A light beam tracking method for underwater wireless optical communication based on photon counting

Abstract

The application provides a light beam tracking method for underwater wireless optical communication based on photon counting, relates to the technical field of laser communication, and is applied to a first optical communication device.The method comprises the following steps: establishing an optical communication link between the first optical communication device and a second optical communication device; collecting light intensity verification information and sending the light intensity verification information to the second optical communication device; receiving first feedback information generated by the second optical communication device, and judging whether the first optical communication device needs to enter a light beam tracking stage according to the first feedback information; if yes, generating scanning information and sending the scanning information to the second optical communication device; if no, continuing to communicate according to the current light beam link; receiving second feedback information generated by the second optical communication device, obtaining an optimal scanning point, and controlling a light beam of the first optical communication device to point to the optimal scanning point.The application solves the problem that light beam tracking cannot be realized when the light beam deviates, thereby causing communication interruption.

Description

Technical Field

[0001] This invention relates to the field of laser communication technology, and in particular to a beam tracking method for underwater wireless optical communication based on photon counting. Background Technology

[0002] Currently, laser communication acquisition, tracking, and aiming systems are mainly used in atmospheric communication, satellite space communication, and space-to-ground communication systems. Existing underwater wireless communication methods mainly include acoustic communication, electromagnetic wave communication, and optical communication. Although underwater wireless communication primarily uses acoustic communication, optical communication has advantages such as high transmission rate, resistance to electromagnetic interference, small device size, and low power consumption, enabling high-speed transmission of large amounts of data and showing broad application prospects in marine exploration and underwater vehicle communication.

[0003] Single-photon detection technology is developed from quantum information. Because its detection sensitivity can reach the level of a single photon, it can further increase the optical communication distance while keeping the power of the light source constant, which plays an important role in promoting the development of underwater optical communication.

[0004] Unlike other communication methods, underwater wireless optical communication technology based on photon counting receives discrete single-photon pulse signals, which presents the problem of difficulty in aligning the beams at both ends of the communication. Especially when conducting bidirectional wireless optical communication while the transmitting and receiving ends are moving simultaneously, the beam is prone to deflection, making beam tracking impossible and causing communication interruption.

[0005] Therefore, how to perform beam tracking when the beam deflects based on the signal characteristics of wireless optical communication using photon counting is a critical problem that urgently needs to be solved. Summary of the Invention

[0006] This invention provides a beam tracking method for underwater wireless optical communication based on photon counting, which solves the problem of communication interruption caused by the inability to track the beam when it deviates.

[0007] In a first aspect, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, applied to a first optical communication device, the method comprising: Establish an optical communication link between the first optical communication device and the second optical communication device; Collect light intensity verification information and send it to the second optical communication device; The system receives first feedback information generated by the second optical communication device and determines whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information. If yes, it generates scanning information and sends it to the second optical communication device. If no, it continues to communicate according to the current beam link. The system receives the second feedback information generated by the second optical communication device, obtains the optimal scanning point, and controls the beam of the first optical communication device to point to the optimal scanning point.

[0008] Furthermore, determining whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information includes: The light intensity verification result bit is obtained based on the first feedback information; wherein, the light intensity verification result bit represents the comparison result between the total photon count in the light intensity verification and the preset threshold; If the comparison result shows that the total photon count is less than or equal to a preset threshold, the first optical communication device is controlled to enter the beam tracking stage; otherwise, the first optical communication device is not controlled to enter the beam tracking stage.

[0009] Furthermore, the generation of scan information includes: With the current beam pointing point as the center, a scan is performed to obtain the number of multiple scan points and the corresponding position distribution of multiple scan points. The scan point sequence number is marked according to the number of scan points and the position distribution of scan points. Scanning information is generated based on the beam tracking stage position, the scan point sequence number position, and the light intensity verification position.

[0010] Furthermore, the distribution of the scanning points includes: a circumferential distribution with equal spacing around the current beam pointing point as the center.

[0011] Secondly, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, applied to a second optical communication device, characterized in that the method includes: Establish an optical communication link between the first optical communication device and the second optical communication device; The system receives light intensity verification information sent by the first optical communication device, counts the total photon count in the light intensity verification information, compares the total photon count with a preset threshold, generates first feedback information, and sends it to the first optical communication device. The device receives scanning information sent by the first optical communication device, selects the scanning point with the largest total photon count based on the scanning information, generates second feedback information based on the scanning point, and sends it to the first optical communication device.

[0012] Furthermore, the generation of the second feedback information includes: The light intensity value corresponding to the scan point is compared with the light intensity threshold to generate the beam tracking result bit; The optimal scan point number is obtained by taking the scan point number corresponding to that scan point. The second feedback information is generated based on the beam tracking result bit and the optimal scan point sequence bit.

[0013] Furthermore, the generation of the beam tracking result bit includes: When the light intensity value corresponding to the scan point is greater than the light intensity threshold, it indicates that beam tracking is complete; otherwise, the beam tracking stage continues.

[0014] Thirdly, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, applied to a first optical communication device and a second optical communication device that have established an optical communication link, characterized in that the method includes: The first optical communication device collects optical intensity verification information and sends it to the second optical communication device; The second optical communication device receives the light intensity verification information, counts the total photon count in the light intensity verification information, compares the total photon count with a preset threshold, generates first feedback information, and sends it to the first optical communication device. The first optical communication device receives the first feedback information and determines whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information; if yes, it generates scanning information and sends it to the second optical communication device; if no, it continues to communicate according to the current beam link. The second optical communication device receives the scanning information, selects the scanning point with the largest total photon count based on the scanning information, generates second feedback information based on the scanning point, and sends it to the first optical communication device. The first optical communication device receives the second feedback information, obtains the optimal scanning point, and controls the beam of the first optical communication device to point to the optimal scanning point.

[0015] Furthermore, the light intensity verification information includes a frame header, a light intensity verification stage bit, and a light intensity verification bit; The first feedback information includes the frame header and the light intensity verification result bits; The scanning information includes a frame header, beam tracking stage bit, scan point sequence bit, and light intensity verification bit; The second feedback information includes the frame header, beam tracking result bit, and optimal scan point sequence bit.

[0016] Furthermore, the first optical communication device or the second optical communication device includes a control chip, as well as a transmitting module and a receiving module connected to the control chip. The transmitting module includes a laser and a piezoelectric ceramic deflector, both of which are connected to the control chip; wherein, the piezoelectric ceramic deflector is used to adjust the direction of the laser beam emitted by the laser. The transmitting module includes a single-photon detector and a beam shrinker, with a filter disposed between the single-photon detector and the beam shrinker, and the single-photon detector is connected to the control chip.

[0017] In summary, this invention provides a beam tracking method for underwater wireless optical communication based on photon counting. Compared with existing technologies, the technical solution conceived in this invention can achieve the following beneficial effects: This invention collects light intensity verification information to determine whether a beam tracking phase is needed. Once the beam tracking phase is entered, the optimal scanning point is obtained through photon counting. This allows the underwater wireless optical communication to perform beam tracking at both ends when the beam deviates, automatically adjusting the beam position and achieving automatic alignment of the beams at both ends to maintain a stable communication link.

[0018] Furthermore, by using the same optical communication transceiver for the beam capture and tracking aiming system and the photon counting optical communication system, there is no need to add additional information feedback methods such as electromagnetic waves and sonar, resulting in a simpler system structure and effectively reducing the weight and cost of underwater communication devices. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating a beam tracking method for underwater wireless optical communication based on photon counting, provided by the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the laser scanning information structure of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 3 This is a schematic diagram of the light intensity verification information structure of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 4 This is a schematic diagram of the first feedback information structure of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 5 This is a schematic diagram of the scanning information structure of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 6 This is a schematic diagram of the scanning point location distribution of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 7 This is a schematic diagram of the second feedback information structure of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 8 This is a flowchart illustrating a beam tracking method for underwater wireless optical communication based on photon counting, provided by the present invention. Figure 2 ; Figure 9 This is a flowchart illustrating a beam tracking method for underwater wireless optical communication based on photon counting, provided by the present invention. Figure 3 ; Figure 10 This is a schematic diagram of the communication between the first optical communication device and the second optical communication device in a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] It should be noted that, in the description of the embodiments of the present invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a method, step, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to the method, step, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the method, step, or apparatus that includes said element.

[0023] To achieve laser capture, tracking, and aiming at both ends of underwater wireless optical communication based on photon counting, it is necessary to combine laser scanning technology and single-photon communication technology to provide information feedback before the communication link is established, thereby achieving beam tracking at both ends. This invention provides a beam tracking method for underwater wireless optical communication based on photon counting, solving the problem of communication interruption caused by the inability to track the beam when it deviates.

[0024] On the one hand, such as Figure 1 As shown, applied to a first optical communication device, the method includes: Step 101: Establish an optical communication link between the first optical communication device and the second optical communication device.

[0025] As one embodiment, a first laser signal is sent to a second optical communication device through the transmitting module of the first optical communication device. The first laser signal includes first pointing information of the first optical communication device. A second laser signal generated by the second optical communication device based on the first pointing information is obtained through the receiving module of the first optical communication device. The second laser signal includes the first pointing information and the second pointing information of the second optical communication device. Based on the first pointing information, the first optical communication device adjusts the transmission angle of the transmitting module and sends the first and second pointing information to the second optical communication device, so that the second optical communication device adjusts the transmission angle of the laser signal based on the second pointing information, thereby establishing an optical communication link between the first and second optical communication devices.

[0026] In another embodiment, a first laser signal sent by the first optical communication device is obtained through the receiving module of the second optical communication device. The first laser signal includes first pointing information of the first optical communication device. A second laser signal is sent to the first optical communication device through the transmitting module of the second optical communication device, so that the first optical communication device adjusts the emission angle of the laser signal based on the second laser signal. The second laser signal includes the first pointing information and the second pointing information of the second optical communication device. The first pointing information and the second pointing information sent by the first optical communication device are obtained through the receiving module of the second optical communication device. The emission angle of the transmitting module is adjusted based on the second pointing information to establish an optical communication link between the first optical communication device and the second optical communication device.

[0027] For example, to establish an optical communication link between a first optical communication device and a second optical communication device, assuming that during laser scanning, the signal terminal (B terminal) of the second optical communication device first receives information from the signal terminal (A terminal) of the first optical communication device, then the beam coarse alignment process includes: S1011: A-end is scanned, and the laser emits the pointing information of A-end; the "pointing information of A-end" changes point by point, while the "pointing information of B-end" is all 0. At this time, the alignment stage of A-end is "00", and the alignment stage of B-end is "00".

[0028] S1012: After receiving information from A, B obtains the pointing information from A, and the alignment phase enters stage "10". B completes the acquisition of A. B transmits the pointing information of A and B through a laser, where the "pointing information of B" changes point by point, and the "pointing information of A" is the information received from A; A remains unchanged. At this time, the alignment phase of A is "00", and the alignment phase of B is "10".

[0029] S1013: After receiving information from B, end A obtains the relevant "pointing information" sent by end B and enters stage "11," where end A completes the acquisition of end B. End A controls the two-axis reflector to point to a fixed point based on the "pointing information" received from end B, achieving laser aiming, and transmits the "pointing information of end A and end B" through the laser. Both the "pointing information of end A and end B" are fixed. At this time, the alignment stage of end A is "11," and the alignment stage of end B is "10."

[0030] S1014: After receiving information from end A, end B obtains the relevant "pointing information" sent by end A and enters stage "11". Based on the "pointing information" received from end A, end B controls the two-axis reflector to point to a fixed point, achieving laser aiming, and transmits the "pointing information from both end A and end B" via the laser. The pointing information is fixed. At this time, the alignment stage for end A is "11", and the alignment stage for end B is "11".

[0031] S1015: If both the A-end and B-end alignment stages are "11", then the acquisition and tracking aiming is considered successful, the alignment of the beams at both ends of the communication is completed, the angle of the piezoelectric ceramic deflector remains unchanged, and photon counting optical communication can be performed.

[0032] In this context, "00" indicates that both the information pointed to by end A and the information pointed to by end B are unknown; "10" indicates that the information pointed to by end A is known, and the information pointed to by end B is unknown; "01" indicates that the information pointed to by end A is unknown, and the information pointed to by end B is known; and "11" indicates that both the information pointed to by end A and the information pointed to by end B are known.

[0033] It should be noted that, as Figure 2 As shown, the information structure transmitted by the laser scanning includes a frame header, alignment stage position, A-end pointing information, and B-end pointing information.

[0034] Frame header: A specific waveform used for clock synchronization and symbol synchronization; Alignment stage bit: A fixed-length "2" bit signal that indicates the current bit alignment stage.

[0035] Pointing information at end A and end B: The pointing information is determined by the control commands sent by the FPGA main controller at each communication end to the biaxial mirror at the current scanning point and the information received by the single-photon detector. For end A, the pointing information is determined by the control commands sent to the biaxial mirror at the current scanning point, and the pointing information at end B is determined by the information sent by end B received by the single-photon detector; otherwise, it is all 0. The same applies to end B.

[0036] It should be noted that the first optical communication device and the second optical communication device are the same type of capture, tracking, and aiming devices.

[0037] Step 102: Collect light intensity verification information and send it to the second optical communication device.

[0038] As an example, the first optical communication device collects light intensity verification information at a set time interval and sends it to the second optical communication device through the transmitter of the first optical communication device.

[0039] It should be noted that, as Figure 3 As shown, the light intensity verification information includes the frame header, the light intensity verification stage bit, and the light intensity verification bit.

[0040] Frame header: A specific waveform used for clock synchronization and symbol synchronization; Light intensity verification stage bit: indicates that this frame is used for light intensity verification, which is used to distinguish it from communication data frames.

[0041] Light intensity check bit: A fixed-length "1" bit signal used to count the total number of photons in this segment at the receiver and estimate the current light intensity.

[0042] Step 103: Receive the first feedback information generated by the second optical communication device, and determine whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information; if yes, generate scanning information and send it to the second optical communication device; if no, continue to communicate according to the current beam link.

[0043] It should be noted that the information structure of the first feedback information is as follows: Figure 4 As shown, it includes the frame header and the light intensity verification result bits.

[0044] Frame header: A specific waveform used for clock synchronization and symbol synchronization.

[0045] Light intensity verification result bit: indicates the comparison result of photon count and preset threshold in light intensity verification. If it is higher than the preset threshold, it means to continue communication. If it is lower than or equal to the preset threshold, it means to enter the beam tracking stage.

[0046] As one embodiment, determining whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information includes: obtaining a light intensity verification result bit based on the first feedback information; wherein, the light intensity verification result bit represents the comparison result of the total photon count in the light intensity verification with a preset threshold; if the comparison result shows that the total photon count is less than or equal to the preset threshold, then the first optical communication device is controlled to enter the beam tracking stage; otherwise, the first optical communication device is not controlled to enter the beam tracking stage.

[0047] More specifically, the receiving end of the first optical communication device receives the first feedback information. If beam tracking is not performed, communication continues according to the current optical communication link. If beam tracking is required, the device enters the beam tracking stage and generates scanning information.

[0048] It should be noted that the information structure of the scanned information is as follows: Figure 5 As shown, it includes the frame header, beam tracking stage bit, scan point sequence bit, and light intensity check bit.

[0049] Frame header: A specific waveform used for clock synchronization and symbol synchronization; Beam tracking stage bit: Indicates that the current information frame is used for beam tracking; Scan point sequence number: Indicates the sequence number of the current scan point; for example, the correspondence of scan points is as follows: Figure 6 As shown, there are a total of 8 scan points, and the scan point sequence number is set to 3 bits in length.

[0050] Light intensity check bit: A fixed-length "1" bit signal used to count the total photons in this segment at the receiver and estimate the light intensity at the current scanning point.

[0051] If the total photon count is lower than or equal to a preset threshold, the receiver of the first optical communication device receives the first feedback information and then enters the beam tracking stage. As an example, the generation of scanning information includes: scanning outwards from the current beam pointing point to obtain multiple scan points and their corresponding position distributions; marking the scan point sequence number based on the scan point number and position distribution; and generating scanning information based on the beam tracking stage bit, the scan point sequence number bit, and the light intensity verification bit.

[0052] It should be noted that the scanning points can be randomly distributed around the current beam pointing point, or they can be distributed in a circular pattern with equal spacing around the current beam pointing point as the center. For example, they can be distributed in a centrally symmetrical manner, such as a rectangle, a circle, or a triangle, around the center point.

[0053] Step 104: Receive the second feedback information generated by the second optical communication device, obtain the optimal scanning point, and control the beam of the first optical communication device to point to the optimal scanning point.

[0054] It should be noted that the information structure of the second feedback information is as follows: Figure 7 As shown, it includes the frame header, beam tracking result bit, and optimal scan point sequence bit.

[0055] Frame header: A specific waveform used for clock synchronization and symbol synchronization; Beam tracking result bit: This indicates the result of this beam tracking. When the count value corresponding to the point with the largest total photon count in the scanned points is greater than the preset threshold, beam tracking is completed and the communication phase is resumed; if it is less than or equal to the preset threshold, beam tracking continues. Optimal scan point sequence number: This indicates the scan point sequence number corresponding to the scan point with the largest total photon count in this beam tracking. After receiving this information, the transmitting end will adjust the pointer to the position of this point.

[0056] After receiving the second feedback information, the first optical communication device controls the tilting mirror of the first optical communication device to point to the optimal scanning point number. If the beam tracking result indicates that the tracking is not completed, the scanning is performed again with the new pointing point as the center. If the beam tracking is completed, the beam tracking stage ends and photon counting optical communication can continue.

[0057] like Figure 8 As shown, applied to a second optical communication device, the method includes: Step 201: Establish an optical communication link between the first optical communication device and the second optical communication device. The technical features of this step are the same as those of step 101, and will not be repeated here.

[0058] Step 202: Receive the light intensity verification information sent by the first optical communication device, count the total photon count in the light intensity verification information, compare the total photon count with a preset threshold, generate first feedback information and send it to the first optical communication device.

[0059] In other words, when the receiver of the second optical communication device detects the light intensity verification information, it counts the total number of photons in the light intensity verification bit and compares it with a preset threshold to determine whether to perform beam tracking.

[0060] It should be noted that the information structure of the first feedback information is as follows: Figure 4 As shown, it includes the frame header and the light intensity verification result bits.

[0061] Frame header: A specific waveform used for clock synchronization and symbol synchronization.

[0062] Light intensity verification result bit: indicates the comparison result of photon count and preset threshold in light intensity verification. If it is higher than the preset threshold, it means to continue communication. If it is lower than or equal to the preset threshold, it means to enter the beam tracking stage.

[0063] For example, if the single-photon detector used by the system has a photon pair resolution of 20ns and a total length of 1ms for the light intensity check bit, then theoretically the maximum photon count per second is 50,000. If the photon count threshold is set to 35,000, then if the actual photon count is greater than 35,000, then beam tracking is not required and communication continues; if the photon count is less than or equal to 35,000, then communication is paused and beam tracking is performed.

[0064] Step 203: Receive scanning information sent by the first optical communication device, select the scanning point with the largest total photon count based on the scanning information, generate second feedback information based on the scanning point and send it to the first optical communication device.

[0065] The information structure of the scanned information is as follows: Figure 5As shown, it includes the frame header, beam tracking stage bit, scan point sequence bit, and light intensity check bit.

[0066] Frame header: A specific waveform used for clock synchronization and symbol synchronization; Beam tracking stage bit: Indicates that the current information frame is used for beam tracking; Scan point sequence number: Indicates the sequence number of the current scan point; for example, the correspondence of scan points is as follows: Figure 6 As shown, there are a total of 8 scan points, and the scan point sequence number is set to 3 bits in length.

[0067] Light intensity check bit: A fixed-length "1" bit signal used to count the total photons in this segment at the receiver and estimate the light intensity at the current scanning point.

[0068] The information structure of the second feedback information is as follows: Figure 7 As shown, it includes the frame header, beam tracking result bit, and optimal scan point sequence bit.

[0069] Frame header: A specific waveform used for clock synchronization and symbol synchronization; Beam tracking result bit: This indicates the result of this beam tracking. When the count value corresponding to the point with the largest total photon count in the scanned points is greater than the preset threshold, beam tracking is completed and the communication phase is resumed; if it is less than or equal to the preset threshold, beam tracking continues. Optimal scan point sequence number: This indicates the scan point sequence number corresponding to the scan point with the largest total photon count in this beam tracking. After receiving this information, the transmitting end will adjust the pointer to the position of this point.

[0070] As one embodiment, the generation of the second feedback information includes: comparing the light intensity value corresponding to the scan point with a light intensity threshold to generate a beam tracking result bit; obtaining the optimal scan point sequence bit from the scan point sequence bit corresponding to the scan point; and generating the second feedback information based on the beam tracking result bit and the optimal scan point sequence bit.

[0071] Furthermore, the generation of the beam tracking result bit includes: when the light intensity value corresponding to the scanning point is greater than the light intensity threshold, it indicates that beam tracking is complete; otherwise, the beam tracking stage continues.

[0072] As one embodiment, after receiving the scanning information sent by the first optical communication device, the scanning point number and the total photon count value of the corresponding light intensity check bit are recorded. After all scanning points have been recorded, the scanning point with the largest total photon count value is selected, and the light intensity value corresponding to this point is compared with a preset threshold. Then, second feedback information is sent to the first optical communication device.

[0073] like Figure 9As shown, the method, applied to a first optical communication device and a second optical communication device that have established an optical communication link, includes: Step 301: The first optical communication device collects optical intensity verification information and sends it to the second optical communication device; Step 302: The second optical communication device receives the light intensity verification information, counts the total photon count in the light intensity verification information, compares the total photon count with a preset threshold, generates first feedback information, and sends it to the first optical communication device. Step 303: The first optical communication device receives the first feedback information and determines whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information; if yes, it generates scanning information and sends it to the second optical communication device; if no, it continues to communicate according to the current beam link. Step 304: The second optical communication device receives the scanning information, selects the scanning point with the largest total photon count based on the scanning information, generates second feedback information based on the scanning point, and sends it to the first optical communication device; Step 305: The first optical communication device receives the second feedback information, obtains the optimal scanning point, and controls the beam of the first optical communication device to point to the optimal scanning point.

[0074] As a specific example, such as Figure 10 As shown, (1) During the process of photon counting optical communication after coarse beam alignment, A sends light intensity verification information to B every once in a while. The light intensity verification information includes a fixed-length “1” bit signal, which is used to count the total number of photons in the segment and estimate the current light intensity for the receiving end.

[0075] (2) After detecting the light intensity verification frame, the B end counts the total number of photons in the light intensity verification bit and compares it with the preset threshold to determine whether to perform beam tracking, and then sends light intensity feedback information to the A end.

[0076] (3) If the number of photons counted is lower than or equal to the threshold, then after receiving the feedback information, end A enters the beam tracking stage. During the beam tracking stage, end A scans around the current pointing point, and sends information through the laser at the same time.

[0077] (4) After receiving the information, B records the scan point number and the total photon count value of the light intensity check bit corresponding to that point. After all scan points have been recorded, B selects the scan point with the largest total photon count value, compares the light intensity value corresponding to that point with the preset threshold, and sends feedback information to the transmitting end, informing A of the scan point number with the largest photon count value and the result of the comparison with the threshold.

[0078] (5) After receiving the above feedback information, A controls the swing mirror to point to the optimal scanning point number. If the beam tracking result shows that the tracking is not completed, the new pointing point is used as the center and step (3) is repeated. If the beam tracking is completed, the beam tracking stage ends and photon counting optical communication can continue.

[0079] It should be noted that the first optical communication device or the second optical communication device includes a control chip, as well as a transmitting module and a receiving module that are connected to the control chip. The transmitting module includes a laser and a piezoelectric ceramic deflector, both of which are connected to a control chip; wherein, the piezoelectric ceramic deflector is used to adjust the direction of the laser beam emitted by the laser. The transmitting module includes a single-photon detector and a beam shrinker, with a filter placed between the single-photon detector and the beam shrinker, and the single-photon detector is connected to the control chip.

[0080] In other words, both parties in the communication include a transmitting device and a receiving device, and after alignment, bidirectional high-speed photon counting optical communication can be carried out.

[0081] The transmitting device includes laser scanning and transmission functions, and can serve as a communication transmitter after alignment. The control chip acts as the main controller, controlling the laser and the biaxial piezoelectric ceramic deflector. The biaxial piezoelectric ceramic deflector adjusts its mirror angle according to the control signals received from the control chip. The control chip controls the biaxial piezoelectric ceramic deflector, causing it to deflect at a certain pattern and frequency, achieving laser scanning with a specific trajectory, step size, and frequency in conjunction with the laser. The control chip sends control commands to the biaxial piezoelectric ceramic deflector according to different scanning points, controlling the laser to emit light and transmitting corresponding information in a specific modulation mode, thus achieving synchronous scanning and transmission.

[0082] The receiving device extracts the information sent by the other end of the communication system and can act as the receiving end of the communication system after alignment is completed.

[0083] The beam expander focuses the received beam, which is then filtered by a specific wavelength filter and detected by a single-photon detector. The single-photon detector outputs a single-photon pulse, which is sent to the control chip. The control chip acts as the main controller, processes the single-photon pulse, extracts relevant information based on a preset information structure, and controls the laser scanning and the information emitted by the laser during scanning according to the capture, tracking, and aiming algorithm.

[0084] The control chip can be an FPGA chip.

[0085] The laser wavelength can be between 450nm and 550nm. Furthermore, different wavelengths of laser light can be used at the two ends of the device, for example, a 488nm laser and a 532nm laser can be used at the two ends respectively.

[0086] Single-photon detectors are used for detecting weak light signals and can enable automatic acquisition and aiming at both ends of a communication system that receives light intensity on the order of a single photon.

[0087] In summary, this invention provides a beam tracking method for underwater wireless optical communication based on photon counting. During the beam acquisition, tracking, and aiming process, information feedback is provided using photon counting optical communication. Furthermore, the laser acquisition, tracking, and aiming system and the photon counting optical communication system use the same set of information transceivers, enabling automatic beam alignment between underwater vehicles, seabed detectors, and atmospheric aircraft. It allows for bidirectional high-speed single-photon-level optical communication and beam tracking when the beam deviates, maintaining the stability of the communication link.

[0088] It should be noted that, for the sake of simplicity, the foregoing embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0089] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0090] In the several embodiments provided in this application, it should be understood that the disclosed methods or systems can be implemented in other ways. For example, the embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0091] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0092] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0093] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage device. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0094] Those skilled in the art will understand that all or part of the circuits in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: a flash drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0095] The foregoing description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

[0096] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0097] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A beam tracking method for underwater wireless optical communication based on photon counting, applied to a first optical communication device, characterized in that, The method includes: Establish an optical communication link between the first optical communication device and the second optical communication device; Collect light intensity verification information and send it to the second optical communication device; The system receives first feedback information generated by the second optical communication device. The first feedback information includes a frame header and a light intensity verification result bit, wherein the light intensity verification result bit represents the comparison result between the total photon count in the light intensity verification and a preset threshold. Based on the first feedback information, determine whether to control the first optical communication device to enter the beam tracking stage; if the comparison result shows that the total photon count is less than or equal to a preset threshold, then control the first optical communication device to enter the beam tracking stage, scan around the current beam pointing point as the center, generate scanning information and send it to the second optical communication device, the scanning information including frame header, beam tracking stage bit, scan point sequence number bit and light intensity check bit; if not, continue to communicate according to the current beam link; The system receives the second feedback information generated by the second optical communication device, obtains the optimal scanning point sequence number, and controls the beam of the first optical communication device to point to the optimal scanning point according to the optimal scanning point sequence number.

2. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 1, characterized in that, The generation of scan information includes: With the current beam pointing point as the center, a scan is performed to obtain the number of multiple scan points and the corresponding position distribution of multiple scan points. The scan point sequence number is marked according to the number of scan points and the position distribution of scan points. Scanning information is generated based on the beam tracking stage position, the scan point sequence number position, and the light intensity verification position.

3. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 2, characterized in that, The distribution of scanning points includes: a ring-shaped distribution with equal spacing around the current beam pointing point as the center.

4. A beam tracking method for underwater wireless optical communication based on photon counting, applied to a second optical communication device, characterized in that, The method includes: Establish an optical communication link between the first optical communication device and the second optical communication device; The system receives light intensity verification information sent by the first optical communication device, counts the total photon count in the light intensity verification information, compares the total photon count with a preset threshold, generates first feedback information, and sends it to the first optical communication device. The first feedback information includes a frame header and a light intensity verification result bit, wherein the light intensity verification result bit represents the comparison result between the total photon count in the light intensity verification and the preset threshold. The system receives scanning information sent by the first optical communication device. The scanning information includes a frame header, a beam tracking stage bit, a scan point sequence number bit, and a light intensity check bit. Based on the scanning information, the system selects the scan point with the largest total photon count value, generates second feedback information based on the scan point, and sends it to the first optical communication device. The generation of the second feedback information includes: comparing the light intensity value corresponding to the scan point with a light intensity threshold to generate a beam tracking result bit; obtaining the optimal scan point sequence number bit from the scan point sequence number bit; and generating the second feedback information based on the beam tracking result bit and the optimal scan point sequence number bit.

5. A beam tracking method for underwater wireless optical communication based on photon counting according to claim 4, characterized in that, The generation of the beam tracking result bit includes: when the light intensity value corresponding to the scanning point is greater than the light intensity threshold, it indicates that beam tracking is completed; otherwise, the beam tracking stage continues.

6. A beam tracking method for underwater wireless optical communication based on photon counting, applied to a first optical communication device and a second optical communication device that have established an optical communication link, characterized in that... The method includes: The first optical communication device collects optical intensity verification information and sends it to the second optical communication device; The second optical communication device receives the optical intensity verification information, counts the total photon count in the optical intensity verification information, compares the total photon count with a preset threshold, generates first feedback information, and sends it to the first optical communication device; the first feedback information includes a frame header and an optical intensity verification result bit, the optical intensity verification result bit representing the comparison result of the total photon count in the optical intensity verification with the preset threshold; The first optical communication device receives the first feedback information and determines whether to control the first optical communication device to enter the beam tracking stage based on the first feedback information; if the comparison result shows that the total photon count is less than or equal to a preset threshold, the first optical communication device is controlled to enter the beam tracking stage, and scans around the current beam pointing point as the center, generates scanning information and sends it to the second optical communication device; otherwise, communication continues according to the current beam link. The second optical communication device receives the scanning information, which includes a frame header, a beam tracking stage bit, a scan point sequence number bit, and a light intensity check bit. Based on the scanning information, it selects the scan point with the largest total photon count value, generates second feedback information based on the scan point, and sends it to the first optical communication device. The generation of the second feedback information includes: comparing the light intensity value corresponding to the scan point with a light intensity threshold to generate a beam tracking result bit; obtaining the optimal scan point sequence number bit from the scan point sequence number bit; and generating the second feedback information based on the beam tracking result bit and the optimal scan point sequence number bit. The first optical communication device receives the second feedback information, obtains the optimal scanning point sequence number, and controls the beam of the first optical communication device to point to the optimal scanning point according to the optimal scanning point sequence number.

7. A beam tracking method for underwater wireless optical communication based on photon counting according to claim 6, characterized in that, The light intensity verification information includes a frame header, a light intensity verification stage bit, and a light intensity verification bit. The first feedback information includes the frame header and the light intensity verification result bits; The scanning information includes a frame header, beam tracking stage bit, scan point sequence bit, and light intensity verification bit; The second feedback information includes the frame header, beam tracking result bit, and optimal scan point sequence bit.

8. A beam tracking method for underwater wireless optical communication based on photon counting according to claim 7, characterized in that, The first optical communication device or the second optical communication device includes a control chip, and a transmitting module and a receiving module connected to the control chip. The transmitting module includes a laser and a piezoelectric ceramic deflector, both of which are connected to the control chip; wherein, the piezoelectric ceramic deflector is used to adjust the direction of the laser beam emitted by the laser. The transmitting module includes a single-photon detector and a beam shrinker, with a filter disposed between the single-photon detector and the beam shrinker, and the single-photon detector is connected to the control chip.

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