Space laser communication optical axis control device and method

Abstract

The invention provides a space laser communication optical axis control device and method, a first-stage fine tracking loop uses a photoelectric detector to cooperate with a fast reflector 1, a second-stage fine tracking loop uses a nutation assembly to cooperate with a fast reflector 2, and the tracking zero position of the first-stage fine tracking loop is corrected according to the offset of a second-stage fast reflector. The light beam control system is applied to space laser communication, and through cooperation of the two stages of fine tracking loops, the light beam control system has the advantage of being capable of restraining light beam jitter caused by high frequency and strong vibration and has the advantage of compensating deviation of a communication optical axis and a tracking optical axis in real time.

Description

Technical Field

[0001] The invention belongs to the technical field of optical equipment, and specifically relates to a device and method for controlling an optical axis of space laser communication. Background Art

[0002] my country regards the construction of satellite Internet as a new infrastructure and steadily promotes the networking of satellite constellations. An important part of constellation networking is the establishment and maintenance of inter-satellite communication links. There are two ways to implement inter-satellite communication links: microwave communication and laser communication. Compared with microwave communication, laser communication has unique advantages, namely low power consumption, high speed, small size, no spectrum resource restrictions, and good confidentiality. Laser communication links will become an indispensable part of satellite constellations.

[0003] In order to achieve intersatellite laser communication, it is necessary to first establish and maintain the link through a scanning capture and tracking device, that is, to efficiently couple the space light into the optical fiber, and then modulate and demodulate the optical signal. The laser communication link is affected by the micro-vibration and thermal deformation of the satellite platform, resulting in a decrease in the coupling efficiency of the space light to the optical fiber. The existing conventional solution uses a single-stage precision tracking device to achieve control of the optical axis, but this design is limited by the limited bandwidth of the precision tracking loop. In a strong space vibration environment, the coupling efficiency of the space light to the optical fiber is reduced. In addition, due to the separate design of the tracking axis and the communication axis, the optical system is periodically affected by the thermal environment of the space and thermally deforms. During the long-term maintenance of the communication link, the tracking axis and the communication axis are not coaxial. In order to solve the problem of limited bandwidth of a single-stage precision tracking loop, a two-stage precision tracking device is introduced in High-speed free-space optical communication using standard fiber communication components without optical amplification [J]. Advanced Photonics Nexus, 2023, 2(6): 065001. DOI: 10.1117 / 1.APN.2.6.065001. However, this design fails to solve the problem of non-coaxiality between the tracking optical axis and the communication optical axis caused by thermal deformation of the optical system. The patent with authorization announcement number: CN114389683B applied by Beijing Remote Sensing Equipment Research Institute on March 29, 2024, introduces a method for autonomous correction of the optimal tracking point of a communication detector on orbit, but this method fails to solve the problem of separation of the tracking axis and the communication axis, and this method actively causes the signal light coupling power to decrease during the scanning process, increasing the risk of communication link termination. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a space laser communication optical axis control device, which uses a first-stage fine tracking loop using a photodetector in combination with a fast reflector, and a second-stage fine tracking loop using a nutation assembly in combination with a fast reflector, and at the same time corrects the tracking zero position of the first-stage fine tracking loop according to the offset of the second-stage fast reflector. The present invention is applied to space laser communication, and the coordination of the two-stage fine tracking loop enables the beam control system to have the advantage of suppressing beam jitter caused by high frequency and strong vibration, and also has the advantage of real-time compensation for the deviation between the communication optical axis and the tracking optical axis.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, the present invention provides a space laser communication optical axis control device, which is characterized in that it includes a first-level precision tracking loop, a second-level precision tracking loop and a signal processing and control board;

[0007] The first-stage fine tracking loop includes a signal light that is reflected by a first fast reflector and then reaches a beam splitter, and after being reflected by the beam splitter, is converged into a light spot 1 on a first photodetector through a first lens group;

[0008] The second-stage fine tracking loop includes the signal light being reflected by the first fast reflector and then reaching the beam splitter, being transmitted by the beam splitter, passing through the second fast reflector, and then converging into a light spot 2 on the nutating component through the second lens group, spatial light coupling into the optical fiber, and then passing through the optical fiber beam splitter and part of the light entering the second photodetector;

[0009] The signal processing and control board is respectively connected to the first fast reflector, the first photodetector, the second fast reflector, the nutation assembly and the second photodetector by electrical signals;

[0010] By adjusting the positions of the beam splitter, the first photodetector, the second fast reflector and the nutation assembly, the initial zero position of the light spot on the first photodetector and the second photodetector, and the initial zero position driving voltage value of the first fast reflector and the second fast reflector are set;

[0011] The driving voltage values ​​are all output by the signal processing and control board, and the light spot positions are all processed and analyzed by the signal processing and control board.

[0012] On the other hand, the present invention also provides a control method for the above-mentioned space laser communication optical axis control device, which is characterized in that it includes the steps of:

[0013] S1. Determine the initial zero position of the light spot 1 on the first photodetector and the initial zero position driving voltage value of the first fast reflector; determine the initial zero position of the light spot 2 on the nutation assembly and the initial zero position driving voltage value of the second fast reflector;

[0014] S2. After the signal light is reflected by the first fast reflector and the beam splitter, it is converged into a light spot 1 on the first photodetector through the first lens group. The signal processing and control board obtains the current position of the light spot 1, and calculates the position deviation of the light spot 1 according to the initial zero position of the light spot 1 on the first photodetector;

[0015] S3. According to the position deviation of the light spot 1 obtained in step S2, the first fast reflector is adjusted so that the position of the light spot 1 converges to the initial zero position of the light spot 1;

[0016] S4. Control the nutation assembly to swing according to a specific trajectory, preferably the swing trajectory is circular, optionally the swing trajectory is a cross;

[0017] S5. The signal light is reflected by the first fast reflector and reaches the beam splitter. After being transmitted by the beam splitter, the signal light passes through the second fast reflector and converges into a light spot 2 on the nutating assembly through the second lens group. After that, part of the light passes through the optical fiber beam splitter and enters the second photodetector. The signal processing and control board obtains the current position of the light spot 2 and calculates the position deviation of the light spot 2 according to the initial zero position of the light spot 2 on the nutating assembly.

[0018] S6. According to the position deviation of the light spot 2 obtained in step S5, adjust the second fast reflector so that the position of the light spot 2 converges to the initial zero position of the light spot 2;

[0019] S7. Sliding statistics of the average driving voltage of the second fast reflection mirror, and calculating the deviation between the average driving voltage of the second fast reflection mirror and the initial zero driving voltage value of the second fast reflection mirror, when the deviation is greater than the set threshold, the zero value of the light spot 1 on the first photodetector is corrected;

[0020] S8. Execute steps S2-S3 again to make the position of the light spot 1 converge to the corrected zero position value of the light spot 1 until the entire workflow is terminated.

[0021] Furthermore, in step S7, the deviation (ΔnFVX2, ΔnFVY2) between the average driving voltage of the second fast reflection mirror and the initial zero driving voltage value of the second fast reflection mirror is calculated, and the formula is as follows:

[0022]

[0023] In the formula, The average value of the X-axis driving voltage of the second fast reflector calculated for the nth slide, The average Y-axis driving voltage of the second fast reflector calculated for the nth slide, FVX 21 FVY is the X-axis zero position driving voltage value of the second fast reflection mirror, 21 is the Y-axis zero position driving voltage value of the second fast reflecting mirror;

[0024] In step S7, the zero position value of the light spot 1 on the first photodetector is corrected according to the following formula:

[0025]

[0026] Where A is the conversion matrix from the deviation of the second fast reflector driving voltage to the zero position correction of spot 1, Xt 1(m-1) Yt is the zero position X-axis coordinate value of spot 1 after m-1 corrections, 1(m-1) is the Y-axis coordinate value of the zero position of spot 1 after the m-1th correction, Xt1 is the X-axis coordinate value of the zero position of spot 1 after the m-1th correction, and Yt1 is the Y-axis coordinate value of the zero position of spot 1 after the m-1th correction.

[0027] Compared with the prior art, the present invention has the following beneficial effects: the two-stage precision tracking loop proposed in the invention not only improves the beam disturbance suppression capability of the entire beam control system, but also solves the problem of real-time compensation of the communication optical axis and the tracking optical axis, thereby ensuring the long-term maintenance of the space laser communication link.

[0028] By precisely controlling each component in the optical path, precise control of the laser communication optical axis is achieved, thus ensuring the stability and efficiency of communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of the optical axis control device for space laser communication of the present invention.

[0030] Figure 2 Flow chart of the control method of the present invention DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but this should not limit the protection scope of the present invention.

[0032] See also Figure 1 , Figure 1The structure diagram of the space laser communication optical axis control device of the present invention is shown in the figure. A space laser communication optical axis control device includes a signal processing and control board 1, a first fast-transmitting mirror 2, a beam splitter 3, a first lens group 4, a first photodetector 5, a second fast-transmitting mirror 6, a second lens group 7, a nutation assembly 8, an optical fiber beam splitter 9, and a second photodetector 10. The incident light is reflected by the first fast-reflecting mirror 2 and reaches the beam splitter 3. A part of the light is reflected by the beam splitter 3 and converged by the first lens group 4 and irradiated on the first photodetector 5; a part of the light is transmitted through the beam splitter 3 and then passes through the second fast-reflecting mirror 6 and the second lens group 7 and converges on the nutation assembly 8, and then passes through the optical fiber beam splitter 9, and a part of the light enters the second photodetector 10. The first fast-reflecting mirror 2, the first photodetector 5, the second fast-reflecting mirror 6, the nutation assembly 8, and the second photodetector 10 are all electrically connected to the signal processing and control board 1.

[0033] When the space laser communication optical axis control system is installed and adjusted, the beam splitter 3, the first photoelectric detector 5, the second fast reflector 6, and the nutation assembly 8 are adjusted, and the initial zero position of the light spot 1 on the first photoelectric detector is (Xt 11 , Yt 11 ), where Xt 11 is the initial zero position X-axis coordinate value of the light spot 1 on the first photodetector, Yt 11 is the initial zero position Y-axis coordinate value of the light spot 1 on the first photodetector; at this time, the initial zero position driving voltage value of the first fast reflector is (FV×t 11 ,FV 11 ), where FVXt 11 FVYt is the initial zero position driving voltage value of the first fast reflector X axis, 11 is the initial zero position driving voltage value of the Y axis of the first fast reflector; at this time, the zero position of the light spot 2 on the nutation assembly is (Xt 21 , Yt 21 ), where Xt 21 Yt is the zero position X-axis coordinate value of spot 2 on the nutation assembly, 21 is the zero position Y-axis coordinate value of the light spot 2 on the nutation assembly; at this time, the zero position driving voltage value of the second fast reflector is (FVXt 21 ,FV 21 ), where FVXt 21 FVYt is the X-axis zero position driving voltage value of the second fast reflector, 21 is the zero-position driving voltage value of the second fast reflector Y axis. The above driving voltage values ​​are all output by the signal processing and control board, and the light spot positions are all processed and analyzed by the signal processing and control board.

[0034] Based on the structure of the space laser communication optical axis control system, the control method of the system is now introduced. Figure 2 As shown, the specific implementation steps are as follows:

[0035] Step 1: The signal processing and control board sets the initial zero voltage value of the first fast reflector (FVXt 11 ,FV 11 ), where FVXt 11 FVYt is the initial zero position driving voltage value of the first fast reflector X axis, 11 is the initial zero position driving voltage value of the Y axis of the first fast reflection mirror; the zero position driving voltage value of the second fast reflection mirror (FVXt 21 ,FV 21 ), where FVX 21 FVY is the X-axis zero position driving voltage value of the second fast reflection mirror, 21 is the Y-axis zero position driving voltage value of the second fast reflecting mirror;

[0036] Step 2: After the signal light is reflected by the first fast reflector and the beam splitter, it is converged into a light spot 1 on the first photodetector through the first lens group, and the signal processing and control board calculates the current coordinate value of the light spot 1;

[0037] Step 3: The signal processing and control board card calculates the current coordinate value of the spot 1 and the initial zero position (Xt 11 , Yt 11 ) to obtain the position deviation of spot 1, where Xt 11 is the initial zero position X-axis coordinate value of the light spot 1 on the first photodetector, Yt 11 is the initial zero position Y-axis coordinate value of the light spot 1 on the first photodetector;

[0038] Step 4: The signal processing and control board calculates the control signal of the first fast reflector according to the position deviation of the light spot 1 in step 3, and outputs it to the first fast reflector, so that the position of the light spot 1 converges to the initial zero position (Xt 11 , Yt 11 ), where Xt 11 is the initial zero position X-axis coordinate value of the light spot 1 on the first photodetector, Yt 11 is the initial zero position Y-axis coordinate value of the light spot 1 on the first photodetector;

[0039] Step 5: The signal processing and control board controls the nutation assembly to swing along a specific trajectory. The preferred swing trajectory is circular, and the optional swing trajectory is cross-shaped.

[0040] Step 6: After the signal light passes through the first fast reflector, the beam splitter, and the second fast reflector, it converges into a light spot 2 on the nutating assembly through the first lens group. At this time, the spatial light is coupled into the optical fiber, and then part of the light passes through the optical fiber beam splitter and enters the second photodetector. The signal processing and control board calculates the current position coordinate value of the light spot 2 (Xp 2k , Yp 2k ), where Xp 2k The kth calculation of the X-axis coordinate value of the spot 2 position, Yp 2k Calculate the Y-axis coordinate value of the light spot 2 position for the kth time;

[0041] Step 7: The signal processing and control board card calculates the current coordinate value of the spot 2 (Xp 2k , Yp 2k ) and the initial zero position (Xt 21 , Yt 21 ), calculate the position deviation of spot 2 (ΔX 2k , ΔY 2k ), where Xt 21 Yt is the initial zero position X-axis coordinate value of spot 2 on the nutation assembly, 21 is the initial zero Y-axis coordinate value of spot 2 on the nutation assembly, ΔX 2k The kth calculation of the X-axis deviation of the spot 2 position, ΔY 2k Calculate the Y-axis deviation of the spot 2 position for the kth time. The calculation formula is as follows:

[0042] ΔX 2k =Xp 2k -Xt 21

[0043] ΔY 2k =Yp 2k -Yt 21

[0044] Step 8: The signal processing and control board calculates the control signal of the second fast reflector according to the position deviation of the light spot 2 in step 7, and outputs it to the second fast reflector, so that the position of the light spot 2 converges to the zero position (Xt 21 , Yt 21 ), where Xt 21 Yt is the zero position X-axis coordinate value of spot 2 on the nutation assembly, 21 is the zero position Y-axis coordinate value of the light spot 2 on the nutation assembly;

[0045] Step 9: The signal processing and control board slides and counts the average value of the driving voltage of the second fast reflector ,in is the average value of the X-axis driving voltage of the second fast reflector calculated for the n-th sliding, and nFVYt2 is the average value of the Y-axis driving voltage of the second fast reflector calculated for the n-th sliding;

[0046] Step 10: The signal processing and control board obtains the deviation (ΔnFVX2, ΔnFVY2) between the average driving voltage of the second fast reflection mirror calculated in step 9 and the zero-position driving voltage value of the second fast reflection mirror, wherein ΔnFVX2 is the deviation between the average driving voltage of the second fast reflection mirror X-axis and the zero-position driving voltage value, and ΔnFVY2 is the deviation between the average driving voltage of the second fast reflection mirror Y-axis and the zero-position driving voltage value. The calculation formula is as follows:

[0047]

[0048] in The average value of the X-axis driving voltage of the second fast reflector calculated for the nth slide, The average Y-axis driving voltage of the second fast reflector calculated for the nth slide, FVX 21 FVY is the X-axis zero position driving voltage value of the second fast reflection mirror, 21 is the Y-axis zero position driving voltage value of the second fast reflecting mirror;

[0049] Step 11: When the deviation of the second fast reflector driving voltage obtained in step 10 is greater than the threshold, the zero position value of the light spot 1 on the first photodetector is corrected to (Xt 1m , Yt 1m ), where Xt 1m Yt is the X-axis coordinate value of the zero position of spot 1 after the mth correction, 11 is the Y-axis coordinate value of the zero position of spot 1 after the mth correction. The calculation formula for zero position correction is as follows

[0050]

[0051] Where A is the conversion matrix from the deviation of the second fast reflector driving voltage to the zero position correction of spot 1, Xt 1(m-1) Yt is the zero position X-axis coordinate value of spot 1 after the m-1th correction, 11 is the Y-axis coordinate value of the zero position of spot 1 after the m-1th correction;

[0052] Step 12: Execute steps 2 to 4, so that the position of the light spot 1 converges to the corrected zero position value.

Claims

1. A space laser communication optical axis control device, characterized in that: It includes a first-level precision tracking loop, a second-level precision tracking loop, and a signal processing and control board; The first-stage fine tracking loop includes a signal light that is reflected by a first fast reflector and then reaches a beam splitter, and after being reflected by the beam splitter, is converged into a light spot 1 on a first photodetector through a first lens group; The second-stage fine tracking loop includes the signal light being reflected by the first fast reflector and then reaching the beam splitter, being transmitted by the beam splitter, passing through the second fast reflector, and then converging into a light spot 2 on the nutating component through the second lens group, spatial light coupling into the optical fiber, and then passing through the optical fiber beam splitter and part of the light entering the second photodetector; The signal processing and control board is respectively connected to the first fast reflector, the first photodetector, the second fast reflector, the nutation assembly and the second photodetector by electrical signals; By adjusting the positions of the beam splitter, the first photodetector, the second fast reflector and the nutation assembly, the initial zero position of the light spot on the first photodetector and the second photodetector, and the initial zero position driving voltage value of the first fast reflector and the second fast reflector are set; The driving voltage values ​​are all output by the signal processing and control board, and the light spot positions are all processed and analyzed by the signal processing and control board.

2. The control method of the space laser communication optical axis control device according to claim 1, characterized in that: Includes steps: S1. Determine the initial zero position of the light spot 1 on the first photodetector and the initial zero position driving voltage value of the first fast reflector; determine the initial zero position of the light spot 2 on the nutation assembly and the initial zero position driving voltage value of the second fast reflector; S2. After the signal light is reflected by the first fast reflector and the beam splitter, it is converged into a light spot 1 on the first photodetector through the first lens group. The signal processing and control board obtains the current position of the light spot 1, and calculates the position deviation of the light spot 1 according to the initial zero position of the light spot 1 on the first photodetector; S3. According to the position deviation of the light spot 1 obtained in step S2, the first fast reflector is adjusted so that the position of the light spot 1 converges to the initial zero position of the light spot 1; S4. Control the nutation assembly to swing according to a specific trajectory, preferably the swing trajectory is circular, optionally the swing trajectory is a cross; S5. The signal light is reflected by the first fast reflector and reaches the beam splitter. After being transmitted by the beam splitter, the signal light passes through the second fast reflector and converges into a light spot 2 on the nutating assembly through the second lens group. After that, part of the light passes through the optical fiber beam splitter and enters the second photodetector. The signal processing and control board obtains the current position of the light spot 2 and calculates the position deviation of the light spot 2 according to the initial zero position of the light spot 2 on the nutating assembly. S6. According to the position deviation of the light spot 2 obtained in step S5, adjust the second fast reflector so that the position of the light spot 2 converges to the initial zero position of the light spot 2; S7. Sliding statistics of the average driving voltage of the second fast reflection mirror, and calculating the deviation between the average driving voltage of the second fast reflection mirror and the initial zero driving voltage value of the second fast reflection mirror, when the deviation is greater than the set threshold, the zero value of the light spot 1 on the first photodetector is corrected; S8. Execute steps S2-S3 again to make the position of the light spot 1 converge to the corrected zero position value of the light spot 1 until the entire workflow is terminated.

3. The control method of the space laser communication optical axis control device according to claim 2, characterized in that: In step S7, the deviation (ΔnFVX2, ΔnFVY2) between the average driving voltage of the second fast reflection mirror and the initial zero driving voltage value of the second fast reflection mirror is calculated, and the formula is as follows: In the formula, The average value of the X-axis driving voltage of the second fast reflector calculated for the nth slide, The average Y-axis driving voltage of the second fast reflector calculated for the nth slide, FVX 21 FVY is the X-axis zero position driving voltage value of the second fast reflection mirror, 21 is the Y-axis zero position driving voltage value of the second fast reflecting mirror; In step S7, the zero position value of the light spot 1 on the first photodetector is corrected according to the following formula: Where A is the conversion matrix from the deviation of the second fast reflector driving voltage to the zero position correction of spot 1, Xt 1(m-1) Yt is the zero position X-axis coordinate value of spot 1 after m-1 corrections, 1(m-1) is the Y-axis coordinate value of the zero position of spot 1 after the m-1th correction, Xt1 is the X-axis coordinate value of the zero position of spot 1 after the m-1th correction, and Yt1 is the Y-axis coordinate value of the zero position of spot 1 after the m-1th correction.

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