single-photon detector, and then uses the data recovery method commonly used in ordinary detection systems to restore the original information data, which greatly reduces the complexity of the system and is also convenient for integration with communication systems with traditional detection modes.At the same time, during the communication process, when the first communication device and the second communication device form modulation parameters to generate optical signals, the first channel monitoring sequence and the second channel monitoring sequence are added to the modulation parameters. Based on the sequence, the two communication devices can monitor the power of the optical signal entering the receiver, and then evaluate and monitor the state of the communication system based on photon counting detection. In addition, the present invention adopts a bidirectional communication mode of a half-duplex system, which is one of the common wireless optical communication technology systems underwater. Therefore, the method provided by the present invention is convenient for rapid engineering application.

[0064] Figure 2 A flow chart of an underwater half-duplex wireless optical communication method based on photon counting detection provided by the present invention is provided. The method can be applied to any underwater half-duplex wireless optical communication system based on photon counting detection provided by the above embodiments.

[0065] like Figure 2 As shown, the method includes:

[0066] S1. Set the communication parameters in half-duplex communication mode.

[0067] Among them, the communication parameters include: communication transmission rate, link switching period, time length for the first communication device to transmit information to the second communication device within a time period, time length for the second communication device to transmit information to the first communication device within a time period, and protection time slot length.

[0068] S2. Set the cutoff frequencies of the first low-pass filter and the second low-pass filter, and the optical power ranges of the first receiving unit and the second receiving unit.

[0069] It is assumed that the target low-pass filter is the first low-pass filter or the second low-pass filter.

[0070] In a possible implementation, for a target low-pass filter, setting a cutoff frequency of the target low-pass filter includes the following steps A1-A:

[0071] A1. Generate a pseudo-random binary sequence using a bit error meter according to the communication transmission rate in the half-duplex communication mode. Based on the pseudo-random binary sequence, control the transmitting unit corresponding to the optical signal received by the device where the target low-pass filter is located to generate an intensity-modulated optical signal.

[0072] Specifically, when the target low-pass filter is the first low-pass filter, based on the pseudo-random binary sequence, control Figure 1 The second transmitting unit in the second communication device in the underwater half-duplex wireless optical communication system based on photon counting detection generates an intensity modulated second optical signal; when the target low-pass filter is the second low-pass filter, based on a pseudo-random binary sequence, controls Figure 1The first transmitting unit in the first communication device in the underwater half-duplex wireless optical communication system based on photon counting detection generates an intensity-modulated first optical signal.

[0073] A2. The intensity modulated optical signal generated is attenuated by an adjustable optical attenuator, and the attenuated optical signal is incident on a single-photon detector in a device where a target low-pass filter is located, so that the single-photon detector generates a discrete voltage pulse sequence.

[0074] Specifically, when the target low-pass filter is the first low-pass filter, the intensity-modulated second optical signal generated is attenuated by an adjustable optical attenuator, and the attenuated optical signal is incident on the first single-photon detector, so that the first single-photon detector generates a discrete second voltage pulse sequence; when the target low-pass filter is the second low-pass filter, the intensity-modulated first optical signal generated is attenuated by an adjustable optical attenuator, and the attenuated optical signal is incident on the second single-photon detector, so that the second single-photon detector generates a discrete first voltage pulse sequence.

[0075] A3. Input the voltage pulse sequence to the target low-pass filter, and input the voltage signal after passing through the target low-pass filter to the bit error tester to test the bit error rate.

[0076] Specifically, when the target low-pass filter is the first low-pass filter, the second voltage pulse sequence is input into the first low-pass filter, and the second voltage signal after passing through the first low-pass filter is input into the bit error meter to test the bit error rate; when the target low-pass filter is the second low-pass filter, the first voltage pulse sequence is input into the second low-pass filter, and the first voltage signal after passing through the second low-pass filter is input into the bit error meter to test the bit error rate.

[0077] A4. Adjust the cutoff frequency of the target low-pass filter so that the measured bit error rate is lower than a preset threshold value, thereby completing the cutoff frequency setting of the target low-pass filter.

[0078] Specifically, when the target low-pass filter is the first low-pass filter, the cutoff frequency of the first low-pass filter is adjusted so that the measured bit error rate is lower than the preset threshold value, and the cutoff frequency at this time is the required cutoff frequency of the first low-pass filter; when the target low-pass filter is the second low-pass filter, the cutoff frequency of the second low-pass filter is adjusted so that the measured bit error rate is lower than the preset threshold value, and the cutoff frequency at this time is the required cutoff frequency of the second low-pass filter.

[0079] Further, in a possible implementation, for a target receiving unit, setting an optical power range of the target receiving unit includes the following steps B1 and B2:

[0080] B1. After setting the cutoff frequency of the low-pass filter in the device where the target receiving unit is located, use an adjustable optical attenuator to increase the optical power of the single-photon detector entering the target receiving unit until the measured bit error rate is lower than the preset threshold, use an arbitrary waveform generator to generate a periodic square wave, and use the generated square wave to control the transmitting unit corresponding to the optical signal received by the target receiving unit to generate an intensity-modulated optical signal, record the number of average voltage pulse sequences output by the single-photon detector in the target receiving unit in each cycle, and use the number of average voltage pulse sequences in each cycle to represent the maximum optical power of the target receiving unit.

[0081] B2. Use an adjustable optical attenuator to reduce the optical power of the single-photon detector entering the target receiving unit until the measured bit error rate is lower than a preset threshold value, use an arbitrary waveform generator to generate a periodic square wave, and use the generated square wave to control the transmitting unit corresponding to the optical signal received by the target receiving unit to generate an intensity-modulated optical signal, record the average number of voltage pulse sequences output by the single-photon detector in the target receiving unit in each cycle, and use the average number of voltage pulse sequences in each cycle to represent the minimum optical power of the target receiving unit.

[0082] Specifically, in the above B1 and B2, the generated square wave is used to control the transmitting unit in the device corresponding to the optical signal detected by the target receiving unit to generate an intensity modulated optical signal, which means that when the target receiving unit is the first receiving unit, the second transmitting unit is controlled to generate an optical signal; when the target receiving unit is the second receiving unit, the first transmitting unit is controlled to generate an optical signal.

[0083] Optionally, the frequencies of the periodic square waves in B1 and B2 are equal, and the magnitude of the frequency is equal to half of the magnitude of the communication transmission rate.

[0084] S3. Establish a bidirectional optical communication transmission link between the first communication device and the second communication device based on preset communication parameters in the half-duplex communication mode.

[0085] Optionally, S3 includes: setting the first communication device and the second communication device as the master device and the slave device, respectively; controlling the master device to transmit a link establishment signal to the slave device with a preset link switching period, controlling the slave device to send a response signal to the master device after receiving the link establishment signal, and controlling the master device to transmit a link establishment signal to the slave device again when detecting the response signal, and repeating this process until the master device and the slave device receive N consecutive response signals and N link establishment signals, respectively, thereby completing the establishment of a two-way communication link.

[0086] Wherein, N is a positive integer greater than or equal to 1.

[0087] It should be noted that the second communication device may also be set as a master device and the first communication device may be set as a slave device, and there is no limitation to this.

[0088] S4. Control the first processing unit to cache the data information from the first communication data interface to obtain first cache data, or control the second processing unit to cache the data information from the second communication data interface to obtain second cache data.

[0089] S5. Control the first processing unit to divide the first cache data into multiple data segments of preset lengths according to a preset time sequence, and perform error correction coding on each data segment according to a preset error correction coding method to obtain a first data segment, or control the second processing unit to divide the second cache data into multiple data segments of preset lengths according to a preset time sequence, and perform error correction coding on each data segment according to a preset error correction coding method to obtain a second data segment.

[0090] S6. Based on the communication parameters in the half-duplex communication mode, control the first processing unit to add the first channel monitoring sequence to the end of the first data segment to obtain the first modulation parameter, and use the first modulation parameter to control the first transmitting unit to generate an intensity modulated first optical signal, and send the intensity modulated first optical signal into the water, or control the second processing unit to add the second channel monitoring sequence to the end of the second data segment to obtain the second modulation parameter, and use the second modulation parameter to control the second transmitting unit to generate an intensity modulated second optical signal, and send the intensity modulated second optical signal into the water.

[0091] Optionally, the sum of the time lengths of the first data segment and the first channel monitoring sequence is not greater than the time length for the first communication device to transmit information to the second communication device within a time period; the sum of the time lengths of the second data segment and the second channel monitoring sequence is not greater than the time length for the second communication device to transmit information to the first communication device within a time period.

[0092] Optionally, the first channel monitoring sequence and the second channel monitoring sequence are square wave sequences, and the period is the same as the periodic square wave frequency in steps B1 and B2.

[0093] S7. Based on the communication parameters in the half-duplex communication mode, control the first single-photon detector to convert the intensity-modulated second light signal into a second voltage pulse sequence, and simultaneously output the second voltage pulse sequence to the first processing unit and the first low-pass filter, control the first low-pass filter to filter the second voltage pulse sequence to obtain a second voltage signal, and output the second voltage signal to the first processing unit; or control the second single-photon detector to convert the intensity-modulated first light signal into a first voltage pulse sequence, and simultaneously output the first voltage pulse sequence to the second processing unit and the second low-pass filter, control the second low-pass filter to filter the first voltage pulse sequence to obtain a first voltage signal, and output the first voltage signal to the second processing unit.

[0094] S8. Based on the communication parameters in the half-duplex communication mode, control the first processing unit to recover the second target data information according to the second voltage signal, and output the second target data information through the first communication data interface, and judge the working state of the first communication device according to the second voltage signal, the second voltage pulse sequence and the optical power range of the first receiving unit; or control the second processing unit to recover the first target data information according to the first voltage signal, and output the first target data information through the second communication data interface, and judge the working state of the second communication device according to the first voltage signal, the first voltage pulse sequence and the optical power range of the second receiving unit.

[0095] Optionally, step S8 includes: controlling the first processing unit to recover the second data segment and the second channel monitoring sequence from the second voltage signal according to a combination of the second channel monitoring sequence and the second data segment; controlling the first processing unit to perform error correction decoding according to the second data segment and a preset error correction coding method to obtain second target data information, and output the second target data information through the first communication data interface; controlling the first processing unit to search for the total number of second voltage pulse sequences in the corresponding time period according to the second channel monitoring sequence, and obtain the number of voltage pulse sequences in each cycle in combination with the number of cycles of the periodic square wave corresponding to the second channel monitoring sequence, and compare the obtained number of voltage pulse sequences in each cycle with the maximum optical power and minimum optical power values ​​of the first receiving unit, and use the comparison result as the working status parameter of the first communication device.

[0096] Specifically, when the number of voltage pulse sequences in each cycle is between the maximum optical power and the minimum optical power of the first receiving unit, it indicates that the working state of the first communication device is good; otherwise, it indicates that the working state of the first communication device is abnormal, wherein, when the number of voltage pulse sequences in each cycle is greater than the maximum optical power of the first receiving unit, it indicates that the optical signal power detected by the first receiving unit is too high, and when the number of voltage pulse sequences in each cycle is less than the minimum optical power of the first receiving unit, it indicates that the optical signal power detected by the first receiving unit is too low.

[0097] Optionally, step S8 includes: controlling the second processing unit to recover the first data segment and the first channel monitoring sequence from the first voltage signal according to a combination of the first channel monitoring sequence and the first data segment; controlling the second processing unit to perform error correction decoding according to the first data segment and a preset error correction coding method to obtain first target data information, and output the first target data information through the second communication data interface; controlling the second processing unit to search for the total number of first voltage pulse sequences in the corresponding time period according to the first channel monitoring sequence, and obtain the number of voltage pulse sequences in each cycle in combination with the number of cycles of the periodic square wave corresponding to the first channel monitoring sequence, and compare the obtained number of voltage pulse sequences in each cycle with the maximum optical power and minimum optical power values ​​of the second receiving unit, and use the comparison result as the working status parameter of the second communication device.

[0098] Specifically, when the number of voltage pulse sequences in each cycle is between the maximum optical power and the minimum optical power of the second receiving unit, it indicates that the working state of the second communication device is good; otherwise, it indicates that the working state of the second communication device is abnormal, wherein, when the number of voltage pulse sequences in each cycle is greater than the maximum optical power of the second receiving unit, it indicates that the optical signal power detected by the second receiving unit is too high, and when the number of voltage pulse sequences in each cycle is less than the minimum optical power of the second receiving unit, it indicates that the optical signal power detected by the second receiving unit is too low.

[0099] As for the method embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the specific contents and beneficial effects and other related matters can be referred to the partial description of the system embodiment.

[0100] In order to verify the effectiveness of the embodiments of the present invention, the present invention also provides a set of simulation experiments, such as Figure 3 As shown, the verification system consists of a first communication device, a second communication device, a water tank, a first computer, a second computer, a first variable attenuator, and a second variable attenuator.

[0101] The water tank is 2 meters long and is used to simulate a water environment. The first optical signal and the second optical signal are transmitted through the water in the water tank. Both the first optical signal and the second optical signal are intensity modulated optical signals, and the modulation format is On-Off Keying (OOK).

[0102] The first variable attenuator and the second variable attenuator are used to change the power of the second optical signal reaching the first communication device and the power of the first optical signal reaching the second communication device, respectively, so that the single photon detectors in the two communication devices can output discrete voltage pulses.

[0103] The first computer is connected to the first communication device through the first communication data interface using the TCP / IP protocol; the second computer is connected to the second communication device through the second communication data interface using the TCP / IP protocol; the two computers can transmit and receive two-way data with each other through the underwater half-duplex wireless optical communication system.

[0104] The first communication device is composed of a first transmitting unit, a first receiving unit, and a first processing unit. The first transmitting unit is composed of a light emitting diode (LED) with a central wavelength of 470nm and a spectral width of 30nm, and emits an intensity-modulated first optical signal into the water under the control of the first processing unit. The first optical signal carries data information that needs to be transmitted from the first communication device to the second communication device; the first receiving unit is composed of a first lens, a first single-photon detector, and a first low-pass filter. Among them, the first lens is used to converge the second optical signal from the second communication device into the first single-photon detector, and the second optical signal carries data information sent from the second communication device; the first single-photon detector adopts a Geiger mode avalanche photodiode (APD) with a counting rate of 40Mcps. When a weak second optical signal is detected, a pulse sequence in the form of an output voltage is simultaneously given to the first low-pass filter and the first processing unit; the first low-pass filter converts the signal from the first single-photon detector into a voltage signal carrying data information from the second communication device, and outputs it to the first processing unit; the first processing unit generates a control voltage according to the data information input by the first communication data interface, modulates the first transmitting unit to generate a first optical signal, and processes the signal from the first receiving unit, recovers the data information sent by the second communication device, and outputs it through the first communication data interface; the first processing unit can count the number of voltage pulses from the first single-photon detector.

[0105] The second communication device is composed of a second transmitting unit, a second receiving unit, and a second processing unit. The second transmitting unit is composed of an LED with a central wavelength of 470nm and a spectrum width of 30nm. Under the control of the second processing unit, the second optical signal modulated in intensity is emitted into the water. The second optical signal carries data information that needs to be transmitted from the second communication device to the first communication device. The second receiving unit is composed of a second lens, a second single-photon detector, and a second low-pass filter. Among them, the second lens is used to converge the first optical signal from the first communication device to the second single-photon detector, and the first optical signal carries data information sent from the first communication device; the second single-photon detector adopts a Geiger mode avalanche photodiode with a counting rate of 40Mcps. When a weak first optical signal is detected, a pulse sequence in the form of an output voltage is simultaneously given to the second processing unit and the second low-pass filter; the second low-pass filter converts the signal from the second single-photon detector into a voltage signal carrying data information from the first communication device, and outputs it to the second processing unit; the second processing unit generates a control voltage according to the data information input by the second communication data interface, modulates the second transmitting unit to generate a second optical signal, and processes the signal from the second receiving unit, recovers the data information sent by the first communication device, and outputs it through the second communication data interface; the second processing unit can count the number of voltage pulses from the second single-photon detector.

[0106] Among them, half-duplex communication mode is as follows Figure 4 As shown, the information transmission of the two communication devices is periodically time-divided. When the first optical signal is sent from the first communication device to the second communication device, the first processing unit controls the first transmitting unit to generate the first optical signal and does not receive the voltage signal from the first receiving unit; the second processing unit receives the voltage signal from the second receiving unit and controls the second transmitting unit not to transmit the second optical signal. When the second optical signal is sent from the second communication device to the first communication device, the second processing unit controls the second transmitting unit to generate the second optical signal and does not receive the voltage signal from the second receiving unit, the first processing unit receives the voltage signal from the first receiving unit and controls the first transmitting unit not to transmit the first optical signal; when the above two working modes are switched, a certain amount of free time is reserved as a protection time slot, at which time the first processing unit controls the first transmitting unit not to generate the first optical signal and does not receive the voltage signal from the first receiving unit, and the second processing unit controls the second transmitting unit not to generate the second optical signal and does not receive the voltage signal from the second receiving unit.

[0107] The counting rate of the first single photon detector and the second single photon detector are both 40Mcps, the output voltage pulse amplitude is 1.8V, and the pulse width is 25ns. The first processing unit and the second processing unit are circuit boards made based on Xilinx's Zynq7020.

[0108] Before working, the communication transmission rate is preset to 2Mbps, the link switching period of the half-duplex communication device is 100ms, the time length of the first communication device transmitting information to the second communication device within a time period is 50ms, the time length of the second communication device transmitting information to the first communication device within a time period is 50ms, and the protection time slot length is 0. The communication system uses OOK modulation to control the LED to generate optical signals.

[0109] According to the preset 2Mbps transmission rate, a PRBS code is generated at a rate of 2Mbps using a bit error meter, and the LED is driven to emit light. According to the above step S2, the cutoff frequencies of the first low-pass filter and the second low-pass filter finally selected are both 2MHz.

[0110] According to the preset 2Mbps transmission rate, the bit error rate is 3.8×10 -3 To preset the threshold, a square wave signal of 1000 cycles of 1 MHz is generated by using an arbitrary waveform generator, and the LED is driven to emit light. According to the above step S2, it is determined that when the number of voltage pulses output by the first single-photon detector in one cycle is between 10 and 18, the system's bit error rate is less than the preset threshold. 10 voltage pulses and 18 voltage pulses are used to mark the minimum optical power and maximum optical power for the system to work normally, respectively.

[0111] The first communication device is preset as the master device and the second communication device is preset as the slave device. The master device transmits a link establishment signal to the slave device with a preset link switching period. After receiving the link establishment signal, the slave device sends a response signal. When the master device detects the response signal, it continues to send the response signal, and repeats this process. When the two devices receive the preset response signal and link establishment signal five times in succession, it indicates that a two-way communication link has been established between the two communication devices, and the two devices work according to the preset communication transmission rate, the link switching period of the half-duplex communication device, the length of time for the first communication device to transmit information to the second communication device within a time period, the length of time for the second communication device to transmit information to the first communication device within a time period, the length of the protection time slot and other parameters.

[0112] The first processing unit in the first communication device caches the data information from the first communication data interface to obtain first cached data; the second processing unit in the second communication device caches the data information from the second communication data interface to obtain second cached data.

[0113] The first processing unit in the first communication device divides the first cache data into multiple data segments with preset lengths according to a preset time sequence, and performs error correction coding on each data segment according to a preset Reed-Solomon code (RS) coding to obtain a first data segment; the second processing unit in the second communication device divides the second cache data of S4 into multiple data segments with preset lengths according to a preset time sequence, and performs error correction coding on each data segment according to a preset RS error correction coding method to obtain a second data segment; the length of the first data segment and the second data segment does not exceed 40ms.

[0114] In the half-duplex communication mode, the first processing unit in the first communication device adds a square wave with a period of 1MHz and a length of 10ms to the back end of the first data segment as a first channel monitoring sequence, and uses it to modulate the first transmitting unit to generate an intensity-modulated first optical signal, and sends it into the water; the second processing unit in the second communication device adds a square wave with a period of 1MHz and a length of 10ms to the back end of the second data segment as a second channel monitoring sequence, and uses it to modulate the second transmitting unit to generate an intensity-modulated second optical signal, and sends it into the water.

[0115] like Figure 5 As shown, the first single-photon detector in the first receiving unit in the first communication device converts the second light signal into a second voltage pulse sequence, and simultaneously outputs it to the first processing unit and the first low-pass filter in the first receiving unit, and the second voltage signal passing through the first low-pass filter is also output to the first processing unit; the second single-photon detector in the second receiving unit in the second communication device converts the first light signal into a first voltage pulse sequence, and simultaneously outputs it to the second processing unit and the second low-pass filter in the second receiving unit, and the first voltage signal passing through the second low-pass filter is also output to the second processing unit.

[0116] The first processing unit recovers and distinguishes the second data segment and the second channel monitoring sequence based on the second voltage signal and the combination of the second channel monitoring sequence and the second data segment of S6; the second processing unit recovers and distinguishes the first data segment and the first channel monitoring sequence based on the first voltage signal and the combination of the first channel monitoring sequence and the first data segment of S6.

[0117] The first processing unit performs error correction decoding based on the second data segment in combination with a preset error correction coding method to obtain original data information from the second communication device, and outputs it through the first communication data interface; the second processing unit performs error correction decoding based on the first data segment in combination with a preset error correction coding method to obtain original data information from the first communication device, and outputs it through the second communication data interface.

[0118] The first processing unit searches for the total number of the second voltage pulse sequence in the corresponding time period according to the second channel monitoring sequence, and obtains the number of voltage pulses in each period in combination with the number of periods of the periodic square wave corresponding to the second channel monitoring sequence, and compares the number with the marked values ​​of the maximum optical power and the minimum optical power, and uses the result as the working status parameter of the first communication device; the second processing unit searches for the total number of the first voltage pulse sequence in the corresponding time period according to the first channel monitoring sequence, and obtains the number of voltage pulses in each period in combination with the number of periods of the periodic square wave corresponding to the first channel monitoring sequence, and compares the number with the marked values ​​of the maximum optical power and the minimum optical power, and uses the result as the working status parameter of the second communication device.

[0119] The above system is used to build a file transfer system based on the File Transfer Protocol (FTP) between the first computer and the second computer, and a two-way data transmission service is established using the first communication device and the second communication device. This is a two-way communication transmission protocol. A 5MB file is transferred from the first computer to the second computer 6 times, and the results are shown in Table 1. During this process, the working status parameters detected by the first communication device and the second communication device.

[0120] This experiment verifies the effectiveness of the present invention.

[0121] Table 1 File transfer experimental results

[0122] Experiment No. 1 2 3 4 5 6 Transmission time(s) 144 144 144 186 144 162

[0123] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0124] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. An underwater half-duplex wireless optical communication system based on photon counting detection, characterized in that: include: A first communication device and a second communication device, wherein the first communication device is provided with a first communication data interface, and the second communication device is provided with a second communication data interface; The first communication device includes a first processing unit, a first transmitting unit, and a first receiving unit; The first receiving unit includes a first lens, a first single-photon detector, and a first low-pass filter; The second communication device includes a second processing unit, a second transmitting unit, and a second receiving unit; The second receiving unit includes a second lens, a second single-photon detector, and a second low-pass filter; The first processing unit is used to generate a control voltage according to the data information input from the first communication data interface, control the first transmitting unit to generate an intensity-modulated first optical signal, wherein the intensity-modulated first optical signal carries first target data information that needs to be transmitted from the first communication device to the second communication device; process the signal from the first receiving unit to recover the second target data information; output the recovered data information through the first communication data interface; count the number of voltage pulse sequences from the first single-photon detector; and control the first transmitting unit to transmit the intensity-modulated first optical signal into water; The first lens is used to converge the intensity-modulated second optical signal from the second communication device into the first single-photon detector, wherein the intensity-modulated second optical signal carries second target data information that needs to be transmitted from the second communication device to the first communication device; The first single-photon detector is used to output a second voltage pulse sequence to the first low-pass filter and the first processing unit simultaneously when detecting the intensity-modulated second light signal; The first low-pass filter is used to convert the signal from the first single-photon detector into a second voltage signal, and output the second voltage signal to the first processing unit; The second processing unit is used to generate a control voltage according to the data information input from the second communication data interface, control the intensity modulated second optical signal generated by the second transmitting unit; process the signal from the second receiving unit, recover the first target data information therefrom, and output it through the second communication data interface; count the number of voltage pulse sequences from the second single-photon detector; control the second transmitting unit to transmit the intensity modulated second optical signal into the water; The second lens is used to converge the intensity-modulated first optical signal into the second single-photon detector; The second single-photon detector is used to output a first voltage pulse sequence to the second processing unit and the second low-pass filter simultaneously when detecting the intensity-modulated first light signal; The second low-pass filter is used to convert the signal from the second single-photon detector into a first voltage signal, and output the first voltage signal to the second processing unit.

2. The system according to claim 1, characterized in that The first processing unit is specifically configured to cache data information from the first communication data interface to obtain first cache data; divide the first cache data into a plurality of data segments of preset lengths according to a preset time sequence, and perform error correction coding on each data segment according to a preset error correction coding method to obtain a first data segment; add a first channel monitoring sequence to the rear end of the first data segment to obtain a first modulation parameter, and use the first modulation parameter to control the first transmitting unit to generate an intensity modulated first optical signal; The second processing unit is specifically used to cache data information from the second communication data interface to obtain second cache data; divide the second cache data into multiple data segments of preset lengths according to a preset time sequence, and perform error correction coding on each data segment according to the preset error correction coding method to obtain a second data segment; add a second channel monitoring sequence to the back end of the second data segment to obtain a second modulation parameter, and use the second modulation parameter to control the second transmitting unit to generate an intensity-modulated second optical signal.

3. The system according to claim 2, characterized in that The first processing unit is specifically used to recover the second target data information according to the second voltage signal, output the second target data information through the first communication data interface, and judge the working state of the first communication device according to the second voltage signal, the second voltage pulse sequence and the optical power range of the first receiving unit; The second processing unit is specifically used to recover the first target data information based on the first voltage signal, and output the first target data information through the second communication data interface, and judge the working status of the second communication device based on the first voltage signal, the first voltage pulse sequence and the optical power range of the second receiving unit.

4. The system according to claim 3, characterized in that The first emitting unit and the second emitting unit are both composed of light sources in the blue-green band.

5. An underwater half-duplex wireless optical communication method based on photon counting detection, characterized in that: Applied to any underwater half-duplex wireless optical communication system based on photon counting detection as provided in claims 1-4, the method comprising: S1, setting communication parameters in half-duplex communication mode, the communication parameters including communication transmission rate, link switching period, time length of the first communication device to transmit information to the second communication device within a time period, time length of the second communication device to transmit information to the first communication device within a time period, and protection time slot length; S2, setting the cutoff frequencies of the first low-pass filter and the second low-pass filter, and the optical power range of the first receiving unit and the optical power range of the second receiving unit; S3, establishing a bidirectional optical communication transmission link between the first communication device and the second communication device based on the communication parameters in the half-duplex communication mode; S4, controlling the first processing unit to cache the data information from the first communication data interface to obtain first cached data, or controlling the second processing unit to cache the data information from the second communication data interface to obtain second cached data; S5, controlling the first processing unit to divide the first cache data into a plurality of data segments of preset lengths according to a preset time sequence, and performing error correction coding on each data segment according to a preset error correction coding method to obtain a first data segment, or controlling the second processing unit to divide the second cache data into a plurality of data segments of preset lengths according to a preset time sequence, and performing error correction coding on each data segment according to the preset error correction coding method to obtain a second data segment; S6, based on the communication parameters in the half-duplex communication mode, control the first processing unit to add a first channel monitoring sequence to the back end of the first data segment to obtain a first modulation parameter, and use the first modulation parameter to control the first transmitting unit to generate an intensity-modulated first optical signal, and send the intensity-modulated first optical signal into the water, or control the second processing unit to add a second channel monitoring sequence to the back end of the second data segment to obtain a second modulation parameter, and use the second modulation parameter to control the second transmitting unit to generate an intensity-modulated second optical signal, and send the intensity-modulated second optical signal into the water; S7, based on the communication parameters in the half-duplex communication mode, control the first single-photon detector to convert the intensity-modulated second optical signal into a second voltage pulse sequence, and simultaneously output the second voltage pulse sequence to the first processing unit and the first low-pass filter, control the first low-pass filter to filter the second voltage pulse sequence to obtain a second voltage signal, and output the second voltage signal to the first processing unit, or control the second single-photon detector to convert the intensity-modulated first optical signal into a first voltage pulse sequence, and simultaneously output the first voltage pulse sequence to the second processing unit and the second low-pass filter, control the second low-pass filter to filter the first voltage pulse sequence to obtain a first voltage signal, and output the first voltage signal to the second processing unit; S8, based on the communication parameters in the half-duplex communication mode, controls the first processing unit to recover the second target data information according to the second voltage signal, and outputs the second target data information through the first communication data interface, and judges the working state of the first communication device according to the second voltage signal, the second voltage pulse sequence and the optical power range of the first receiving unit; or controls the second processing unit to recover the first target data information according to the first voltage signal, and outputs the first target data information through the second communication data interface, and judges the working state of the second communication device according to the first voltage signal, the first voltage pulse sequence and the optical power range of the second receiving unit.

6. The method according to claim 5, characterized in that For a target low-pass filter, the target low-pass filter is the first low-pass filter or the second low-pass filter, Set the cutoff frequency of the target low-pass filter, including: Using a bit error meter to generate a pseudo-random binary sequence according to the communication transmission rate in the half-duplex communication mode, and based on the pseudo-random binary sequence, controlling a transmitting unit corresponding to an optical signal received by a device where the target low-pass filter is located to generate an intensity-modulated optical signal; Attenuating the intensity modulated optical signal generated by the adjustable optical attenuator, and injecting the attenuated optical signal into a single photon detector in the device where the target low-pass filter is located, so that the single photon detector generates a discrete voltage pulse sequence; Inputting the voltage pulse sequence to the target low-pass filter, and inputting the voltage signal after passing through the target low-pass filter to the bit error meter to test the bit error rate; The cutoff frequency of the target low-pass filter is adjusted so that the measured bit error rate is lower than a preset threshold value, so as to complete the setting of the cutoff frequency of the target low-pass filter.

7. The method according to claim 6, characterized in that For a target receiving unit, the target receiving unit is a first receiving unit or a second receiving unit, and setting an optical power range of the target receiving unit includes: After setting the cutoff frequency of the low-pass filter in the device where the target receiving unit is located, using the adjustable optical attenuator to increase the optical power of the single-photon detector entering the target receiving unit until the measured bit error rate is lower than the preset threshold, using an arbitrary waveform generator to generate a periodic square wave, and using the generated square wave to control the transmitting unit corresponding to the optical signal received by the target receiving unit to generate an intensity-modulated optical signal, recording the number of average voltage pulse sequences output by the single-photon detector in the target receiving unit in each period, and using the number of average voltage pulse sequences in each period to characterize the maximum optical power of the target receiving unit; The adjustable optical attenuator is used to reduce the optical power of the single-photon detector entering the target receiving unit until the measured bit error rate is lower than the preset threshold value, an arbitrary waveform generator is used to generate a periodic square wave, and the generated square wave is used to control the transmitting unit corresponding to the optical signal received by the target receiving unit to generate an intensity-modulated optical signal, and the number of average voltage pulse sequences output by the single-photon detector in the target receiving unit in each cycle is recorded, and the minimum optical power of the target receiving unit is characterized by the number of average voltage pulse sequences in each cycle.

8. The method according to claim 7, characterized in that The S3 includes: Setting the first communication device and the second communication device as a master device and a slave device respectively; The master device is controlled to transmit a link establishment signal to the slave device with a preset link switching period, the slave device is controlled to send a response signal to the master device after receiving the link establishment signal, and the master device is controlled to transmit a link establishment signal to the slave device again when detecting the response signal, and this is repeated until the master device and the slave device receive the response signal and the link establishment signal N times respectively, thereby completing the establishment of a two-way communication link, where N is a positive integer greater than or equal to 1.

9. The method according to claim 8, characterized in that Also includes: The first channel monitoring sequence and the second channel monitoring sequence are square wave sequences, and the frequency is half of the communication transmission rate; The sum of the time lengths of the first data segment and the first channel monitoring sequence is not greater than the time length of the first communication device transmitting information to the second communication device within a time period; The sum of the time lengths of the second data segment and the second channel monitoring sequence is not greater than the time length for the second communication device to transmit information to the first communication device within a time period.

10. The method according to claim 9, characterized in that The S8 comprises: Control the first processing unit to recover the second data segment and the second channel monitoring sequence from the second voltage signal according to the combination of the second channel monitoring sequence and the second data segment, control the first processing unit to perform error correction decoding according to the second data segment and a preset error correction coding method to obtain second target data information, and output the second target data information through the first communication data interface, control the first processing unit to find the total number of the second voltage pulse sequence in the corresponding time period according to the second channel monitoring sequence, and obtain the number of voltage pulse sequences in each cycle in combination with the number of cycles of the periodic square wave corresponding to the second channel monitoring sequence, and compare the obtained number of voltage pulse sequences in each cycle with the maximum optical power and minimum optical power values ​​of the first receiving unit, and use the comparison result as the working state parameter of the first communication device; or, Control the second processing unit to recover the first data segment and the first channel monitoring sequence from the first voltage signal according to the combination of the first channel monitoring sequence and the first data segment, control the second processing unit to perform error correction decoding according to the first data segment and the preset error correction coding method to obtain the first target data information, and output the first target data information through the second communication data interface, control the second processing unit to search for the total number of the first voltage pulse sequences in the corresponding time period according to the first channel monitoring sequence, and obtain the number of voltage pulse sequences in each cycle in combination with the number of cycles of the periodic square wave corresponding to the first channel monitoring sequence, and compare the obtained number of voltage pulse sequences in each cycle with the maximum optical power and minimum optical power values ​​of the second receiving unit, and use the comparison result as the working state parameter of the second communication device.

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