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

Abstract

The invention provides a light beam tracking method for underwater wireless optical communication based on photon counting, which relates to the technical field of laser communication, is applied to a first optical communication device, and 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; first feedback information generated by the second optical communication device is received, and whether the first optical communication device is controlled to enter a light beam tracking stage or not is judged according to the first feedback information; if yes, scanning information is generated and sent to the second optical communication device; if not, continuing to carry out communication according to the current light beam link; and receiving second feedback information generated by the second optical communication device to obtain an optimal scanning point, and controlling the light beam of the first optical communication device to point to the optimal scanning point. According to the invention, the problem of communication interruption caused by incapability of realizing light beam tracking during light beam deviation is solved.

Description

Technical Field

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

[0002] At present, the capture, tracking and aiming systems for laser communication are mainly used in atmospheric communication, satellite space communication and satellite-to-ground communication systems. The existing underwater wireless communication methods mainly include acoustic communication, electromagnetic wave communication and optical communication. Although acoustic communication is currently the main underwater wireless communication method, optical communication has the advantages of high transmission rate, anti-electromagnetic interference, small equipment size and low energy consumption. It can transmit a large amount of data at high speed and has broad application prospects in ocean exploration, underwater submersible communication and other aspects.

[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 light source power unchanged, which plays an important role in promoting the development of underwater optical communications.

[0004] Unlike other communication methods, the underwater wireless optical communication technology based on photon counting receives discrete single-photon pulse signals, and there is a problem of difficulty in aligning the light beams at both ends of the communication. Especially when bidirectional wireless optical communication is carried out while the transmitter and the receiver are moving at the same time, the light beam can easily shift, making it impossible to achieve beam tracking, resulting in communication interruption.

[0005] Therefore, how to perform beam tracking when the beam is offset based on the signal characteristics of wireless optical communication based on photon counting is a key issue that needs to be solved urgently. Summary of the invention

[0006] The present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, which is used to solve the problem that beam tracking cannot be achieved when the beam is offset, resulting in communication interruption.

[0007] In a first aspect, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, which is applied to a first optical communication device, and the method comprises: establishing an optical communication link between the first optical communication device and the second optical communication device; Collecting light intensity verification information and sending it to the second optical communication device; receiving first feedback information generated by the second optical communication device, and determining whether to control the first optical communication device to enter a beam tracking phase according to the first feedback information; if so, generating scanning information and sending it to the second optical communication device; if not, continuing to communicate according to the current beam link; The second feedback information generated by the second optical communication device is received to obtain an optimal scanning point, and the light beam of the first optical communication device is controlled to point to the optimal scanning point.

[0008] Further, judging whether to control the first optical communication device to enter a beam tracking phase according to the first feedback information includes: Obtaining a light intensity verification result bit according to the first feedback information; wherein the light intensity verification result bit represents a comparison result between a total photon count in the light intensity verification and a preset threshold value; If the comparison result shows that the total photon count is less than or equal to the 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 scanning information includes: Taking the current beam pointing point as the center, scan the surrounding area to obtain a plurality of scanning point numbers and a plurality of corresponding scanning point position distributions, and mark the scanning point sequence number bits according to the scanning point numbers and scanning point position distributions; The scanning information is generated based on the beam tracking stage bit, the scanning point sequence number bit and the light intensity check bit.

[0010] Furthermore, the scanning point position distribution includes: with the current light beam pointing point as the center, the scanning point position distribution is equidistantly distributed around the current light beam pointing point.

[0011] In a second aspect, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, which is applied to a second optical communication device, and is characterized in that the method comprises: establishing an optical communication link between the first optical communication device and the second optical communication device; receiving light intensity verification information sent by the first optical communication device, counting total photon counts in the light intensity verification information, comparing the total photon count with a preset threshold, generating first feedback information and sending the first feedback information to the first optical communication device; The scanning information sent by the first optical communication device is received, a scanning point with a maximum total photon count value is selected based on the scanning information, and second feedback information is generated according to the scanning point and sent to the first optical communication device.

[0012] Furthermore, the generation of the second feedback information includes: Compare the light intensity value corresponding to the scanning point with the light intensity threshold to generate a beam tracking result bit; The scanning point sequence number corresponding to the scanning point is used to obtain the best scanning point sequence number; Second feedback information is generated based on the beam tracking result bit and the optimal scanning point sequence number bit.

[0013] Further, 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 means that the beam tracking is completed; otherwise, the beam tracking stage continues.

[0014] In a third aspect, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, which is applied to a first optical communication device and a second optical communication device that have established an optical communication link, and is characterized in that the method comprises: The first optical communication device collects light 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 phase according to the first feedback information; if so, generates scanning information and sends it to the second optical communication device; if not, continues to communicate according to the current beam link; The second optical communication device receives the scanning information, selects a scanning point with a maximum total photon count value based on the scanning information, generates second feedback information according to the scanning point, and sends the second feedback information to the first optical communication device; The first optical communication device receives the second feedback information, obtains an optimal scanning point, and controls the light beam of the first optical communication device to point to the optimal scanning point.

[0015] Further, 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 a frame header and a light intensity check result bit; The scanning information includes a frame header, a beam tracking stage bit, a scanning point sequence number bit and a light intensity check bit; The second feedback information includes a frame header, a beam tracking result bit, and an optimal scanning point sequence number bit.

[0016] Furthermore, 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 at the same time; The transmitting module includes a laser and a piezoelectric ceramic deflection mirror, and both the laser and the piezoelectric ceramic deflection mirror are connected to the control chip; wherein the piezoelectric ceramic deflection mirror is used to adjust the direction of the laser beam emitted by the laser; The emission module comprises a single-photon detector and a beam-shrinking mirror, a filter is arranged between the single-photon detector and the beam-shrinking mirror, and the single-photon detector is connected to the control chip.

[0017] In general, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting. The technical solution conceived by the present invention can achieve the following beneficial effects compared with the prior art: The present invention determines whether a beam tracking stage is required by collecting light intensity verification information. When entering the beam tracking stage, the optimal scanning point is obtained by photon counting. Therefore, when the light beam is offset, the two ends of the underwater wireless optical communication can perform beam tracking, automatically adjust the beam position, realize automatic alignment of the light beams at both ends, and keep the communication link stable.

[0018] In addition, by using the same optical communication transceiver for the beam capture tracking and 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. The system structure is simpler and can effectively reduce the weight and cost of underwater communication equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 The present invention provides a method flow diagram of a beam tracking method for underwater wireless optical communication based on photon counting. Figure 1 ; Figure 2 It 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 It is a schematic diagram of the light intensity verification information structure of a light beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 4 It is a schematic diagram of a 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 It 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 It is a schematic diagram of the position distribution of scanning points of a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention; Figure 7 It is a schematic diagram of a 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 The present invention provides a method flow diagram of a beam tracking method for underwater wireless optical communication based on photon counting. Figure 2 ; Fig. 9 The present invention provides a method flow diagram of a beam tracking method for underwater wireless optical communication based on photon counting. Figure 3 ; Fig.10 It is a communication schematic diagram of a first optical communication device and a second optical communication device in a beam tracking method for underwater wireless optical communication based on photon counting provided by the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0022] It should be noted that, in the description of the embodiments of the present invention, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a method, step or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such method, step or device. In the absence of further restrictions, the elements defined by the sentence "include a ..." do not exclude the existence of other identical elements in the method, step or device including the elements.

[0023] In order to realize 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, and perform information feedback when the communication link has not been established to realize beam tracking at both ends. The present invention provides a beam tracking method for underwater wireless optical communication based on photon counting, which solves the problem that beam tracking cannot be realized when the beam is offset, resulting in communication interruption.

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

[0025] As an embodiment, a first laser signal is sent to a second optical communication device through a transmitting module of a first optical communication device, the first laser signal including 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 a receiving module of the first optical communication device, the second laser signal including the first pointing information and the second pointing information of the second optical communication device; the first optical communication device adjusts the emission angle of the transmitting module based on the first pointing information, and sends the first pointing information and the second pointing information to the second optical communication device, so that the second optical communication device adjusts the emission angle of the laser signal based on the second pointing information, thereby establishing an optical communication link between the first optical communication device and the second optical communication device.

[0026] As another embodiment, a first laser signal sent by a first optical communication device is acquired through a receiving module of a second optical communication device, the first laser signal including first directional information of the first optical communication device; a second laser signal is sent to the first optical communication device through a 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 including first directional information and second directional information of the second optical communication device; the first directional information and second directional information sent by the first optical communication device are acquired through a receiving module of the second optical communication device, the emission angle of the transmitting module is adjusted based on the second directional information, and an optical communication link is established between the first optical communication device and the second optical communication device.

[0027] For example, an optical communication link is established between a first optical communication device and a second optical communication device. Assuming that during the laser scanning process, the signal end (end B) of the second optical communication device first receives information from the signal end (end A) of the first optical communication device, the rough alignment process of the light beam includes: S1011: End A scans and sends out end A pointing information through laser; the "end A pointing information" changes point by point, and the "end B pointing information" is all 0. At this time, the end A alignment stage is "00", and the end B alignment stage is "00".

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

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

[0030] S1014: After receiving the information from end A, end B obtains the relevant "pointing information" sent by end A and enters the "11" stage. End B controls the two-axis reflector to point to the fixed point based on the "B-end pointing information" received from end A, realizes laser aiming, and sends "A-end and B-end pointing information" through the laser. The pointing information is fixed. At this time, the A-end alignment stage is "11", and the B-end alignment stage is "11".

[0031] S1015: If the alignment stages of both ends A and B are "11", it is considered that the capture, tracking and aiming are successful, the alignment of the light beams at both ends of the communication is completed, the angle of the piezoelectric ceramic deflection mirror remains unchanged, and photon counting optical communication can be carried out.

[0032] Among them, "00" means that both the A-end pointing information and the B-end pointing information are unknown; "10" means that the A-end pointing information is known, but the B-end pointing information is unknown; "01" means that the A-end pointing information is unknown, but the B-end pointing information is known; "11" means that both the A-end pointing information and the B-end pointing information are known.

[0033] It should be noted that if Figure 2 As shown, the information structure sent by the laser scanning includes a frame header, an alignment phase bit, 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 indicating the current bit alignment stage.

[0035] Pointing information of end A and end B: The pointing information is determined by the control instructions sent by the FPGA main controller of each communication end to the two-axis reflector at the current scanning point and the information received by the single-photon detector. For end A, the pointing information of end A is determined by the control instructions sent to the two-axis reflector corresponding to the current scanning point, and the pointing information of end B is determined by the information sent by end B received by the single-photon detector, otherwise it is all 0; the opposite is true for 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 embodiment, the first optical communication device collects light intensity verification information at every set time interval, and sends the information to the second optical communication device through the transmitting end of the first optical communication device.

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

[0040] Frame header: a specific waveform used for clock synchronization and symbol synchronization; Light intensity verification stage bit: indicates that the frame is used for light intensity verification and 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 photon count in the segment for the receiving end to 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 phase according to the first feedback information; if so, generate scanning information and send it to the second optical communication device; if not, 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 check result bit.

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

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

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

[0047] More specifically, the receiving end of the first optical communication device receives the first feedback information, and if beam tracking is not performed, it continues to communicate according to the current optical communication link; if beam tracking is required, it enters the beam tracking phase to generate scanning information.

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

[0049] Frame header: a specific waveform used for clock synchronization and symbol synchronization; Beam tracking phase 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 corresponding relationship of the scan points is as follows Figure 6 As shown, there are 8 scanning points in total, and the length of the scanning point sequence number is set to 3 bits.

[0050] Light intensity check bit: A fixed-length "1" bit signal used to count the total photon count of the segment for the receiving end to estimate the light intensity of the current scanning point.

[0051] If the total photon count is lower than or equal to the preset threshold, the receiving end of the first optical communication device enters the beam tracking stage after receiving the first feedback information. As an embodiment, the generation of scanning information includes: taking the current beam pointing point as the center, scanning around to obtain a plurality of scanning point numbers and a plurality of corresponding scanning point position distributions, marking the scanning point sequence number bit according to the scanning point number and the scanning point position distribution; generating scanning information based on the beam tracking stage bit, the scanning point sequence number bit and the light intensity check bit.

[0052] It should be noted that the scanning point positions can be randomly distributed around the current beam pointing point, or can be distributed around the current beam pointing point with equal spacing around the current beam pointing point. 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: receiving second feedback information generated by the second optical communication device, obtaining an optimal scanning point, and controlling the light 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 a frame header, a beam tracking result bit, and an optimal scanning point sequence number bit.

[0055] Frame header: a specific waveform used for clock synchronization and symbol synchronization; Beam tracking result bit: indicates the result of the beam tracking. When the count value corresponding to the point with the largest total photon count among the scanning points is greater than the preset threshold, the beam tracking is completed and returns to the communication stage; when it is less than or equal to the preset threshold, the beam tracking continues; Best scanning point number: indicates the scanning point number corresponding to the scanning point with the largest total photon count in this beam tracking. After receiving this information, the sending end will adjust the direction to the position of this point.

[0056] After the first optical communication device receives the second feedback information, it controls the swing mirror of the first optical communication device to point to the point according to the sequence number of the best scanning point. If the beam tracking result shows that the tracking is not completed, it scans again with the new pointing point as the center; if the beam tracking is completed, the beam tracking stage is ended 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: Establishing an optical communication link between the first optical communication device and the second optical communication device. The technical features of this step are consistent with those of step 101, and will not be described in detail here.

[0058] Step 202: receiving light intensity verification information sent by the first optical communication device, counting the total photon count in the light intensity verification information, comparing the total photon count with a preset threshold, generating first feedback information and sending it to the first optical communication device.

[0059] In other words, after the receiving end of the second optical communication device detects the light intensity verification information, it counts the total photon count in the light intensity verification bit and compares it with the 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 check result bit.

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

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

[0063] For example: the single-photon detector used in the system has a photon pair resolution of 20ns and the total length of the light intensity check bit is 1ms. The theoretical 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, there is no need to perform beam tracking and communication continues; if the photon count is less than or equal to 35,000, communication is suspended and beam tracking is performed.

[0064] Step 203: receiving scanning information sent by the first optical communication device, selecting a scanning point with a maximum total photon count value based on the scanning information, generating second feedback information according to the scanning point, and sending the second feedback information to the first optical communication device.

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

[0066] Frame header: a specific waveform used for clock synchronization and symbol synchronization; Beam tracking phase 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 corresponding relationship of the scan points is as follows Figure 6 As shown, there are 8 scanning points in total, and the length of the scanning point sequence number is set to 3 bits.

[0067] Light intensity check bit: A fixed-length "1" bit signal used to count the total photon count of the segment for the receiving end to estimate the light intensity of the current scanning point.

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

[0069] Frame header: a specific waveform used for clock synchronization and symbol synchronization; Beam tracking result bit: indicates the result of the beam tracking. When the count value corresponding to the point with the largest total photon count among the scanning points is greater than the preset threshold, the beam tracking is completed and returns to the communication stage; when it is less than or equal to the preset threshold, the beam tracking continues; Best scanning point number: indicates the scanning point number corresponding to the scanning point with the largest total photon count in this beam tracking. After receiving this information, the sending end will adjust the direction to the position of this point.

[0070] As an embodiment, the generation of the second feedback information includes: comparing the light intensity value corresponding to the scanning point with the light intensity threshold to generate a beam tracking result bit; obtaining the best scanning point number bit from the scanning point sequence bit corresponding to the scanning point; and generating the second feedback information based on the beam tracking result bit and the best scanning 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 the beam tracking is completed; otherwise, the beam tracking stage continues.

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

[0073] like Fig. 9As shown, the method is applied to a first optical communication device and a second optical communication device that establish an optical communication link, and includes: Step 301: The first optical communication device collects light 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 phase according to the first feedback information; if so, generates scanning information and sends it to the second optical communication device; if not, continues to communicate according to the current beam link; Step 304: The second optical communication device receives the scanning information, selects a scanning point with the largest total photon count value based on the scanning information, generates second feedback information according to the scanning point, and sends the second feedback information to the first optical communication device; Step 305: The first optical communication device receives the second feedback information, obtains an optimal scanning point, and controls the light beam of the first optical communication device to point to the optimal scanning point.

[0074] As a specific example, Fig.10 As shown, (1) During the photon counting optical communication process after the light beam is roughly aligned, end A sends light intensity verification information to end B at regular intervals. The light intensity verification information includes a fixed-length "1" bit signal, which is used to count the total photon count of the segment for the receiving end and estimate the current light intensity.

[0075] (2) After end B detects the light intensity check frame, it counts the total photon count in the light intensity check bit and compares it with the preset threshold to decide whether to perform beam tracking, and then sends light intensity feedback information to end A.

[0076] (3) If the counted photon count is lower than or equal to the threshold, end A enters the beam tracking phase after receiving the feedback information. In the beam tracking phase, end A scans the surrounding area with the current pointing point as the center, and sends information through the laser during the scanning.

[0077] (4) After receiving the information, end B records the scanning point number and the total photon count value of the light intensity check bit corresponding to the point. When all scanning points are recorded, the scanning point with the largest total photon count value is selected, and the light intensity value corresponding to the point is compared with the preset threshold. Feedback information is sent to the sending end to inform end A of the number of the scanning point with the largest photon count value and the result of the comparison with the threshold.

[0078] (5) After receiving the above feedback information, end A controls the swing mirror to point to the optimal scanning point according to the sequence number of the optimal scanning point. If the beam tracking result shows that the tracking is not completed, step (3) is repeated with the new pointing point as the center. If the beam tracking is completed, the beam tracking stage is ended 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, and a transmitting module and a receiving module connected to the control chip at the same time; The transmitting module includes a laser and a piezoelectric ceramic deflection mirror, both of which are connected to a control chip; wherein the piezoelectric ceramic deflection mirror is used to adjust the direction of the laser beam emitted by the laser; The emission module comprises a single-photon detector and a beam-shrinking mirror, a filter is arranged between the single-photon detector and the beam-shrinking mirror, and the single-photon detector is connected to a control chip.

[0080] That is to say, both communicating parties include a transmitting device and a receiving device, and after alignment is completed, bidirectional high-speed photon counting optical communication can be carried out.

[0081] The transmitting device includes laser scanning and signaling functions, and can be used as the transmitting end of communication after alignment is completed. Among them, the control chip acts as the main controller to control the laser and the two-axis piezoelectric ceramic deflection mirror; the two-axis piezoelectric ceramic deflection mirror adjusts the mirror angle according to the control signal received from the control chip. The control chip controls the two-axis piezoelectric ceramic deflection mirror to deflect the deflection mirror in a certain pattern and frequency, and combines with the laser to achieve laser scanning with a certain trajectory, step length and frequency; the control chip gives the two-axis piezoelectric ceramic deflection mirror control instructions according to different scanning points, controls the laser to emit light, and sends corresponding information in a certain modulation method to achieve scanning and signaling synchronization.

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

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

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

[0085] The wavelength of the laser can be 450nm to 550nm. In addition, lasers of different wavelengths can be used at both ends of the device, for example, 488nm laser and 532nm laser are used at both ends respectively.

[0086] Single-photon detectors are used for weak light signal detection and can achieve automatic capture and aiming at both ends of a communication system where the received light intensity is at the single-photon level.

[0087] In summary, the present invention provides a beam tracking method for underwater wireless optical communication based on photon counting. During the process of beam capture, tracking and aiming, information feedback uses photon counting optical communication, and the laser capture, tracking and aiming system and the photon counting optical communication system use the same set of information transceiver devices, thereby realizing automatic beam alignment between underwater submersibles, seabed detectors, and aircraft in the atmosphere, etc., and can perform bidirectional high-speed single-photon optical communication, and perform beam tracking when the beam is offset to maintain the stability of the communication link.

[0088] It should be noted that, for the above-mentioned various embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0089] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

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

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

[0092] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0093] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or the whole or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a memory, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0094] Those skilled in the art will appreciate that all or part of the various circuits in the above embodiments may be completed by entering a program to instruct related hardware, and the program may be stored in a computer-readable memory, 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 above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0096] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope 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 comprises: establishing an optical communication link between the first optical communication device and the second optical communication device; Collecting light intensity verification information and sending it to the second optical communication device; receiving first feedback information generated by the second optical communication device, and determining whether to control the first optical communication device to enter a beam tracking phase according to the first feedback information; if so, generating scanning information and sending it to the second optical communication device; if not, continuing to communicate according to the current beam link; The second feedback information generated by the second optical communication device is received to obtain an optimal scanning point, and the light beam of the first optical communication device is controlled to point to the optimal scanning point.

2. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 1 is characterized in that: Determining whether to control the first optical communication device to enter a beam tracking phase according to the first feedback information includes: Obtaining a light intensity verification result bit according to the first feedback information; wherein the light intensity verification result bit represents a comparison result between a total photon count in the light intensity verification and a preset threshold value; If the comparison result shows that the total photon count is less than or equal to the 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.

3. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 1 is characterized in that: The generation of scan information includes: Taking the current beam pointing point as the center, scan the surrounding area to obtain a plurality of scanning point numbers and a plurality of corresponding scanning point position distributions, and mark the scanning point sequence number bits according to the scanning point numbers and scanning point position distributions; The scanning information is generated based on the beam tracking stage bit, the scanning point sequence number bit and the light intensity check bit.

4. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 3 is characterized in that: The scanning point position distribution includes: taking the current light beam pointing point as the center and surrounding the current light beam pointing point in a surrounding and equidistant distribution.

5. 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 comprises: establishing an optical communication link between the first optical communication device and the second optical communication device; receiving light intensity verification information sent by the first optical communication device, counting total photon counts in the light intensity verification information, comparing the total photon count with a preset threshold, generating first feedback information and sending the first feedback information to the first optical communication device; The scanning information sent by the first optical communication device is received, a scanning point with a maximum total photon count value is selected based on the scanning information, and second feedback information is generated according to the scanning point and sent to the first optical communication device.

6. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 5 is characterized in that: The generation of the second feedback information includes: Compare the light intensity value corresponding to the scanning point with the light intensity threshold to generate a beam tracking result bit; The scanning point sequence number corresponding to the scanning point is used to obtain the best scanning point sequence number; Second feedback information is generated based on the beam tracking result bit and the optimal scanning point sequence number bit.

7. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 6 is characterized in that: The generation of the beam tracking result bits includes: When the light intensity value corresponding to the scanning point is greater than the light intensity threshold, it means that the beam tracking is completed; otherwise, the beam tracking stage continues.

8. 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 comprises: The first optical communication device collects light 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 phase according to the first feedback information; if so, generates scanning information and sends it to the second optical communication device; if not, continues to communicate according to the current beam link; The second optical communication device receives the scanning information, selects a scanning point with a maximum total photon count value based on the scanning information, generates second feedback information according to the scanning point, and sends the second feedback information to the first optical communication device; The first optical communication device receives the second feedback information, obtains an optimal scanning point, and controls the light beam of the first optical communication device to point to the optimal scanning point.

9. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 8, 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 a frame header and a light intensity check result bit; The scanning information includes a frame header, a beam tracking stage bit, a scanning point sequence number bit and a light intensity check bit; The second feedback information includes a frame header, a beam tracking result bit, and an optimal scanning point sequence number bit.

10. The beam tracking method for underwater wireless optical communication based on photon counting according to claim 8, characterized in that: The first optical communication device or the second optical communication device comprises a control chip, and a transmitting module and a receiving module connected to the control chip at the same time; The transmitting module includes a laser and a piezoelectric ceramic deflection mirror, and both the laser and the piezoelectric ceramic deflection mirror are connected to the control chip; wherein the piezoelectric ceramic deflection mirror is used to adjust the direction of the laser beam emitted by the laser; The emission module comprises a single-photon detector and a beam-shrinking mirror, a filter is arranged between the single-photon detector and the beam-shrinking mirror, and the single-photon detector is connected to the control chip.

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