Unmanned aerial vehicle wireless light transmission method and system

Abstract

The invention discloses a wireless light transmission method for an unmanned aerial vehicle. The wireless light transmission method comprises the following steps: S100, adopting an LD light source with a tail fiber as a signal source to send a signal at a sending end; s200, when the system tracks and aligns, a variable-focus optical fiber collimator of an optical fiber light outlet is rotated and / or rotated to adjust, zooming is achieved, the light emitting angle of a light source is changed, and then the system adapts to signal transmission of different distances and different angles; s300, taking a large-view-field MPPC array as optical signal receiving equipment at a receiving end, and calling a built-in multi-array-element channel combined likelihood receiving algorithm for receiving based on the jittering of the unmanned aerial vehicle in the receiving process; the invention further discloses an unmanned aerial vehicle wireless light transmission system. According to the technical scheme, alignment control is more flexible, a tracking system is simpler and more convenient, convergence, collimation and divergence of light velocity are achieved, different communication requirements of high-speed communication, long-distance communication and large-angle communication are met, efficient receiving of an unmanned aerial vehicle optical communication system is achieved, and the performance of long-distance outdoor optical communication is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless optical transmission for unmanned aerial vehicles, and in particular to a wireless optical transmission method and system for unmanned aerial vehicles. Background Art

[0002] At present, the communication methods for UAV flight control, communication, and image transmission mainly include wireless communication links, networked UAVs (using 5G communication networks), audio and video encoding and decoding technologies, and IP video data stream transmission technologies. These communication methods jointly ensure the efficiency and reliability of UAV flight control, data transmission, and real-time image transmission.

[0003] Currently, the main frequency bands for drone flight control, communication, and image transmission are in the relatively mature traditional GHz radio wave bands such as 0.84, 1.43, and 2.4.

[0004] However, factors such as the complex electromagnetic space environment and strong electromagnetic interference in cities can easily limit the flight control, communication, image transmission and other applications of drones based on the traditional radio GHz frequency band. In addition, the GHz frequency band signals of traditional drone communications are extremely susceptible to malicious attacks, interference, deception and theft by other radio equipment, causing drone safety accidents. Summary of the invention

[0005] The main purpose of the present invention is to propose a wireless optical transmission method and system for unmanned aerial vehicles, aiming to solve the technical problem that existing unmanned aerial vehicles are difficult to perform electromagnetically compatible, reliable and high-speed communication transmission in complex electromagnetic environments such as strict electromagnetic control and strong electromagnetic interference.

[0006] To achieve the above object, the wireless optical transmission method for unmanned aerial vehicles proposed in the present invention comprises the following steps: S100: At the transmitting end, an LD light source with a pigtail is used as a signal source to send signals; S200: When the system is tracking and aligning, the variable focus optical fiber collimator at the optical fiber outlet is rotated and / or rotated to achieve zooming, change the light emitting angle of the light source, and thus adapt to signal transmission at different distances and angles; S300: A large-field-of-view MPPC array is used as the optical signal receiving device at the receiving end. During the receiving process, based on the jitter of the drone, the built-in joint likelihood receiving algorithm of the multi-element channel is called for reception.

[0007] Optionally, in step S100, the LD light source is connected to the optical fiber through a fixed-focus optical fiber collimator, and the light outlet of the optical fiber is connected to the variable-focus optical fiber collimator to achieve connection and send signals.

[0008] Optionally, in step S200, the LD light source and its driving module may be fixed, and only the optical fiber end connected to the variable-focus optical fiber collimator needs to be controlled to perform rotating beam tracking and align with the receiving end.

[0009] Optionally, in step S200, the variable focus fiber collimator can be regarded as a convex lens, and by adjusting the position of the convex lens, light convergence, collimation, and divergence can be achieved to meet different communication requirements of high-speed communication, long-distance communication, and large-angle communication.

[0010] Optionally, in step S300, the influence of outdoor long-distance atmospheric turbulence on drone jitter and pointing error is taken into account. By jointly analyzing the atmospheric turbulence and pointing error, the weak light detection capability of the MPPC array is utilized at the receiving end of the communication link to associate the array channels, and call the joint likelihood algorithm of the multi-element channels to ensure the receiving capability.

[0011] A wireless optical transmission system for an unmanned aerial vehicle comprises a transmitting end and a receiving end, wherein the transmitting end comprises an LD light source with a pigtail, an optical fiber, a fixed-focus optical fiber collimator and a variable-focus optical fiber collimator, wherein the LD light source is connected to the optical fiber through the fixed-focus optical fiber collimator, wherein an end of the optical fiber away from the fixed-focus optical fiber collimator is provided with a light outlet, wherein the variable-focus optical fiber collimator is rotatably connected to the optical fiber through the light outlet, wherein an end of the variable-focus optical fiber collimator away from the light outlet is aligned with the receiving end, wherein the receiving end is received by an MPPC array, wherein the MPPC array is provided with a built-in receiving module, wherein the receiving module is provided with an array joint likelihood receiving algorithm.

[0012] Optionally, the LD light source has a built-in driving module.

[0013] Optionally, the MPPC array is a multi-channel receiving plane of 4×4 array elements.

[0014] The technical solution of the present invention has the following beneficial effects: (1) At the transmitting end of the communication link, it is proposed to use an LD light source with a pigtail as the signal source, and a variable focus fiber collimator design is used at the light outlet of the optical fiber. When aligning the communication optical link, it is only necessary to control the rotation of the fiber collimator to achieve light beam alignment, without controlling the overall rotation of the transmitting end. The alignment control is more flexible and the tracking system is simpler. The fiber collimator adopts a variable focus design. By controlling the position of the lens inside the collimator, the convergence, collimation and divergence of light speed can be achieved, which can adapt to different communication needs such as high-speed communication, long-distance communication and large-angle communication.

[0015] (2) Taking into account the influence of atmospheric turbulence and pointing errors in outdoor long-distance environments, the weak light detection capability of the MPPC array is utilized at the receiving end of the communication link to associate the array channels. A joint likelihood algorithm for multi-element channels is proposed to achieve efficient reception of the UAV optical communication system, significantly improving the performance of long-distance outdoor optical communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in 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 only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the process steps of a wireless optical transmission method for a drone according to an embodiment of the present invention; Figure 2 This is a schematic structural diagram of a transmitting light source system of a wireless optical transmission system for an unmanned aerial vehicle according to an embodiment of the present invention; Figure 3 A schematic diagram of adjusting a variable-focus optical fiber collimator of a UAV combined with a UAV wireless optical transmission system according to an embodiment of the present invention; Figure 4 A schematic diagram of a pointing deviation of an array received optical signal caused by drone jitter in a drone wireless optical transmission system according to an embodiment of the present invention; Figure 5 A schematic diagram of BER of a JML receiving system of a wireless optical transmission system for a drone under different pointing error values ​​according to an embodiment of the present invention; Figure 6 A schematic diagram of BER of JML and ML reception under different SNRs of a wireless optical transmission system for unmanned aerial vehicles according to an embodiment of the present invention; Figure 7 The figure is a schematic diagram of SNR gain of JML reception and ML reception under different pointing errors of a wireless optical transmission system for an unmanned aerial vehicle according to an embodiment of the present invention.

[0018] It should be noted that: Figure 5 The horizontal axis Pt is the optical power, and the vertical axis BER is the bit error rate; Figure 6 The horizontal axis SNR is the signal-to-noise ratio, the vertical axis BER is the bit error rate, mrad is the unit of measurement, milliradian, ML is the maximum likelihood, and JML is the maximum joint likelihood; Figure 7The horizontal axis is the number of receiving channels, and the vertical axis SNR gain is the signal-to-noise ratio gain.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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 are within the scope of protection of the present invention.

[0021] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] The present invention provides a wireless optical transmission method and system for unmanned aerial vehicles.

[0024] like Figure 1 As shown, in one embodiment of the present invention, the wireless optical transmission method of the unmanned aerial vehicle comprises the following steps: S100: At the transmitting end, an LD light source with a pigtail is used as a signal source to send signals; S200: When the system is tracking and aligning, the variable focus optical fiber collimator at the optical fiber outlet is rotated and / or rotated to achieve zooming, change the light emitting angle of the light source, and thus adapt to signal transmission at different distances and angles; S300: A large-field-of-view MPPC array is used as the optical signal receiving device at the receiving end. During the receiving process, based on the jitter of the drone, the built-in joint likelihood receiving algorithm of the multi-element channel is called for reception.

[0025] Specifically, in step S100, the LD light source is connected to the optical fiber through a fixed-focus optical fiber collimator, and the light outlet of the optical fiber is connected to the variable-focus optical fiber collimator to achieve connection and send signals.

[0026] Specifically, in step S200, the LD light source and its driving module may be fixed, and only the optical fiber end connected to the variable-focus optical fiber collimator needs to be controlled to perform rotating beam tracking and align with the receiving end.

[0027] Specifically, in step S200, the variable focus fiber collimator can be regarded as a convex lens, and by adjusting the position of the convex lens, the convergence, collimation and divergence of light can be achieved to meet different communication requirements of high-speed communication, long-distance communication and large-angle communication.

[0028] Specifically, in step S300, the influence of outdoor long-distance atmospheric turbulence on drone jitter and pointing error is taken into account. Through joint analysis of atmospheric turbulence and pointing error, the weak light detection capability of the MPPC array is used at the receiving end of the communication link to associate the array channels and call the joint likelihood algorithm of the multi-element channels to ensure the receiving capability.

[0029] like Figure 2 As shown, on the other hand, the present invention also proposes a wireless optical transmission system for unmanned aerial vehicles to implement the above method. The system includes a transmitting end and a receiving end. The transmitting end includes an LD light source 100 with a pigtail, an optical fiber, a fixed-focus optical fiber collimator 200, and a variable-focus optical fiber collimator 300. The LD light source 100 has a built-in driving module. The LD light source 100 is connected to the optical fiber through the fixed-focus optical fiber collimator 200. The light outlet of the optical fiber is connected to the variable-focus optical fiber collimator 300. The variable-focus optical fiber collimator 300 is connected to one end of the optical fiber. Figure 3 As shown, it can be equivalent to a convex lens. By adjusting the position of the convex lens, the convergence, collimation and divergence of light can be achieved to meet different communication needs such as high-speed communication, long-distance communication and large-angle communication. When the LD light source system with pigtail is tracking the beam, the LD light source 100 and its driving module can be fixed. Only the optical fiber end connected to the variable focus optical fiber collimator 300 needs to be controlled to perform rotating beam tracking and align with the receiving end. The control is more flexible. The LD light source 100 is connected to the optical fiber through the fixed focus optical fiber collimator 200. The end of the optical fiber away from the fixed focus optical fiber collimator 200 is provided with a light outlet. The variable focus optical fiber collimator 300 can be rotatably connected to the optical fiber through the light outlet. The end of the variable focus optical fiber collimator 300 away from the light outlet is aligned with the receiving end. The receiving end is received by the MPPC array. The MPPC array is a multi-channel receiving plane with 4×4 array elements. The MPPC array has a built-in receiving module. The receiving module has a built-in array joint likelihood receiving algorithm. The MPPC array with a large field of view is used to receive optical signals. Based on the jitter of the drone, an array joint likelihood receiving algorithm is proposed to effectively improve the receiving capability of the system.

[0030] Considering the pointing error caused by the jitter of the drone, such as Figure 4 As shown, in the unmanned optical communication system based on MPPC array reception, Indicates the communication distance between Tx (transmitter) and Rx (receiver). represents the pointing error angle, and Represents the receiving angle of MPPC. MPPC is a multi-channel receiving plane with 4×4 array elements. Figure 4 As shown in the figure, the solid line with double-ended arrows is the angle between the two dotted lines. When the optical signal is transmitted between Tx-Rx through the lens, it is affected by the jitter of the UAV (drone), and the lens focuses the optical signal onto the receiving surface of the MPPC.

[0031] The signal received by the drone optical communication link at Rx is expressed as: ; In the formula, is the channel coefficient, To send data, is the noise of each channel. Since the duration of signal reception is very short compared to the jitter time of the drone, the channel Constant within a data transmission cycle. These transmitters do not consider signal interference and are set to complete all data transmission within the communication cycle. Set the transmission data to , the length is , the training data is set to , and the received data is , and the total data received is In the In the channel, To send a signal, Indicates that the received signal is "1", and It indicates that the received signal is "0". is the total noise received by each channel of MPPC. The noise of the channels can be expressed as zero mean and variance Modeling.

[0032] UAV optical communication channel attenuation The channel attenuation is mainly affected by atmospheric turbulence attenuation and pointing error. It can be expressed as: ; in, is the Meijer-G function, is the Gamma function, is the ratio between the equivalent beam radius of the detection surface at Rx and the pointing error, is the amplitude of the received power, is the deterministic channel attenuation loss, and are the effective values ​​of large-scale and small-scale turbulent eddies, respectively, which are expressed as: ; in, , is the wave number, is the atmospheric refractive index parameter, is the optical communication distance (Tx-Rx).

[0033] In outdoor UAV optical communication systems, the light beam will fluctuate due to the random jitter of the UAV's wings, which in turn affects the position of the light beam in the receiving plane.

[0034] like Figure 3 As shown, If it is larger than the receiver's FOV, communication will be interrupted. and are two independent random variables, represented on the coordinate axes of the detection surface and The pointing deviation is assumed to be The random variable of the pointing error is expressed as: ; In drone systems Tends to be stable and random, a channel in the receive plane is represented as follows: ; In the In the channels, the given atmospheric path is , transmission digital signal, and the received data signal The length is Under the condition of , its PDF is expressed as: ; Assume that a beam reaches each channel of the MPPC array at the receiving end, and the amplitude of the received signal is , then we get The likelihood function of a received signal is: ; Maximum Likelihood (ML) Estimator of From the ML equation The likelihood estimate of the magnitude is given. pass Calculated. When the channel receives a signal When , the likelihood function is expressed as: ; Assume the likelihood ratio acceptance threshold is , the threshold can be obtained from the following relationship: When, the judgment ;when When, the judgment After simplification, we get: ; According to the above conclusions, when the signal Replaced by Then, the test statistic Follows a Gaussian discrete random signal. Therefore, the decision probability is: ; ; in, is the power SNR when the signal amplitude is the maximum likelihood estimate.

[0035] By studying and analyzing BER performance, we can optimize system design and adjust parameter configuration to improve system reliability and performance stability. BER will PDF of channel status To evaluate ; From the SNR given above, we can derive: ; According to the Meijer-G function The transformation is rewritten as the above function: ; Substituting the Meijer-G transfer function of SNR and the above formula, we can get: ; According to the Meijer-G function formula, it can be deduced that: ; Finally, according to BER, we can conclude: ; The receiving simulation parameters are set, and the anti-turbulence attenuation and anti-jitter performance of the proposed multi-channel maximum joint likelihood (JML) receiving scheme are simulated. By changing the transmission power of the light source and the arc value of the pointing error, the BER distribution of the receiver under different conditions can be observed, and the communication performance under different receiving conditions can be compared. It should be noted that in order to ensure the fairness of the data reception experiment, the pointing errors of the drone jitter in ML reception and multi-channel JML reception are the same and equal, and are within the acceptable range of the detector. The receiving simulation parameter settings used by the drone wireless optical communication system are shown in Table 1: Table 1 ; like Figure 5 As shown in the figure, through simulation, it can be found that when the UAV carries a wireless optical communication system and there is a pointing error in the movement, the horizontal axis represents different optical powers, and the vertical axis represents the JML receiving BER of MPPC under different jitter errors. ) condition, with the increase of optical power ( ), the change of BER. The figure can be used to analyze the impact of UAV pointing error on the performance of UAV optical communication system. As the optical power increases from -5 dBm to positive values, the BER under various pointing error conditions decreases. As the pointing error increases, that is, the influence of UAV jitter increases, the BER shows an overall upward trend. This is because a larger pointing error leads to a decrease in the performance of the received signal. Especially under lower optical power conditions, the increase in BER is more obvious. Under a pointing error of 4 mrad, even under higher optical power conditions, the BER is higher than the BER under a pointing error of 1 mrad. In the UAV optical communication system, by adjusting the power of the transmitting light source, the negative impact of the pointing error caused by jitter on the communication performance can be effectively offset. When the optical signal is within the MPPC receiving FOV, it can be observed that as the jitter error increases, the BER curve gradually tends to be horizontal. This is due to the fluctuation of the pointing error caused by the UAV jitter. If the pointing error exceeds the range of the MPPC receiving FOV, the communication will be interrupted.

[0036] like Figure 6 As shown, under different pointing errors ( , ) and analyzed the performance of JML reception and traditional ML reception. Figure 6 It can be seen from the figure that the receiving performance of JML and ML is compared under the conditions of 1mrad and 3mrad pointing errors. Under the conditions of pointing error and SNR, the performance of JML reception is significantly better than that of ML reception, and JML can receive signals more effectively. When the pointing error increases from 1mrad to 3mrad, it can be seen that the performance of JML reception is slightly improved, while the performance of ML reception is reduced. This shows that larger pointing errors have little effect on JML reception, but are more sensitive to ML reception. This is because ML reception relies more on precise pointing alignment when processing signals. With the increase of SNR, both receiving performances show an improving trend, especially JML reception. In summary, JML receiving technology can show higher receiving performance when processing signals in the UAV optical communication system, especially under the conditions of lower pointing error and high SNR.

[0037] It should be noted that Figure 6In the figure, "solid line + solid triangle" is used to represent 1mrad-ML, "solid line + solid hexagon" is used to represent 1mrad-JML, "dotted line + hollow square" is used to represent 3mrad-ML, and "dotted line + solid hexagon" is used to represent 3mrad-JML. Among them, the "dotted line + hollow square" representation method may cause the hollow square to be filled with the solid line part of the dotted line due to the unequal distance between the connecting lines of adjacent squares, and then the hollow square or solid square will be randomly presented in the figure.

[0038] like Figure 7 As shown in the figure, the simulation results show that with different numbers of receiving channels, the pointing errors of 1mrad and 3mrad ( , ). As the number of receiving channels increases, the receiving performance improves. By increasing the number of receiving channels, the signal receiving capability of the UAV optical communication system can be effectively improved, thereby improving the SNR. By comparing the receiving performance of ML and ML, under the same conditions, the performance of JML is usually higher than that of ML. This is because JML reception is more effective in processing multi-channel signals and pointing errors. When faced with a pointing error of 3mrad, JML achieved a received SNR gain of 1mrad higher than ML, which shows the advantage of JML's multi-channel reception. In summary, using the JML reception method to increase the number of receiving channels can effectively improve the receiving performance of the UAV optical communication system in the presence of pointing errors.

[0039] It should be noted that: Figure 5 The horizontal axis Pt is the optical power, and the vertical axis BER is the bit error rate; Figure 6 The horizontal axis SNR is the signal-to-noise ratio, the vertical axis BER is the bit error rate, mrad is the unit of measurement, milliradian, ML is the maximum likelihood, and JML is the maximum joint likelihood; Figure 7 The horizontal axis is the number of receiving channels, and the vertical axis SNR gain is the signal-to-noise ratio gain.

[0040] The specific principles of the present invention are as follows: 1. The communication link of drones needs to use radio resources. At present, the spectrum used by drones in the world is mainly concentrated in UHF, L and C bands, and other frequency bands are also scattered. The Radio Management Bureau of the Ministry of Industry and Information Technology of my country has initially formulated the "Use of Frequency of Drone Systems", planning the 840.5-845MHz, 1430-1444MHz and 2408-2440MHz frequency bands for unmanned aircraft systems. When drones are deployed in urban areas, frequency bands below 1442MHz should be used. 3. The 2408~1440MHz frequency band can be used for the downlink of drone systems. When the radio station is working, it shall not affect other legal radio services, nor seek radio interference protection. Generally speaking, VHF, UHF, L and S bands are more suitable for low-cost short-range drone line-of-sight links; X and Ku bands are suitable for medium-range and long-range drone line-of-sight links and air relay links; Ku and Ka bands are suitable for medium- and long-range satellite relay links.

[0041] Networked drones, that is, using 5G communication networks to connect and control drones. This method provides a wider coverage range than Wi-Fi or Bluetooth, making drone communication more flexible and reliable. The 5G communication method for drones mainly provides a high-quality 5G communication environment for drone data transmission through the planning of 5G network architecture and the introduction of 5G airborne terminals. 5G network technology provides a variety of advantages for drone applications, including the use of large-scale multi-antenna technology, new spectrum (such as C-band, millimeter wave band), new coding (such as Polar code, LDPC code), new frame structure and flexible Numerology. The application of these technologies enhances the efficiency and reliability of drone communications. Specifically, 5G's large-scale multi-antenna technology accurately aligns the service drones and ground terminals with narrower beams, enhances useful signals and reduces interference within and between cells, thereby improving low-altitude coverage capabilities. In terms of application, 5G drones have played an important role in power grid transmission line equipment inspection, operator macro station equipment inspection, traffic management and land-air coordination, emergency communications and rescue. For example, in power grid inspections, 5G drones can conduct 360-degree all-round high-definition video inspections, providing 4K or even 8K clarity, which is sufficient to view all details of the equipment, while also completing data collection and archiving. In addition, 5G drones can also carry special pods to perform special treatments under low-latency and precise operations, such as drone flamethrower obstacle removal. Audio and video codec technology and IP video data stream transmission technology are also key to drone communication. Audio and video codec technology can process the compression and decompression of digital video, so that video signals can be effectively transmitted on the network. IP video data stream transmission technology is responsible for transmitting these encoded and decoded audio and video signals over long distances through the network, usually using 3G / 4G wireless networks to ensure video transmission with a certain clarity.

[0042] 2. Explanation of terms: LD: Laser Diode, laser diode; MPPC: Multi-Pixel Photon Counter, silicon photomultiplier tube; SNR: Signal to Noise Ratio, signal to noise ratio; ML: Maximum Likelihood, maximum likelihood; JML: Joint Maximum Likelihood, maximum joint likelihood; FOV: Field of View, field of view; PDF:Probability Density Function,Probability density function; SNR: Signal to Noise Ratio, signal to noise ratio; BER: Bit Error Rate, bit error rate; UAV: Unmanned Aerial Vehicle.

[0043] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A wireless optical transmission method for unmanned aerial vehicles, characterized in that: The following steps are involved: S100: At the transmitting end, an LD light source with a pigtail is used as a signal source to send signals; S200: When the system is tracking and aligning, the variable focus optical fiber collimator at the optical fiber outlet is rotated and / or rotated to achieve zooming, change the light emitting angle of the light source, and thus adapt to signal transmission at different distances and angles; S300: A large-field-of-view MPPC array is used as the optical signal receiving device at the receiving end. During the receiving process, based on the jitter of the drone, the built-in joint likelihood receiving algorithm of the multi-element channel is called for reception.

2. The wireless optical transmission method for unmanned aerial vehicles according to claim 1, characterized in that: In the step S100, the LD light source is connected to the optical fiber through a fixed-focus optical fiber collimator, and the light outlet of the optical fiber is connected to the variable-focus optical fiber collimator to achieve connection and send signals.

3. The wireless optical transmission method for unmanned aerial vehicles according to claim 1, characterized in that: In the step S200, the LD light source and its driving module are fixed, and the optical fiber end connected to the variable-focus optical fiber collimator is controlled to perform rotating beam tracking and align with the receiving end.

4. The wireless optical transmission method for unmanned aerial vehicles according to claim 1, characterized in that: In step S200, the variable focus optical fiber collimator can be regarded as a convex lens. By adjusting the position of the convex lens, the convergence, collimation and divergence of light can be achieved to meet different communication requirements of high-speed communication, long-distance communication and large-angle communication.

5. The wireless optical transmission method for unmanned aerial vehicles according to claim 1, characterized in that: In step S300, the influence of outdoor long-distance atmospheric turbulence on drone jitter and pointing error is taken into consideration. By jointly analyzing the atmospheric turbulence and pointing error, the weak light detection capability of the MPPC array is utilized at the receiving end of the communication link to associate the array channels and call the joint likelihood algorithm of the multi-element channels to ensure the receiving capability.

6. A UAV wireless optical transmission system, implementing the UAV wireless optical transmission method according to any one of claims 1 to 5, characterized in that: It comprises a transmitting end and a receiving end, wherein the transmitting end comprises an LD light source with a pigtail, an optical fiber, a fixed-focus optical fiber collimator and a variable-focus optical fiber collimator, the LD light source is connected to the optical fiber through the fixed-focus optical fiber collimator, the end of the optical fiber away from the fixed-focus optical fiber collimator is provided with a light outlet, the variable-focus optical fiber collimator is rotatably connected to the optical fiber through the light outlet, the end of the variable-focus optical fiber collimator away from the light outlet is aligned with the receiving end, the receiving end is received by an MPPC array, the MPPC array is provided with a built-in receiving module, and the receiving module has a built-in array joint likelihood receiving algorithm.

7. The UAV wireless optical transmission system according to claim 6, characterized in that: The LD light source has a built-in driving module.

8. The UAV wireless optical transmission system according to claim 6, characterized in that: The MPPC array is a multi-channel receiving plane with 4×4 array elements.

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