Laser bidirectional detection system based on adaptive adjustment of specific gravity spectrometer

Abstract

The present application relates to the field of laser communication, and particularly relates to a laser bidirectional detection system based on adaptive adjustment of light splitting ratio, comprising a transceiving common optical unit, an adjustable light splitting unit, a transmitting link unit, a receiving link unit and an intelligent control unit; the receiving link unit is used for receiving downlink laser; the transceiving common optical unit is used for realizing common aperture coupling and polarization state conversion of uplink laser and downlink laser; the adjustable light splitting unit is used for dynamically adjusting energy distribution ratio between uplink laser and downlink laser; the intelligent control unit is used for extracting and analyzing link state parameters of downlink laser, and deciding optimal energy distribution ratio between uplink laser and downlink laser; wherein, the link state parameters comprise received optical power, flicker index, background noise and bit error rate. The present application can realize dynamic optimal distribution of transceiving energy, significantly improve stability and availability of laser link under complex weather such as haze, turbulence and strong light interference, and has small volume, fast response and controllable cost.

Description

Technical Field

[0001] This invention belongs to the field of laser communication technology, and particularly relates to a laser bidirectional detection system based on adaptive adjustment of beam splitting ratio. Background Technology

[0002] In air-to-air and air-to-ground laser bidirectional communication links, atmospheric channels exhibit time-varying characteristics. For example, under weather conditions such as fog, haze, rain, and snow, atmospheric attenuation is severe, requiring the system to have higher transmission power to penetrate the channel. In strong turbulence or clear weather, the asymmetry of uplink and downlink spot drift and scintillation effects may cause signal overload at one end and weak signal at the other, severely affecting communication quality.

[0003] Currently, existing laser bidirectional detection systems typically employ fixed-splitting-ratio optical structures (such as 50:50 beam splitters) to achieve a common-aperture design for both transmitter and receiver. While such systems can operate normally in laboratory environments or under stable weather conditions, they present the following problems in practical applications: First, a fixed splitting ratio cannot adapt to dynamic weather changes. Under attenuating weather conditions such as fog, haze, rain, and snow, the transmitted light power is insufficient to penetrate the channel, which can easily lead to link interruption or increased bit error rate. Under strong turbulence conditions, the asymmetric fading of uplink and downlink cannot be effectively compensated. Under strong background light interference (such as direct sunlight), the signal-to-noise ratio at the receiver drops sharply, and the detector is prone to saturation or signal submersion.

[0004] Secondly, while existing technologies using polarization isolation or circulators can achieve transmit-receive isolation, their isolation level is fixed and the energy ratio of the transmitted and received light cannot be independently adjusted. When it is necessary to increase the transmit power, the signal energy at the receiver will be weakened accordingly, and vice versa, making it difficult to independently optimize transmit-receive performance.

[0005] Furthermore, most existing laser bidirectional detection systems are open-loop designs, with the splitting ratio fixed at the factory or manually set once during installation, and cannot be adjusted subsequently. This makes the system unable to cope with sudden weather changes (such as aircraft passing through clouds or fog rising in valleys), and manual remote adjustment suffers from time delays and operational complexity, lacking autonomous optimization capabilities based on real-time link quality feedback.

[0006] Some existing technologies employ a dual-aperture design (separate transmission and reception), using independent adjustments to transmit power and receive gain to address weather changes. However, this approach suffers from drawbacks such as large size and weight, difficulty in optical axis alignment, poor long-term stability, and high cost, making it unsuitable for airborne or spaceborne platforms with stringent requirements for lightweight design and shared optical paths. Furthermore, while some existing technologies utilize tunable optical attenuators, these are mostly used only for coarse adjustment of transmit power or overload protection at the receiver, failing to establish an intelligent mapping relationship between weather type and transmit / receive splitting ratio. The system cannot autonomously determine whether the current weather is "attenuation-type" or "turbulent-type," thus hindering the adoption of targeted splitting strategies.

[0007] In summary, existing laser bidirectional detection systems have significant shortcomings in areas such as dynamic energy allocation between transmit and receive, isolation and allocation decoupling, closed-loop adaptive control, adaptability to extreme weather conditions, and intelligent decision-making capabilities. Therefore, there is an urgent need for an adaptive laser bidirectional detection system capable of dynamically adjusting the transmit-receive splitting ratio based on real-time weather conditions to achieve optimal energy allocation. Summary of the Invention

[0008] In view of this, the present invention aims to provide a laser bidirectional detection system based on adaptive adjustment of the splitting ratio, so as to achieve dynamic optimal allocation of transmit and receive energy, physical decoupling of transmit and receive isolation and energy allocation, closed-loop adaptive control, improved link stability under extreme weather conditions, and intelligent weather-splitting ratio mapping decision.

[0009] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A laser bidirectional detection system based on adaptive adjustment of spectral density includes: Transmit link unit, used to generate and modulate uplink laser; The receiving link unit is used to receive downlink laser signals; A shared optical unit for transmitting and receiving is used to achieve common-aperture coupling and polarization state conversion of uplink and downlink lasers; An adjustable beam splitter unit is used to dynamically adjust the energy distribution ratio between the uplink and downlink lasers; The intelligent control unit is used to extract and analyze the link status parameters of the downlink laser and determine the optimal energy allocation ratio between the uplink and downlink lasers. The link status parameters include received optical power, scintillation index, background noise, and bit error rate.

[0010] Furthermore, the adjustable beam splitter unit includes a half-wave plate, a servo turntable, and a polarizing beam splitter prism. The half-wave plate is mounted on the servo turntable. The upward-flowing laser is reflected by the polarizing beam splitter prism to form polarized reflected light, and the downward-flowing laser is transmitted through the polarizing beam splitter prism to form polarized transmitted light. The servo turntable drives the half-wave plate to rotate, changing the angles between the polarized reflected light and the polarized transmitted light and the principal axis of the polarizing beam splitter prism, thereby controlling the energy ratio of the polarized reflected light and the polarized transmitted light; or... The tunable beam splitting unit includes a MEMS micromirror array and a diffraction grating. The uplink or downlink laser is dispersed by the diffraction grating and then irradiates the MEMS micromirror array. By independently changing the flip angle of each micromirror in the MEMS micromirror array, the energy ratio between the uplink and downlink lasers can be controlled.

[0011] Furthermore, the shared optical unit for transmitting and receiving includes a primary mirror, a secondary mirror, a quarter-wave plate, and a first collimating lens group. The primary mirror and the secondary mirror constitute a common-aperture transmitting and receiving telescope. The quarter-wave plate is located between the first collimating lens group and the secondary mirror and is used to realize the mutual conversion between linearly polarized light and circularly polarized light. The first collimating lens group is used to expand and collimate the light beam.

[0012] Furthermore, the transmission link unit includes a laser and a second collimating lens group. The laser is used to emit uplink laser light, and the second collimating lens group is used to expand and collimate the uplink laser light beam.

[0013] Furthermore, the receiving link unit includes a converging lens group and a photodetector. The converging lens group is used to converge the downlink laser, and the photodetector is used to receive the downlink laser and perform photoelectric conversion.

[0014] Furthermore, the intelligent control unit includes a signal processor and a drive circuit. The signal processor is used to execute the meteorological classification decision algorithm, automatically determine the current meteorological type based on the link status parameters of the downlink laser, calculate the optimal energy distribution ratio between the uplink and downlink lasers, and control the servo turntable to rotate the half-wave plate to the target angle through the drive circuit or control each micromirror in the MEMS micromirror array to flip to the target angle through the drive circuit. The meteorological types include attenuated meteorological conditions, turbulent meteorological conditions, background light interference, and good meteorological conditions.

[0015] Furthermore, the decision logic of the meteorological classification decision algorithm includes: When the optical power received by the signal processor is lower than the power threshold and the received flicker index is higher than the flicker threshold, it is determined to be turbulent weather, and the energy allocation ratio is adjusted to the receiving priority mode. When the optical power received by the signal processor is lower than the power threshold and the scintillation index received by the signal processor is lower than or equal to the scintillation threshold, it is determined to be attenuation weather, and the energy allocation ratio is adjusted to the transmission priority working mode. When the optical power received by the signal processor is higher than or equal to the power threshold and the background noise received by the signal processor is higher than the noise threshold, it is determined to be background light interference, and the energy allocation ratio is adjusted to the receiving priority working mode. When the optical power received by the signal processor is higher than or equal to the power threshold and the background noise received by the signal processor is lower than or equal to the noise threshold, it is determined to be good weather and the balanced working mode is maintained.

[0016] Furthermore, the energy allocation ratio corresponding to the transmit priority mode is 80:20, the energy allocation ratio corresponding to the receive priority mode is 40:60 or 20:80, and the energy allocation ratio corresponding to the balanced mode is 50:50.

[0017] Furthermore, when the meteorological classification decision algorithm cannot determine the current meteorological type, a perturbation optimization mode is activated. The servo turntable is controlled by the drive circuit to rotate the half-wave plate by a preset step angle. The bit error rate is monitored in real time, and the rotation angle of the half-wave plate is continuously adjusted in the direction of reducing the bit error rate until the bit error rate is minimized. Alternatively, the flip angle of each micromirror in the MEMS micromirror array is controlled by the drive circuit. The bit error rate is monitored in real time, and the flip angle of the micromirror is continuously adjusted in the direction of reducing the bit error rate until the bit error rate is minimized.

[0018] Furthermore, the intelligent control unit also includes a remote communication interface for bidirectional communication with the signal processor, used to receive external manual intervention commands. The execution priority of the manual intervention commands is higher than the automatic decision of the signal processor. The manual intervention commands include forcibly setting the energy distribution ratio between the uplink laser and the downlink laser, locking the current working mode, and switching to any working mode.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects: 1. Achieve dynamic optimal allocation of transmit and receive energy, significantly improving link stability.

[0020] This invention introduces an adjustable beam splitting unit composed of a rotating half-wave plate and a polarizing beam splitter prism, enabling continuous and dynamic adjustment of the uplink and downlink laser energy distribution ratio within the range of 0% to 100% based on real-time meteorological conditions and link status parameters. Under attenuating weather conditions such as fog, rain, and snow, the system automatically increases the proportion of the uplink laser to enhance penetration; under strong background light interference, it automatically increases the proportion of the downlink laser to improve the signal-to-noise ratio; and under strong turbulence conditions, it automatically balances the proportions of the uplink and downlink lasers to suppress scintillation fading. Compared to existing technologies with fixed splitting ratios, this invention improves the availability of bidirectional laser links under complex weather conditions to over 98.5%, and reduces the bit error rate by 1 to 4 orders of magnitude.

[0021] 2. Achieve physical decoupling of transmit / receive isolation and energy distribution, enabling independent optimization of transmit and receive performance.

[0022] This invention employs a combination of a polarizing beam splitter prism and a half-wave plate to independently control the energy ratio of reflected light (transmitter) and transmitted light (receiver) by changing the polarization direction of the incident light. This design decouples transmit / receive isolation from energy distribution: when increased transmit power is needed, the reflectivity can be increased independently without weakening the receiving optical path; when increased receive sensitivity is needed, the transmittance can be increased independently without affecting transmit power. In contrast, existing polarization isolation or circulator solutions have fixed isolation levels and cannot independently adjust the transmit / receive energy ratio. This invention truly achieves flexible "transmit-priority" or "receive-priority" configurations, adapting to asymmetric link requirements.

[0023] 3. Construct a closed-loop adaptive control mechanism to achieve millisecond-level real-time response.

[0024] This invention constructs a complete closed-loop adaptive control mechanism of "perception-decision-execution-feedback". It monitors received link status parameters in real time using a photoelectric detector, automatically determines the current weather type and calculates the optimal energy allocation ratio using a meteorological classification decision algorithm built into the intelligent control unit, and uses a servo motor to drive the rotation of a half-wave plate to complete the adjustment within milliseconds. The adjusted link quality is then fed back to the intelligent control unit, forming a closed-loop optimization. Compared to existing open-loop systems or manual remote adjustment schemes, this invention can respond to sudden weather changes (such as aircraft passing through clouds or fog rising in valleys) in real time, with a response speed improved to within 100ms, significantly enhancing the system's adaptive capability to dynamic channels.

[0025] 4. Establish a meteorological-spectrum ratio intelligent mapping decision-making system with autonomous cognitive capabilities.

[0026] This invention proposes for the first time a splitting ratio decision logic based on meteorological classification. It can automatically identify attenuating weather conditions, turbulent weather conditions, background light interference, and favorable weather conditions based on a judgment threshold, and execute the corresponding energy allocation strategy. When the meteorological classification cannot be clearly defined, the system initiates a perturbation optimization mode, fine-tuning the rotation angle of the half-wave plate with a small step angle, monitoring the bit error rate trend in real time, and automatically locking in the optimal splitting ratio. This intelligent decision-making system enables the system to have autonomous learning and optimization capabilities, without relying on external weather forecasts or manual intervention, significantly improving the robustness of the laser link in unknown or changing environments.

[0027] 5. Achieves independent dual-path adjustment within a compact single-aperture structure, resulting in small size, light weight, and controllable cost.

[0028] This invention employs a shared-aperture design for both transmit and receive, requiring only the addition of an adjustable beam splitter module to an existing optical system to achieve the flexibility typically found only in traditional dual-aperture systems. Compared to existing dual-aperture solutions (separate transmit and receive), this invention avoids a significant increase in size and weight, eliminates the need for additional optical axis alignment and calibration, exhibits excellent long-term stability, and is suitable for airborne, spaceborne, and vehicle-mounted platforms with high requirements for lightweight design and shared optical path. Furthermore, the core components are all mature industrial products, increasing costs by approximately 2000-5000 RMB, offering high cost-effectiveness and significant engineering application value.

[0029] 6. Retain the manual remote intervention interface to balance intelligence and controllability.

[0030] Building upon automatic control, this invention also retains a remote human intervention channel, receiving remote commands via data link, satellite communication, or fiber optics. Human commands have the highest priority, supporting forced setting of energy allocation ratios, locking the current operating mode, or switching to any operating mode. This design not only meets the needs of unattended intelligent operation in daily life but also addresses the requirements for manual takeover in sudden extreme situations or special tasks, enhancing the system's security and flexibility. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This invention provides a schematic diagram of the structure of the laser bidirectional detection system based on adaptive adjustment of spectral density as described in Embodiment 1 of the present invention. Figure 2 A schematic diagram of the beam splitting principle of the tunable beam splitting unit described in Embodiment 1 of the present invention; Figure 3 A schematic flowchart of the closed-loop adaptive control method described in Embodiment 1 of the present invention.

[0032] Explanation of reference numerals in the attached diagram: 1. Transceiver shared optical unit; 11. Primary mirror; 12. Secondary mirror; 13. Quarter-wave plate; 14. First collimating lens group; 2. Adjustable beam splitting unit; 21. Half-wave plate; 22. Polarizing beam splitter prism; 23. Servo turntable; 3. Transmitting link unit; 3. Laser; 31. Second collimating lens group; 32. Reflector; 33. Receiving link unit; 4. Converging lens group; 41. Photodetector; 42. Intelligent control unit; 5. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0036] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "assembly," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0038] Example 1 like Figure 1 As shown, this embodiment 1 provides a laser bidirectional detection system based on adaptive adjustment of the splitting ratio, comprising five functional units, namely: The transceiver shared optical unit 1 includes a primary mirror 11, a secondary mirror 12, a quarter-wave plate 13, and a first collimating lens group 14. The primary mirror 11 and secondary mirror 12 are coaxially arranged, forming a Cassegrain telescope with a common aperture, used to emit laser light (i.e., uplink laser) and receive laser light from far-field targets (i.e., downlink laser). The quarter-wave plate 13 is positioned between the collimating lens group 14 and the secondary mirror 12 to achieve laser polarization state conversion. When receiving laser light, it converts the originally circularly polarized downlink laser light into linearly polarized light; when emitting laser light, it converts the originally linearly polarized uplink laser light into circularly polarized light. The first collimating lens group 14 expands and collimates the uplink or downlink laser light.

[0039] Adjustable beam splitting unit 2 includes a half-wave plate 21, a polarizing beam splitter prism 22, and a servo turntable 23. The servo turntable 23 includes a servo motor and a rotating platform. The servo motor drives the rotating platform to rotate. The half-wave plate 21 is mounted on the rotating platform, and the rotation angle of the half-wave plate 21 is controlled by the servo motor. The polarizing beam splitter prism 22 is positioned in the emission direction of the half-wave plate 21. The beam splitting surface of the polarizing beam splitter prism 22 is coated with a dielectric film, exhibiting reflectivity (>99%) for S-polarized light and transmittance (>99%) for P-polarized light. One incident surface of the polarizing beam splitter prism 22 serves simultaneously as the reflection input end of the uplink laser and the transmission output end of the downlink laser, while the opposite side serves as a common port for coupling with the half-wave plate 21.

[0040] Transmission link unit 3 includes a laser 31 and a second collimating lens group 32. The laser 31 outputs linearly polarized light as an uplink laser, and its polarization direction is consistent with the S-polarization direction of the polarizing beam splitter 22 (i.e., perpendicular to the incident plane). The second collimating lens group 32 is used to expand and collimate the linearly polarized light output by the laser 31 into parallel light. After the polarization direction is adjusted by the half-wave plate 21, the light is incident on the reflection input end of the polarizing beam splitter 22, and then reflected by a mirror 33 to the first collimating lens group 14.

[0041] The receiving link unit 4 includes a converging lens group 41 and a photodetector 42. The converging lens group 41 is used to converge the downlink laser output from the transmission output end of the polarizing beam splitter 22 onto the photosensitive surface of the photodetector 42. The photodetector 42 uses an avalanche photodiode (APD) or a PIN photodiode to convert the optical signal into an electrical signal.

[0042] The intelligent control unit 5 includes a signal processor and a drive circuit. The signal processor executes the meteorological classification decision algorithm, automatically determines the current weather type based on the link status parameters of the downlink laser, calculates the optimal energy distribution ratio between the uplink and downlink lasers, and controls the rotation angle of the servo motor through the drive circuit to rotate the half-wave plate 21 to the target angle. The weather types include attenuated weather, turbulent weather, background light interference, and good weather.

[0043] The intelligent control unit 5 also includes a remote communication interface for bidirectional communication with the signal processor, used to receive external manual intervention commands. The execution priority of the manual intervention commands is higher than the automatic decision of the signal processor. The manual intervention commands include forcibly setting the energy distribution ratio between the uplink laser and the downlink laser, locking the current working mode, and switching to any working mode.

[0044] The laser bidirectional detection system consists of a transmitting optical path and a receiving optical path: The emitted light path is as follows: The linearly polarized light (denoted as S-polarized light) emitted by the laser 31 is collimated by the second collimating lens group 32 and then incident on the half-wave plate 21. The half-wave plate 21 rotates the polarization direction of the incident S-polarized light by an angle of 2θ, converting it into linearly polarized light with a polarization direction that makes an angle of (90°-2θ) with the principal axis of the polarizing beam splitter 22. This linearly polarized light is then collimated by the first collimating lens group 14, converted into circularly polarized light by the quarter-wave plate 13, and finally reflected by the secondary mirror 12 and the primary mirror 11 before being emitted to the far-field target.

[0045] Receiving optical path: Downward circularly polarized light (rotation direction opposite to the emitted upward laser) emitted from the far-field target is reflected by the primary mirror 11 and secondary mirror 12, and then incident on the quarter-wave plate 13. The quarter-wave plate 13 converts the light into linearly polarized light, with its polarization direction perpendicular to the emitted linear polarization direction (i.e., becoming P-polarized). This P-polarized light is collimated by the first collimating lens group 14 and then incident on the half-wave plate 21, where it is rotated again by an angle of 2θ, becoming linearly polarized light with a polarization direction at an angle θ to the principal axis of the polarizing beam splitter 22. When this pre-polarized light is incident on the polarizing beam splitter 22, its P-polarized component is transmitted and converged by the converging lens group 41 onto the photodetector 42, converting the optical signal into an electrical signal.

[0046] like Figure 2 As shown, the adjustable beam splitter 2 is the core of this invention for achieving dynamic energy allocation for transmission and reception. Its working principle is based on polarization optics principles: Let the total power of the linearly polarized light incident on the half-wave plate 21 be... The polarization direction of the linearly polarized light makes an angle θ with the principal axis of the polarizing beam splitter 22. After passing through the half-wave plate 21, the polarization direction of the output linearly polarized light is rotated to an angle of 2θ with the principal axis of the polarizing beam splitter 22. When this linearly polarized light enters the polarizing beam splitter 22, its S-polarization component (perpendicular to the incident plane) is reflected, and its P-polarization component (parallel to the incident plane) is transmitted. According to Malus's law, the reflected light power (the power reflected back to the transmitting light path) is... And transmitted light power (power transmitted to the receiving optical path) They respectively satisfy: ; .

[0047] Therefore, by precisely controlling the angle θ of the servo motor rotating the half-wave plate 21, the splitting ratio can be continuously adjusted within the range of 0% to 100%. For example, when θ = 0°, the reflected energy is 100%, and the system operates in pure emission mode; when θ = 45°, the reflected energy and transmitted energy are each 50%, and the system operates in balanced mode; when θ = 90°, the transmitted energy is 100%, and the system operates in pure reception mode. Different θ angles are preset for different meteorological conditions, as shown in Table 1.

[0048] Table 1 Correspondence between Working Modes and Energy Allocation Ratios

[0049] The laser bidirectional detection system does not rely on external weather forecasts, but instead makes autonomous decisions based on the link state parameters of the downlink laser received in real time, forming a closed-loop control: The photodetector acquires data in real time → the signal processor extracts link status parameters → the intelligent decision-making calculates the optimal energy distribution ratio → the servo motor drives the adjustment of the half-wave plate rotation angle → the link quality is optimized → the data is returned for monitoring.

[0050] Link state parameters include: Received optical power: used to reflect the total link attenuation; Scintillation index: used to reflect the intensity of turbulence; Background noise: used to reflect the degree of external light interference; Bit error rate: Used to reflect the quality of communication.

[0051] In this embodiment 1, the intelligent control unit 5 has a built-in meteorological classification decision algorithm, which automatically determines the current meteorological type based on the monitored link status parameters and executes the corresponding energy allocation ratio strategy.

[0052] like Figure 3 The flowchart shown illustrates the closed-loop control method for dynamically adaptively adjusting the energy distribution ratio, which includes the following steps: S1: After the system is powered on, the signal processor controls the servo motor through the drive circuit to drive the half-wave plate to rotate to the initial position, i.e., θ=45°, so that the system works in the default 50:50 balanced mode.

[0053] S2: The signal processor reads real-time data from the photodetector at a predetermined sampling frequency and calculates the following link state parameters: received optical power. Scintillation Index Background noise .

[0054] S3: Signal processor judgment Is it below the power threshold? ;like Then further determine the flicker index. Is it higher than the preset flicker threshold? ;like If the weather is strong turbulent, the signal processor calculates the target θ=54.7° (corresponding to an energy allocation ratio of 40:60, with reception priority) according to Table 1 and generates a drive command; otherwise, if the weather is attenuated (such as fog, haze, rain, snow), the signal processor calculates the target θ=26.6° (corresponding to an energy allocation ratio of 80:20, with transmission priority) according to Table 1.

[0055] S4: If step S3 determines... Then the signal processor further determines the background noise. Is it higher than the preset noise threshold? ;like If the signal is strong, it is determined to be a strong background light interference. The signal processor calculates the target θ=63.4° according to Table 1 (corresponding to an energy distribution ratio of 20:80, with reception as the priority).

[0056] S5: If neither of the conditions in steps S3 and S4 are met, i.e. and If the weather is good, the system is considered to be in good condition. At this point, the system maintains the current θ=45°, or optionally activates a perturbation optimization mode. This perturbation optimization mode fine-tunes the rotation angle of the half-wave plate by adjusting the servo motor in small step angles (e.g., corresponding to a 0.5° change in θ angle) in either the forward or reverse direction. It also monitors the real-time trend of the bit error rate (BER) and continuously adjusts the BER rotation angle in the direction of decreasing BER until the BER angle that minimizes BER is found, which is then taken as the target θ angle.

[0057] S6: The signal processor converts the calculated target angle θ into the rotation steps and direction command of the servo motor, and drives the servo motor through the drive circuit to rotate the half-wave plate to the target angle. After completing one adjustment, the system delays for a short time (e.g., 10ms) to wait for the optical path to stabilize, and then returns to step S2 to start the next round of monitoring and adjustment cycle.

[0058] When the current weather type cannot be clearly determined (e.g., when all parameters are between the thresholds), the system activates the perturbation optimization mode to find the θ angle that minimizes the bit error rate.

[0059] To enhance system controllability, the intelligent control unit in this embodiment 1 also includes a remote communication interface for bidirectional communication with the signal processor, providing a channel for manual intervention. The operator sends commands via a ground station or remote terminal. Command types include "force setting energy distribution ratio," "lock current operating mode," and "switch to automatic mode." Upon receiving the command, the remote communication interface transmits it to the signal processor. The signal processor's internal program prioritizes manual commands. When a manual command is received, the automatic adjustment algorithm is paused, and the command is executed according to its content: if it is "force setting energy distribution ratio," the corresponding angle θ is directly sent to the drive circuit; if it is "lock current operating mode," automatic adjustment is paused, maintaining the current energy distribution ratio; if it is a "switch to automatic mode" command, closed-loop adaptive control is resumed.

[0060] Example 2 This embodiment 2 provides an alternative to the adjustable beam splitter module of embodiment 1. Unlike embodiment 1, the adjustable beam splitter module in this embodiment 2 uses a combination of MEMS micromirror array and diffraction grating to replace the half-wave plate and polarizing beam splitter prism.

[0061] Specifically, the tunable beam splitting module includes a diffraction grating and a MEMS micromirror array. The beam from the shared transceiver optical unit and the transmit link unit is first dispersed by the diffraction grating, with different wavelengths of light scattered onto different micromirrors in the MEMS micromirror array. Each micromirror can be independently flipped under the drive of a control circuit (integrated in the intelligent control unit). By precisely controlling the flip angle of each micromirror (e.g., ±12°), a specific wavelength or proportion of the beam can be reflected to the port of the receive link unit, while the remaining portion is reflected to the port of the transmit link unit, thereby achieving wavelength-selective or energy-programmable beam splitting.

[0062] The advantages of this alternative are its smaller size, chip-level integration capability, and polarization independence. Its disadvantages include lower optical power handling capacity (typically in the milliwatt range) and more complex control algorithms. This alternative is particularly suitable for micro-UAV platforms or on-chip optical interconnect scenarios with extreme constraints on size and weight.

[0063] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0064] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A laser bidirectional detection system based on adaptive adjustment of spectral density, characterized in that, include: Transmit link unit, used to generate and modulate uplink laser; The receiving link unit is used to receive downlink laser signals; A shared optical unit for transmitting and receiving is used to achieve common-aperture coupling and polarization state conversion of uplink and downlink lasers; An adjustable beam splitter unit is used to dynamically adjust the energy distribution ratio between the uplink and downlink lasers; The intelligent control unit is used to extract and analyze the link status parameters of the downlink laser and determine the optimal energy allocation ratio between the uplink and downlink lasers. The link status parameters include received optical power, scintillation index, background noise, and bit error rate.

2. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 1, characterized in that, The adjustable beam splitting unit includes a half-wave plate, a servo turntable, and a polarizing beam splitter prism. The half-wave plate is mounted on the servo turntable. The upward laser beam is reflected by the polarizing beam splitter prism to form polarized reflected light, and the downward laser beam is transmitted through the polarizing beam splitter prism to form polarized transmitted light. The servo turntable drives the half-wave plate to rotate, changing the angle between the polarized reflected light and the polarized transmitted light and the main axis of the polarizing beam splitter prism, thereby controlling the energy ratio of the polarized reflected light and the polarized transmitted light. or, The tunable beam splitting unit includes a MEMS micromirror array and a diffraction grating. The uplink or downlink laser is dispersed by the diffraction grating and then irradiates the MEMS micromirror array. By independently changing the flip angle of each micromirror in the MEMS micromirror array, the energy ratio between the uplink and downlink lasers can be controlled.

3. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 1, characterized in that, The shared optical unit for transmitting and receiving includes a primary mirror, a secondary mirror, a quarter-wave plate, and a first collimating lens group. The primary mirror and the secondary mirror constitute a common-aperture transmitting and receiving telescope. The quarter-wave plate is located between the first collimating lens group and the secondary mirror and is used to realize the mutual conversion between linearly polarized light and circularly polarized light. The first collimating lens group is used to expand and collimate the light beam.

4. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 1, characterized in that, The transmission link unit includes a laser and a second collimating lens group. The laser is used to emit uplink laser light, and the second collimating lens group is used to expand and collimate the uplink laser light beam.

5. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 1, characterized in that, The receiving link unit includes a converging lens group and a photodetector. The converging lens group is used to converge the downlink laser, and the photodetector is used to receive the downlink laser and perform photoelectric conversion.

6. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 2, characterized in that, The intelligent control unit includes a signal processor and a drive circuit. The signal processor is used to execute the meteorological classification decision algorithm, automatically determine the current meteorological type based on the link status parameters of the downlink laser, calculate the optimal energy distribution ratio between the uplink and downlink lasers, and control the servo turntable to rotate the half-wave plate to the target angle through the drive circuit or control each micromirror in the MEMS micromirror array to flip to the target angle through the drive circuit. The meteorological types include attenuated meteorological conditions, turbulent meteorological conditions, background light interference, and good meteorological conditions.

7. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 6, characterized in that, The decision logic of the meteorological classification algorithm includes: When the optical power received by the signal processor is lower than the power threshold and the received flicker index is higher than the flicker threshold, it is determined to be turbulent weather, and the energy allocation ratio is adjusted to the receiving priority mode. When the optical power received by the signal processor is lower than the power threshold and the scintillation index received by the signal processor is lower than or equal to the scintillation threshold, it is determined to be attenuation weather, and the energy allocation ratio is adjusted to the transmission priority working mode. When the optical power received by the signal processor is higher than or equal to the power threshold and the background noise received by the signal processor is higher than the noise threshold, it is determined to be background light interference, and the energy allocation ratio is adjusted to the receiving priority working mode. When the optical power received by the signal processor is higher than or equal to the power threshold and the background noise received by the signal processor is lower than or equal to the noise threshold, it is determined to be good weather and the balanced working mode is maintained.

8. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 7, characterized in that, The energy allocation ratio corresponding to the transmit priority mode is 80:20, the energy allocation ratio corresponding to the receive priority mode is 40:60 or 20:80, and the energy allocation ratio corresponding to the balanced mode is 50:

50.

9. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 7, characterized in that, When the meteorological classification decision algorithm cannot determine the current meteorological type, the perturbation optimization mode is activated. The servo turntable is controlled by the drive circuit to rotate the half-wave plate by a preset step angle. The bit error rate is monitored in real time, and the rotation angle of the half-wave plate is continuously adjusted in the direction of reducing the bit error rate until the bit error rate is minimized. Alternatively, the flip angle of each micromirror in the MEMS micromirror array is controlled by the drive circuit. The bit error rate is monitored in real time, and the flip angle of the micromirror is continuously adjusted in the direction of reducing the bit error rate until the bit error rate is minimized.

10. The laser bidirectional detection system based on adaptive adjustment of spectral density according to claim 7, characterized in that, The intelligent control unit also includes a remote communication interface for bidirectional communication with the signal processor, used to receive external manual intervention commands. The execution priority of the manual intervention commands is higher than the automatic decision of the signal processor. The manual intervention commands include forcibly setting the energy distribution ratio between the uplink laser and the downlink laser, locking the current working mode, and switching to any working mode.

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