Portable laser communication far field calibration source device and calibration method

Abstract

The embodiment of the specification provides a portable laser communication far field calibration source device and a calibration method, wherein the portable laser communication far field calibration source device comprises: a light source module, a double-wedge prism divergence angle adjusting module, a deformable mirror turbulence simulation module, a aspheric mirror collimation module, a visible light auxiliary alignment module and a control module. The continuous adjustment of the divergence angle is realized by the slope displacement of the double-wedge prism, and the field of view of the large-diameter receiving antenna is covered; the atmospheric turbulence effect is simulated by the deformable mirror to apply the wavefront phase distortion; the two-step alignment mode of the visible light coarse alignment combined with the energy feedback fine adjustment of the receiving end is used to realize the high-precision alignment without the closed-loop wavefront monitoring system. The application integrates the divergence angle adjusting, turbulence simulation and auxiliary alignment functions in one, and the whole machine is small in size, light in weight and convenient for on-site deployment, and can provide comprehensive integrated calibration test for the ground station of the satellite-ground laser communication and the solid laser communication terminal.

Description

Technical Field

[0001] The embodiments in this specification relate to the field of optical communication technology, and in particular to a portable laser communication far-field calibration source device. Background Technology

[0002] Space-to-ground laser communication is a key technology for achieving high-speed data transmission between satellites and ground stations. It boasts advantages such as high transmission rates, strong security, and small terminal size, and has become an important component of satellite internet and integrated space-air-ground information networks. Before deploying a space-to-ground laser communication system, thorough testing and verification of the communication terminals and ground stations on the ground are necessary to ensure reliable operation under real-world link conditions.

[0003] Existing laser communication calibration and testing technologies mainly include the following categories: Collimator method. Collimators are commonly used equipment for calibrating optical systems, and can generate collimated beams to simulate targets at infinity. However, traditional collimators have drawbacks such as fixed aperture, non-adjustable divergence angle, and inability to simulate turbulence. While large-aperture collimators can meet the testing requirements of large-aperture receiving antennas, they are bulky, heavy, and lack portability, and are also expensive, making rapid deployment in the field difficult.

[0004] A spatial light modulator turbulence simulator. Related technologies disclose atmospheric turbulence simulation devices based on spatial light modulators, which utilize a liquid crystal spatial light modulator to load a calculated phase screen to simulate turbulence effects. However, this type of scheme suffers from problems such as low refresh rate, limited phase modulation depth, and low light energy utilization, and it cannot adjust the divergence angle or simulate far-field target characteristics.

[0005] Deformable mirror turbulence simulator. Related technologies disclose atmospheric turbulence simulation devices based on deformable mirrors, which use the surface shape changes of deformable mirrors to simulate wavefront distortion. However, existing deformable mirror turbulence simulators only have the single function of turbulence simulation, lack the ability to adjust the divergence angle, cannot simulate the far-field divergence characteristics of satellite beacon light under different distances and scenarios, and do not integrate auxiliary alignment functions, making it difficult to meet comprehensive calibration requirements.

[0006] A dual-wedge prism adjustable collimator. Related technologies disclose a fiber optic collimator with continuously adjustable divergence angle, utilizing a combination of a fixed optical wedge and a moving optical wedge to achieve continuous adjustment of the output beam divergence angle. However, this scheme is only used for fiber optic collimators and does not address functions such as turbulence simulation, far-field calibration, and auxiliary alignment; it causes lateral deviation of the output beam during divergence angle adjustment, and no effective compensation method is provided; it also does not consider the coverage requirements of large-aperture receiving antennas and lacks integrated design with the alignment process of laser communication terminals.

[0007] Comprehensive analysis reveals the following shortcomings in existing technologies: There is a lack of integrated calibration equipment that combines divergence angle adjustment, turbulence simulation, and alignment assistance functions. Testers must use multiple independent devices to complete the entire calibration process, which is cumbersome and results in poor repeatability and positioning accuracy. Existing adjustable divergence angle solutions do not consider integration with the laser communication terminal alignment process and lack visible light-assisted alignment and energy feedback fine-tuning designs. Existing turbulence simulators lack quantitative control capabilities, making it difficult to accurately reproduce specific turbulence statistical characteristics. Furthermore, there is a lack of portable calibration sources suitable for rapid field deployment, making it difficult to cover the testing needs of large-aperture receiving antennas. Summary of the Invention

[0008] In view of this, embodiments of this specification provide a portable laser communication far-field calibration source device to address the technical deficiencies existing in the prior art.

[0009] According to a first aspect of the embodiments of this specification, a portable laser communication far-field calibration source device is provided, comprising: The light source module is used to generate laser light in the communication band. The double wedge prism divergence angle adjustment module is set after the light source module along the optical path. It includes a first wedge prism and a second wedge prism that can be translated along the inclined plane direction. The divergence angle of the emitted beam is adjusted by changing the inclined plane displacement of the second wedge prism. The deformable mirror turbulence simulation module is set after the double wedge prism divergence angle adjustment module along the optical path. It includes a deformable mirror and a high voltage amplifier. The deformable mirror receives a driving voltage to change the mirror surface shape and apply wavefront phase distortion to the beam to simulate atmospheric turbulence effects. The aspherical mirror collimation module is set after the deformable mirror turbulence simulation module along the optical path, and collimates the beam after divergence angle adjustment and turbulence simulation into a parallel beam or a beam with controllable divergence angle for emission. The visible light-assisted alignment module includes a visible light laser, in which the visible light emitted by the visible light laser is coaxial with the communication band laser emitted by the light source module, and is used to assist in coarse alignment; The control module communicates with the double wedge prism divergence angle adjustment module, the deformable mirror turbulence simulation module, and the visible light-assisted alignment module for unified and coordinated control.

[0010] In one possible implementation, the double wedge prism divergence angle adjustment module also includes a high-precision displacement slide and a slide driver. The second wedge prism is mounted on the high-precision displacement slide, which is driven by a piezoelectric ceramic or by a stepper motor in conjunction with a ball screw. The slide driver is connected to the control module to receive displacement commands and feedback the actual position.

[0011] In one possible implementation, the deformable mirror is a continuous surface piezoelectric deformable mirror, comprising a 61-unit piezoelectric actuator array arranged in a hexagonal pattern, with a mirror aperture of 25mm, coated with a broadband high reflectivity dielectric film, and the high voltage amplifier is a multi-channel high voltage amplifier, with each channel independently controllable, an output voltage range of 0 to 300V, and a resolution of not less than 12 bits.

[0012] In one possible implementation, the visible light laser in the visible light-assisted alignment module is a 532nm semiconductor-pumped solid-state laser. The visible light laser is fixed to the side of the device and is coaxially calibrated before leaving the factory to ensure that the visible light is coaxial with the output beam of the light source module.

[0013] In one possible implementation, the aspherical mirror collimation module includes an off-axis parabolic mirror made of silicon carbide, which has a reflectivity of not less than 98% in the operating wavelength range.

[0014] According to a second aspect of the embodiments of this specification, a calibration method is provided using the aforementioned portable laser communication far-field calibration source device, characterized by comprising the following steps: Place the portable laser communication far-field calibration source device in front of the laser communication terminal under test, fix it with a tripod and level it; Turn on the visible light-assisted alignment module, emit a visible reference beam, and adjust the overall attitude of the portable laser communication far-field calibration source device so that the visible light spot is located in the center area of ​​the receiving antenna of the laser communication terminal under test, thus completing the coarse alignment. Turn off the visible light-assisted alignment module, switch to the communication band laser emission of the light source module, turn on the optical power monitoring function of the laser communication terminal under test, and record the received optical power in real time. Using the coarse alignment position as the center, perform step scans on the portable laser communication far-field calibration source device or the laser communication terminal under test in the pitch and azimuth directions. Record the current received optical power with each step, and move the pointing position to the point of maximum received power to complete fine alignment. The control module sets the target divergence angle, and then uses the pre-stored calibration data to check the target displacement of the second wedge prism. The control module then drives the second wedge prism to move to the target position so that the divergence angle of the emitted beam covers the receiving field of view of the receiving antenna. The simulation scene parameters are set by the control module to generate a turbulent phase screen that conforms to Kolmogorov's statistical theory. The driving voltage sequence of the deformable mirror is calculated and applied to the deformable mirror to cause the deformable mirror to produce a corresponding surface shape change. Wavefront phase distortion is applied to the beam to simulate atmospheric turbulence effects. Turn on the scanning and capture mode of the laser communication terminal under test, turn on the output of the portable laser communication far-field calibration source device, record the time from the start of scanning to successful capture, repeat multiple times, and calculate the average capture time and capture success rate.

[0015] In one possible implementation, during the fine alignment step, the scanning step size is gradually reduced from 50 μrad to 5 μrad until the received power reaches a stable maximum value, and the received power at the final alignment position is recorded as the calibration reference.

[0016] In one possible implementation, the turbulent phase screen is generated using a power spectrum inversion method combined with subharmonic compensation, specifically including: Input the simulation scenario parameters, which include satellite orbital altitude, zenith angle, ground refractive index structure constant, and equivalent wind speed, and calculate the equivalent Fried parameter and equivalent Greenwood frequency. Frequency domain filtering was performed using a modified von Karman power spectrum, and the initial phase screen was obtained by inverse Fourier transform. Subharmonic sampling is performed in the low-frequency region to generate a compensated phase screen. The compensated phase screen is then superimposed on the initial phase screen to obtain the target phase screen. Verify the consistency between the phase structure function of the target phase screen and the theoretical value. If the deviation is less than 10%, the target phase screen is confirmed to be effective.

[0017] In one possible implementation, solving the driving voltage sequence includes: obtaining a pre-calibrated deformable mirror influence matrix, which is obtained by sequentially applying a unit voltage to each actuator and measuring the corresponding mirror deformation; using regularized least squares method to solve the driving voltage vector based on the target phase screen and the influence matrix, and improving the numerical stability of the driving voltage vector through singular value decomposition; and applying an open-loop surface change to the deformable mirror according to the solved driving voltage vector.

[0018] In one possible implementation, calibration data is obtained in advance through the following steps: a portable laser communication far-field calibration source device is fixed on a precision adjustment platform, the emitted beam is incident along the optical axis of a collimator, and a beam quality analyzer is installed at the focal plane of the collimator; the second wedge prism is moved to its initial position, the focal plane spot diameter is measured, and the current divergence angle is calculated; the second wedge prism is gradually moved from its initial position to its maximum stroke, and the actual divergence angle is repeatedly measured at each calibration point with a fixed step size, and the displacement and corresponding actual divergence angle of each calibration point are recorded; polynomial fitting is performed on the obtained discrete calibration data to establish an analytical relationship between the displacement and the divergence angle, and the fitted polynomial coefficients or the complete displacement-divergence angle lookup table are written into the firmware of the control module.

[0019] According to a third aspect of the embodiments of this specification, a computing device is provided, comprising: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions. When the computer-executable instructions are executed by the processor, they implement the steps of the portable laser communication far-field calibration source device described above.

[0020] According to a fourth aspect of the embodiments of this specification, a computer-readable storage medium is provided that stores computer-executable instructions, which, when executed by a processor, implement the steps of the portable laser communication far-field calibration source device described above.

[0021] According to a fifth aspect of the embodiments of this specification, a computer program is provided, wherein when the computer program is executed in a computer, it causes the computer to perform the steps of the portable laser communication far-field calibration source device described above.

[0022] This specification provides a portable laser communication far-field calibration source device and calibration method. The portable laser communication far-field calibration source device includes a light source module, a double-wedge prism divergence angle adjustment module, a deformable mirror turbulence simulation module, an aspherical mirror collimation module, a visible light-assisted alignment module, and a control module. Continuous adjustment of the divergence angle is achieved through the inclined plane displacement of the double-wedge prism, covering the field of view of a large-aperture receiving antenna. A deformable mirror is used to apply wavefront phase distortion to simulate atmospheric turbulence effects. A two-step alignment method combining visible light coarse alignment and receiver energy feedback fine adjustment is employed to achieve high-precision alignment without a closed-loop wavefront monitoring system. This application integrates divergence angle adjustment, turbulence simulation, and assisted alignment functions into one unit. The entire device is small in size, lightweight, and easy to deploy in the field, providing comprehensive calibration testing for ground stations and solid-state laser communication terminals. Attached Figure Description

[0023] Figure 1 This is a simplified structural diagram of a portable laser communication far-field calibration source device provided in one embodiment of this specification; Figure 2 This is a flowchart illustrating a calibration method provided in one embodiment of this specification; Figure 3 This is an overall schematic diagram of a portable laser communication far-field calibration source device provided in one embodiment of this specification. Detailed Implementation

[0024] Many specific details are set forth in the following description to provide a full understanding of this specification. However, this specification can be implemented in many other ways than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of this specification. Therefore, this specification is not limited to the specific implementations disclosed below.

[0025] The terminology used in one or more embodiments of this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the one or more embodiments of this specification. The singular forms “a” and “the” as used in one or more embodiments of this specification and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in one or more embodiments of this specification refers to and includes any or all possible combinations of one or more associated listed items.

[0026] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this specification, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this specification, and similarly, second may also be referred to as first. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0027] This specification provides a portable laser communication far-field calibration source device, which will be described in detail in the following embodiments.

[0028] See Figure 1 , Figure 1 This diagram illustrates a simplified structural schematic of a portable laser communication far-field calibration source device according to some embodiments of this specification. Specifically, it includes: a light source module for generating laser light in the communication band; a double-wedge prism divergence angle adjustment module, disposed along the optical path after the light source module, comprising a first wedge prism and a second wedge prism movable along the inclined plane direction, wherein the divergence angle of the emitted beam is adjusted by changing the inclined plane displacement of the second wedge prism; and a deformable mirror turbulence simulation module, disposed along the optical path after the double-wedge prism divergence angle adjustment module, comprising a deformable mirror and a high-voltage amplifier, wherein the deformable mirror receives a driving voltage to change the mirror... The beam consists of a surface-mount module that applies wavefront phase distortion to simulate atmospheric turbulence. An aspherical mirror collimation module, positioned after the deformable mirror turbulence simulation module along the optical path, collimates the beam after divergence angle adjustment and turbulence simulation into parallel light or a beam with a controllable divergence angle. A visible light-assisted alignment module, including a visible light laser, is coaxial with the communication band laser emitted by the light source module to assist in coarse alignment. A control module is communicatively connected to the double wedge prism divergence angle adjustment module, the deformable mirror turbulence simulation module, and the visible light-assisted alignment module for unified and coordinated control.

[0029] The light source module can refer to the functional unit responsible for generating communication band lasers for calibration. For example, this module uses a wavelength-tunable semiconductor laser with single-mode fiber output to provide a stable and reliable coherent light source for subsequent optical processing. Communication band lasers can refer to near-infrared lasers suitable for free-space optical communication, such as lasers with wavelengths covering the range of 1530 nm to 1570 nm. This band matches the operating band of the space-to-ground laser communication system and can accurately reflect the transmission characteristics of the communication link.

[0030] A double-wedge prism divergence angle adjustment module refers to an optical adjustment unit that changes the divergence angle of the emitted beam by varying the relative positions of two wedge prisms. For example, this module utilizes the effective optical thickness variation of a fixed wedge and a moving wedge combination to modulate the wavefront curvature, thereby achieving continuous adjustment of the divergence angle. The first wedge prism can refer to a wedge-shaped optical element fixedly installed in the optical path, its position remaining constant as a reference for divergence angle adjustment. The second wedge prism can refer to a wedge-shaped optical element mounted on a displacement mechanism, movable along its own inclined plane, adjusting the combined optical thickness by changing its relative position to the first wedge prism. The inclined plane displacement refers to the distance the second wedge prism moves along its inclined plane; this displacement directly determines the effective thickness of the overlapping area of ​​the two prisms, thereby controlling the magnitude of the divergence angle of the emitted beam.

[0031] A deformable mirror turbulence simulation module can refer to a functional unit that uses the surface shape changes of a deformable mirror to simulate wavefront distortion caused by atmospheric turbulence. For example, this module applies different voltages to each driver of the deformable mirror, causing the mirror surface to undergo spatial deformation consistent with the target turbulent phase screen, thereby applying corresponding phase modulation to the reflected beam. A deformable mirror can refer to a continuous surface mirror with multiple independent drivers, each driver independently controlling the displacement of a local area of ​​the mirror surface. The desired mirror surface shape is formed through the synergistic effect of the drivers. A high-voltage amplifier can refer to an electronic device that converts the low-voltage control signal output from the control module into the high-voltage signal required to drive the deformable mirror, used to drive each channel of the deformable mirror to operate independently. Wavefront phase distortion refers to the deviation of the beam wavefront in spatial distribution from an ideal plane wave, such as the phase fluctuations caused by the optical path difference due to atmospheric turbulence. Applying this distortion to the beam can simulate real atmospheric propagation conditions.

[0032] An aspherical mirror collimation module refers to an optical unit that uses an aspherical mirror to convert a diverging beam into a parallel beam or a beam with a specific divergence angle. For example, this module uses an off-axis parabolic mirror, enabling high-precision collimation over a large aperture range. A controllable divergence angle beam refers to a beam with a specific divergence angle after exiting the collimation module. This divergence angle can be adjusted according to testing requirements to match the field-of-view coverage requirements of receiving antennas of different apertures.

[0033] A visible light-assisted alignment module refers to a functional unit that uses a laser beam visible to the human eye to assist in coarse alignment of the optical axis. For example, this module uses a 532-nanometer green laser, leveraging the high visibility of green light to help operators quickly determine the beam direction and approximate position. A visible light laser refers to a light source device that emits laser light in the visible wavelength range. The beam emitted is combined with the main optical path by an optical system and then emitted coaxially to indicate the spatial position of invisible communication light.

[0034] The control module can refer to the core unit responsible for coordinating the working status, parameter settings and process management of each submodule. For example, this module uses an industrial tablet or laptop computer equipped with dedicated monitoring software, and exchanges data and issues commands to each module through a communication interface to achieve unified scheduling of the system.

[0035] The present application will be further described below through a detailed embodiment: In one embodiment of the portable laser communication far-field calibration source device of this application, the device needs to perform calibration testing on a large-aperture ground station receiving antenna at a test distance of 2000 meters and a receiving antenna aperture of 1000 millimeters.

[0036] The device includes a light source module, a double wedge prism divergence angle adjustment module, a deformable mirror turbulence simulation module, an aspherical mirror collimation module, a visible light-assisted alignment module, and a control module. All modules are integrated and packaged in a precision aluminum chassis, with overall dimensions not exceeding 400 mm × 300 mm × 200 mm and a total weight not exceeding 15 kg. It is supported and fixed at the test site by a tripod.

[0037] The light source module uses a wavelength-tunable semiconductor laser as the light source, outputting near-infrared laser light with a wavelength of 1550 nm and a power setting of 10 milliwatts, with power stability better than ±0.5%. After transmission through a single-mode fiber, the laser beam exits from the fiber optic mount and enters the subsequent optical channel. The exit end face of the fiber optic mount is located near the focal plane of the aspherical mirror, giving the outgoing beam appropriate initial divergence characteristics.

[0038] The dual-wedge prism divergence angle adjustment module is positioned after the light source module along the optical path. The first wedge prism is fixedly mounted on the base plate, with its flat side facing the light source module and its wedge-shaped side facing the second wedge prism. The second wedge prism is mounted on a high-precision displacement slide, driven by a stepper motor and ball screw, with a stroke of 30 mm and a positioning accuracy better than 1 micrometer. Both wedge prisms are made of fused silica material, with a wedge angle designed to be 3 milliradians, and both sides are coated with anti-reflection coatings corresponding to the working wavelength. The control module communicates with the slide driver via an RS232 interface, sending target displacement commands. The slide driver then drives the second wedge prism to move along the inclined plane. As the second wedge prism moves, the effective optical thickness of the overlapping area of ​​the two prism inclined planes changes, altering the wavefront curvature of the emitted beam, thereby achieving continuous adjustment of the divergence angle. After calibration, the module's divergence angle adjustment range is 0.15 milliradians to 5 milliradians, fully covering the field of view requirements of a 1000 mm aperture receiving antenna at a test distance of 2000 meters.

[0039] The deformable mirror turbulence simulation module is positioned along the optical path after the double-wedge prism divergence angle adjustment module. The deformable mirror is a continuous-surface deformable mirror with a 61-element piezoelectric actuator array, a mirror aperture of 25 mm, and coated with a broadband high-reflectivity dielectric film. The high-voltage amplifier is a 61-channel independently controllable high-voltage amplifier with an output voltage range of 0 to 300 volts and a resolution of 12 bits. The control module generates a target phase screen based on user-defined turbulence parameters, solves for the driving voltage of each channel using a pre-calibrated influence matrix, and sends the voltage command to the high-voltage amplifier. The high-voltage amplifier drives each channel of the deformable mirror to produce a corresponding mirror displacement, forming a surface distribution consistent with the target phase screen. After the beam is reflected by the deformable mirror, it carries the corresponding wavefront phase distortion, thus simulating the atmospheric turbulence effect.

[0040] The aspherical mirror collimation module is positioned after the deformable mirror turbulence simulation module along the optical path. This module uses an off-axis parabolic mirror with a focal length of 500 mm, made of silicon carbide, and has a reflectivity of no less than 98% in the operating wavelength range. After the beam has undergone divergence angle adjustment by the double wedge prisms and turbulence simulation by the deformable mirror, it is incident on the off-axis parabolic mirror and collimated into a parallel or approximately parallel beam with the target divergence angle. The diameter of the emitted beam is adapted to the aperture coverage requirements of the receiving antenna.

[0041] The visible light-assisted alignment module is mounted on the side of the device. This module uses a 532nm semiconductor-pumped solid-state laser with an output power of 5 milliwatts, a beam quality factor of less than 1.3, and a divergence angle of less than 1 milliradian. The visible light laser undergoes coaxial calibration before leaving the factory to ensure that its emitted green light is coaxial with the main optical path of the communication band laser. During the on-site alignment phase, the operator turns on the visible light laser, emitting a green reference beam. Through visual observation or monitoring with a standard CCD camera, the overall orientation of the device is adjusted so that the green light spot is approximately located in the center area of ​​the receiving antenna, completing the coarse alignment.

[0042] The control module uses an industrial panel PC as the host computer, running monitoring software developed based on Qt. The control module communicates with each submodule via an Ethernet interface, enabling unified and coordinated functions such as divergence angle setting, turbulence parameter configuration, and visible light switch control. The monitoring software provides a human-machine interface, allowing operators to input parameters such as the target divergence angle and turbulence intensity. The software automatically calculates the control quantities for each actuator and issues commands.

[0043] The system operates as follows: The operator fixes the device to the test site using a tripod and levels it. The visible light laser is then activated for coarse alignment, ensuring the green light spot falls into the receiving antenna's field of view. After coarse alignment, the visible light is turned off, and the system switches to the communication band laser for fine alignment via optical power feedback from the receiver. Once aligned, the operator sets the target divergence angle and turbulence parameters on the control software interface. The system automatically drives the second wedge prism to the target position and loads a deformable mirror shape, emitting a simulated beam for calibration testing of the receiving system under test.

[0044] The beneficial effects of one of the embodiments in this specification include at least the following: by constructing a portable laser communication far-field calibration source device that integrates a light source module, a double wedge prism divergence angle adjustment module, a deformable mirror turbulence simulation module, an aspherical mirror collimation module, a visible light-assisted alignment module, and a control module, a single device can complete multi-dimensional calibration functions such as divergence angle adjustment, turbulence simulation, and assisted alignment. Its beneficial effects are that it significantly reduces the size and weight of the test equipment, avoids the accuracy loss caused by repeated assembly and adjustment and repositioning when using multiple independent devices, and solves the problem of assembly and adjustment difficulties caused by the invisibility of near-infrared light through the visible light-assisted alignment function, providing an efficient and convenient integrated solution for on-site calibration and field testing of satellite-to-ground laser communication ground stations.

[0045] In one possible implementation, the double wedge prism divergence angle adjustment module also includes a high-precision displacement slide and a slide driver. The second wedge prism is mounted on the high-precision displacement slide, which is driven by a piezoelectric ceramic or by a stepper motor in conjunction with a ball screw. The slide driver is connected to the control module to receive displacement commands and feedback the actual position.

[0046] Among them, a high-precision displacement slide can refer to a mechanical actuator used to support a second wedge prism and achieve precise translational motion. For example, this slide uses crossed roller guides as guiding elements, possessing high rigidity and low friction characteristics, and can achieve micron-level or even sub-micron-level motion resolution. Piezoelectric ceramic drive can refer to a driving method that utilizes the inverse piezoelectric effect of piezoelectric ceramics to convert electrical energy into minute mechanical displacements. For example, a stacked piezoelectric ceramic actuator can be used to generate nanometer-level step displacements by applying a control voltage, featuring fast response and high resolution. Stepper motor combined with ball screw drive can refer to a driving method that converts the rotational motion of a stepper motor into linear motion through a ball screw pair. For example, a two-phase hybrid stepper motor can be used to drive the ball screw to rotate, and the screw nut can drive the slide to move linearly along the guide rail, featuring large stroke and high holding torque. A slide table driver can refer to an electronic control unit that receives control commands and drives the movement of a displacement slide table. For example, the driver has a built-in microprocessor and power amplifier circuit, which can convert the displacement commands sent by the host computer into corresponding drive signals, and at the same time read the actual position of the slide table through a grating ruler or encoder and feed it back to the host computer.

[0047] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned portable laser communication far-field calibration source device, the dual-wedge prism divergence angle adjustment module further includes a high-precision displacement slide and a slide driver. The second wedge prism is fixedly mounted on the moving platform of the high-precision displacement slide using a precision clamp.

[0048] The high-precision displacement slide uses a cross roller guide as its guiding mechanism, with rolling contact between the slider and the guide rail, resulting in low friction and smooth movement. In this embodiment, the slide employs a stepper motor and ball screw drive scheme. The stepper motor is a two-phase hybrid stepper motor with a step angle of 1.8 degrees, which is further subdivided into 12,800 steps per revolution using microstepping technology. The ball screw has a lead of 2 mm, and the screw nut is fixedly connected to the slide's moving platform. When the stepper motor rotates, the ball screw drives the nut and the moving platform to move linearly along the guide rail. For each pulse signal received by the stepper motor, the theoretical displacement of the slide is approximately 0.156 micrometers, meeting the requirements for high-precision divergence angle adjustment. The total stroke of the slide is 30 mm, covering the displacement required for the full range of divergence angle adjustment.

[0049] The slide table driver employs a high-performance micro-stepping driver with a built-in current vector control algorithm. This algorithm automatically adjusts the current magnitude and phase of each phase to achieve smooth motion with low vibration and low noise. The slide table driver communicates with the control module via a USB interface, receiving displacement commands from the control module. These commands include target position information and motion speed parameters. Upon receiving the command, the slide table driver converts it into a pulse sequence and direction signal for the stepper motor, driving the motor to rotate to the target position. During motion, the slide table driver reads the feedback signal from the grating ruler displacement sensor mounted on the slide table in real time. The grating ruler has a resolution of 0.1 micrometers. The slide table driver feeds back the actual position data to the control module through the communication interface. The control module uses this data to determine whether the slide table has reached the target position and whether the motion is smooth. If the deviation between the actual position and the target position exceeds a preset tolerance, the control module issues a compensation command for correction.

[0050] In another implementation, the high-precision displacement slide stage employs a piezoelectric ceramic drive scheme. The piezoelectric ceramic actuator uses a stacked structure, generating a displacement output of 0 to 50 micrometers by applying a drive voltage of 0 to 150 volts. Combined with a flexible hinge amplification mechanism, the displacement stroke can be extended to the millimeter level. The piezoelectric ceramic actuator has the advantages of high resonant frequency and fast response speed, making it suitable for applications requiring rapid dynamic adjustment of the divergence angle. The slide stage actuator correspondingly uses a high-voltage operational amplifier circuit to amplify the low-voltage analog signal output from the control module into the drive voltage required by the piezoelectric ceramic. Simultaneously, closed-loop position control is achieved through a capacitive displacement sensor integrated into the slide stage, achieving a positioning accuracy at the nanometer level.

[0051] The beneficial effects of one of the embodiments in this specification include at least the following: by configuring a high-precision displacement slide and slide driver for the double wedge prism divergence angle adjustment module, precise control of the displacement of the second wedge prism inclined plane is achieved. The beneficial effect is that it ensures the repeatability and long-term stability of the divergence angle adjustment. At the same time, the position feedback function of the slide driver enables the control module to monitor the execution status in real time, improves the system's self-calibration capability for displacement deviation, and provides hardware guarantee for the accuracy and consistency of divergence angle calibration data.

[0052] In one possible implementation, the deformable mirror is a continuous surface piezoelectric deformable mirror containing a 61-unit piezoelectric actuator array arranged in a hexagonal pattern, with a mirror aperture of 25 mm and coated with a broadband high reflectivity dielectric film. The high voltage amplifier is a multi-channel high voltage amplifier, with each channel independently controllable, an output voltage range of 0 to 300 volts, and a resolution of not less than 12 bits.

[0053] Among them, a continuous-surface piezoelectric deformable mirror can refer to a reflective mirror with a continuous thin-plate structure on its surface, in which multiple piezoelectric actuators drive the mirror from behind to produce local deformation. For example, the mirror surface of this deformable mirror is a thin lens, and the actuators are bonded to the back of the mirror in a certain arrangement. When a voltage is applied to each actuator, the mirror produces a continuous deformable curved surface. A hexagonal 61-unit piezoelectric actuator array can refer to a layout in which the actuators are arranged in a honeycomb hexagonal grid on the back of the mirror. This arrangement can achieve uniform coverage of mirror deformation and high spatial frequency response. Mirror aperture can refer to the diameter of the effective reflection area of ​​the deformable mirror. A broadband high-reflectivity dielectric film can refer to a multilayer dielectric reflective film system deposited on the mirror surface, which can achieve high reflectivity simultaneously over a wide wavelength range, for example, a reflectivity of not less than 99.5% in the 850 nm to 1550 nm wavelength range. A multi-channel high-voltage amplifier can refer to an electronic device with multiple independent amplification channels, each channel corresponding to one actuator driving the deformable mirror, and the channels are independent of each other and do not interfere with each other. A resolution of at least 12 bits can refer to the digital control resolution of the output voltage of a high-voltage amplifier. For example, a 12-bit resolution corresponds to 4096 voltage levels, providing a voltage adjustment step of approximately 0.073 volts in the range of 0 to 300 volts.

[0054] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned portable laser communication far-field calibration source device, the deformable mirror is a continuous-surface piezoelectric deformable mirror. The mirror surface is an ultra-thin single-crystal silicon reflective mirror, only 0.5 mm thick, possessing excellent surface replication capability and optical quality. On the back of the mirror surface, 61 piezoelectric ceramic actuators are arranged in a hexagonal honeycomb pattern, forming a multi-layered ring array radiating outwards from the center. One actuator is arranged in the central region, six in the first ring, twelve in the second, eighteen in the third, and twenty-four in the fourth, totaling 61 actuators. This hexagonal arrangement ensures uniform coverage of the actuators, enabling the deformable mirror to accurately fit wavefront distortions at various spatial frequencies. The effective reflection area of ​​the mirror has an aperture of 25 mm, adapted to the spot size of the incident beam, ensuring that the entire beam falls within the effective area of ​​the deformable mirror. The mirror surface is coated with a broadband high-reflectivity dielectric film, which consists of alternating stacked high-refractive-index layers and low-refractive-index layers. After optimization design, the reflectivity is no less than 99.5% in the 850 nm to 1550 nm wavelength range, meeting the requirements for simultaneous reflection of laser and visible light assisted alignment beams in the communication band.

[0055] The high-voltage amplifier is a 61-channel independently controllable multi-channel high-voltage amplifier. Each channel contains an independent high-voltage operational amplifier circuit and a power output stage, capable of linearly amplifying the 0-5V low-voltage control signal output from the control module into a 0-300V high-voltage drive signal. Electrical isolation between channels is achieved using opto-isolation technology to avoid crosstalk and interference. Each channel has a 12-bit output voltage resolution, meaning each channel can divide the 0-300V range into 4096 programmable voltage levels, with a minimum voltage adjustment step of approximately 0.073V, sufficient to achieve micron-level or even sub-micron-level mirror deformation control accuracy. The high-voltage amplifier connects to the control module via a parallel interface, receiving the digital voltage setpoint signal from each channel, converting it to analog-to-digital conversion, and amplifying it before outputting it to the corresponding deformable mirror driver. All channels can be independently set with voltage values, enabling independent control of the 61 drivers, thereby synthesizing arbitrary target surface shapes.

[0056] During system operation, the control module calculates the target phase screen based on user-defined turbulence parameters and then solves for the driving voltage value of each channel using a pre-calibrated influence matrix. The driving voltage value is sent to the high-voltage amplifier in digital form via a parallel bus. Each channel of the high-voltage amplifier simultaneously performs digital-to-analog conversion and voltage amplification, synchronously driving the displacement of each actuator of the deformable mirror. The superposition of the displacements of each actuator forms a continuous surface shape change, applying corresponding wavefront phase modulation to the incident beam.

[0057] The beneficial effects of one of the embodiments in this specification include at least the following: by employing a continuous surface piezoelectric deformable mirror and a 61-channel independently controllable high-voltage amplifier, high spatial and temporal resolution phase modulation of the incident beam wavefront is achieved. Its beneficial effect is that it can accurately fit the wavefront distortion of various spatial frequency components predicted by Kolmogorov's turbulence theory. At the same time, the setting of a broadband high-reflectivity dielectric film enables the deformable mirror to have excellent optical performance in both the communication band and the visible light band, providing a hardware foundation for the realism of turbulence simulation and multi-wavelength compatible operation.

[0058] In one possible implementation, the visible light laser of the visible light-assisted alignment module is a 532 nm semiconductor-pumped solid-state laser. The visible light laser is fixed to the side of the device and is coaxially calibrated before leaving the factory to ensure that the visible light and the emitted beam of the light source module are coaxial.

[0059] Among them, the 532nm semiconductor-pumped solid-state laser refers to a laser that uses a semiconductor laser as a pump source to excite a solid-state gain medium to generate 532nm green light output. For example, this laser uses frequency doubling technology to convert 1064nm fundamental frequency light into 532nm green light, featuring good beam quality and high stability. "Fixed on the side of the device" means that the visible light laser is mounted on the side of the device chassis via a mechanical bracket, without occupying space in the main optical path. "Coaxial calibration" refers to the process of precisely aligning the output beam direction of the visible light laser with that of the main optical path communication laser before shipment. For example, by adjusting the precision adjustment screws on the laser mounting base, the elevation and azimuth angles of the visible light beam are changed until the visible light spot and the communication light spot coincide in the far field. "Coaxiality between the visible light and the output beam of the light source module" means that the two beams propagate along the same optical axis, and the centers of the two spots coincide at any position in the far field, allowing the visible light to accurately indicate the spatial position of the communication light.

[0060] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned portable laser communication far-field calibration source device, the visible light laser in the visible light-assisted alignment module is a 532 nm semiconductor-pumped solid-state laser. This laser internally includes a semiconductor pump source, a laser crystal, a frequency-doubling crystal, and an optical resonant cavity. The pump light emitted from the semiconductor pump source is focused and incident on the laser crystal. The laser crystal generates a 1064 nm fundamental frequency light through stimulated emission. After oscillation and enhancement within the resonant cavity, the fundamental frequency light undergoes nonlinear frequency transformation by the frequency-doubling crystal to generate a 532 nm frequency-doubled light output. The laser has an output power of 5 milliwatts, a beam quality factor of less than 1.3, a divergence angle of less than 1 milliradian, a beam pattern of fundamental transverse mode, and an ideal Gaussian beam distribution. 532 nm green light is one of the most sensitive spectral bands for the human eye and maintains good visibility even under clear daytime outdoor conditions.

[0061] The visible light laser is fixedly mounted on the right side of the device chassis using a precision mechanical bracket. This bracket is a six-dimensional precision adjustment frame, capable of fine-tuning multiple degrees of freedom, including pitch, yaw, and translation. During the pre-shipment assembly and adjustment phase, technicians align the device with a distant target and simultaneously activate the visible light laser and the light source module. An infrared observation card and a visible light receiving screen are placed at the target location to observe the positions of the communication light spot and the visible light spot, respectively. By adjusting the fine-tuning screws on the six-dimensional precision adjustment frame, technicians gradually change the direction of the visible light laser, causing the visible light spot to gradually move closer to the communication light spot. When the two spots completely overlap at the target, the locking screws on the adjustment frame are tightened to fix the position of the visible light laser. To further improve coaxial accuracy, technicians repeatedly check the overlap of the two spots at multiple different distances (e.g., 10 meters, 50 meters, 200 meters), making fine adjustments as necessary until the two spots overlap at all distances. After coaxial calibration, the angle between the output beam direction of the visible light laser and the output beam direction of the main optical path communication laser is less than 5 microradians, and the deviation of the spot center between the two can be ignored within the entire working distance.

[0062] During field use, after the operator turns on the visible light laser, the green beam emitted from the device represents the propagation direction of the communication light. By visually observing the position of the green light spot at the receiving end, the operator can quickly determine whether the communication light is aligned with the receiving antenna. When the green light spot falls within the field of view of the receiving antenna, since the two are coaxial, the communication light will also fall within the field of view of the receiving antenna, and the rough alignment is completed.

[0063] The beneficial effects of one of the embodiments in this specification include at least the following: by using a 532 nm semiconductor-pumped solid-state laser as a visible light-assisted alignment light source and coaxially calibrating it before leaving the factory, precise coaxial emission of visible indicator light and invisible communication light is achieved. Its beneficial effect is that it provides an intuitive alignment reference for on-site operators, greatly reduces the alignment difficulty caused by the invisibility of near-infrared light, and at the same time, the high brightness characteristics of 532 nm green light make it clearly visible under sunlight conditions, expanding the applicability of the device in outdoor strong light environments.

[0064] In one possible implementation, the aspherical mirror collimation module includes an off-axis parabolic mirror made of silicon carbide, which has a reflectivity of not less than 98% in the operating wavelength range.

[0065] Off-axis parabolic mirrors can refer to mirrors whose reflecting surface is part of a parabola, and whose axis of symmetry is separate from the incident light axis. For example, such mirrors utilize the geometric properties of a parabola to reflect a point light source at its focal point into a collimated parallel beam. The off-axis design avoids central obstruction, resulting in a diffraction-free outgoing beam and higher beam quality. Silicon carbide can refer to a ceramic material composed of silicon and carbon, such as reaction-bonded silicon carbide or chemical vapor-deposited silicon carbide. This material has high specific stiffness, low coefficient of thermal expansion, high thermal conductivity, and good machinability, making it a preferred material for large-aperture optical mirrors. A reflectivity of not less than 98% within the operating wavelength band means that, within the wavelength range of laser light in the communication band, the ratio of reflected power to incident power on the surface of the off-axis parabolic mirror is not less than 98%. This high reflectivity is achieved, for example, by depositing a metal film or dielectric film, ensuring minimal energy loss after the beam passes through the mirror.

[0066] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned portable laser communication far-field calibration source device, the aspherical mirror collimation module includes an off-axis parabolic mirror. This off-axis parabolic mirror has an effective focal length of 500 mm, an off-axis distance of 150 mm, and an effective aperture of 100 mm, which can meet the aperture requirements of the emitted beam of this device. The substrate material of the mirror is reaction-bonded silicon carbide. The preparation process of this material is as follows: silicon carbide powder and carbon powder are mixed and pressed into shape, and then sintered at high temperature to allow carbon and silicon to react and form a silicon carbide bond phase, ultimately obtaining a dense silicon carbide ceramic body. Reaction-bonded silicon carbide has excellent mechanical and thermal properties: its elastic modulus is as high as approximately 400 GPa, and its specific stiffness is about three times that of steel, which can significantly reduce the weight of the mirror body while maintaining high rigidity; its coefficient of thermal expansion is approximately 2.5 × 10⁻⁶ / °C. -6 It exhibits excellent thermal dimensional stability, with minimal changes in mirror surface shape due to variations in ambient temperature; its thermal conductivity is approximately 150 Kelvin per meter, which helps to homogenize the internal temperature of the mirror and reduce thermal deformation. After precision grinding and polishing, the silicon carbide mirror blank has a surface roughness better than 1 nanometer root mean square and a surface shape accuracy better than one-tenth of the wavelength.

[0067] The reflective surface of the off-axis parabolic mirror is coated with a protective silver film. The coating process is as follows: First, a nickel-chromium alloy layer is deposited on a silicon carbide substrate as a transition layer to enhance film adhesion; then, a silver film is deposited as the main reflective layer, with a reflectivity exceeding 98% in the near-infrared band; finally, a layer of silicon dioxide or silicon nitride is deposited on the surface of the silver film as a protective layer to prevent oxidation and scratches. The protective silver film has an average reflectivity of no less than 98% over the total internal reflection bandwidth (800 nm to 1600 nm), and a reflectivity of 98.5% at a wavelength of 1550 nm, ensuring the energy retention rate of laser light reflected in the communication band.

[0068] In the optical path, the off-axis parabolic mirror is installed by fixing it to the base plate of the device using a flexible support structure. The flexible support employs a three-point positioning method, effectively isolating external vibrations from interfering with the mirror's surface shape. The focal plane of the mirror coincides with the exit face of the fiber optic mount of the light source module, ensuring that the beam emitted from the fiber optic mount and modulated by the double wedge prism and deformable mirror lies precisely on the focal plane of the mirror. After reflection, the output is either parallel light or a beam with a controllable divergence angle. The off-axis design of the off-axis parabolic mirror separates the incident and exit optical paths, avoiding energy loss and diffraction effects caused by central obstruction in coaxial parabolic mirrors, resulting in a more uniform energy distribution of the exit beam.

[0069] The beneficial effects of one of the embodiments in this specification include at least the following: by using an off-axis parabolic mirror made of silicon carbide as a collimating element, a large-aperture, high-reflectivity, and high-thermal-stability beam collimation output is achieved. The beneficial effects are that the high specific stiffness of silicon carbide ensures the surface stability of the mirror under vibration and gravity, the low coefficient of thermal expansion ensures the consistency of optical performance over a wide temperature range, the reflectivity of more than 98% reduces the energy loss of the optical path, and the off-axis design eliminates central obstruction, improving the quality and uniformity of the emitted beam, providing key optical assurance for the high-precision calibration function of this device.

[0070] See Figure 2 , Figure 2 A flowchart of a portable laser communication far-field calibration source device according to an embodiment of this specification is shown, which specifically includes the following steps.

[0071] Step 201: Place the portable laser communication far-field calibration source device in front of the laser communication terminal under test, fix it with a tripod and level it; Step 202: Activate the visible light-assisted alignment module, emit a visible reference beam, and adjust the overall attitude of the portable laser communication far-field calibration source device so that the visible light spot is located in the center area of ​​the receiving antenna of the laser communication terminal under test, thus completing the coarse alignment; Step 203: Turn off the visible light-assisted alignment module, switch to the communication band laser emission of the light source module, turn on the optical power monitoring function of the laser communication terminal under test, and record the received optical power in real time; Step 204: Using the coarse alignment position as the center, perform a step scan on the portable laser communication far-field calibration source device or the laser communication terminal under test in the pitch and azimuth directions. Record the current received optical power for each step. Move the pointing position to the point where the received power is the maximum to complete the fine alignment. Step 205: Set the target divergence angle through the control module. The control module checks the target displacement of the second wedge prism based on the pre-stored calibration data and drives the second wedge prism to move to the target position so that the divergence angle of the emitted beam covers the receiving field of view of the receiving antenna. Step 206: Set the simulation scene parameters through the control module, generate a turbulent phase screen that conforms to Kolmogorov statistical theory, calculate the driving voltage sequence of the deformable mirror, apply the driving voltage sequence to the deformable mirror to make the deformable mirror produce a corresponding surface shape change, apply wavefront phase distortion to the beam to simulate atmospheric turbulence effect; Step 207: Turn on the scanning and capture mode of the laser communication terminal under test, turn on the output of the portable laser communication far-field calibration source device, record the time from the start of scanning to successful capture, repeat multiple times, and calculate the average capture time and capture success rate.

[0072] The calibration method refers to the complete operational process of using a calibration source device to perform performance testing and parameter calibration of the laser communication system under test. This process may include steps such as optical axis alignment, divergence angle setting, turbulence simulation, and capture performance testing. The laser communication terminal under test can refer to laser communication equipment requiring calibration testing, such as a satellite-to-ground laser communication ground station, a vehicle-mounted mobile laser communication terminal, or a solid-state laser communication terminal. Coarse alignment refers to the stage of roughly guiding the beam into the receiver's field of view using visible light indication. This stage has lower precision requirements, aiming to ensure the beam falls within the receiving antenna's field of view. Fine alignment refers to the stage of high-precision pointing adjustment based on coarse alignment, using receiver optical power feedback. This stage achieves optimal beam direction adjustment through power maximization search. Calibration data refers to the set of data characterizing the relationship between the displacement of the second wedge prism and the divergence angle of the emitted beam, obtained through precise measurements before leaving the factory or under laboratory conditions. Simulated scenario parameters refer to a set of parameters used to describe the atmospheric conditions of a specific satellite-to-ground laser communication link, such as satellite orbital altitude, zenith angle, ground refractive index structure constant, and equivalent wind speed. Scanning acquisition mode refers to the operating mode of the laser communication terminal under test, which scans the airspace according to a predetermined search trajectory to find the beacon light signal when it does not receive the beacon light. Acquisition time refers to the length of time from when the terminal under test begins its scan to when it successfully locks onto the beacon light signal.

[0073] The present application will be further described below through a detailed embodiment: In the embodiment of using the aforementioned portable laser communication far-field calibration source device to calibrate and test a satellite-to-ground laser communication ground station, the ground station under test is located on the roof of a building, and the receiving antenna has a diameter of 1000 mm. The operator fixes the device on a tripod in an open area 2000 meters in front of the ground station, and uses a level to adjust the tripod to ensure that the device is in a horizontal position, ensuring that the reference level of the emitted beam is horizontal.

[0074] The operator activates the visible light-assisted alignment module, and the 532nm green laser emits a green reference beam. The operator observes the position of the green laser spot near the ground station's receiving antenna through a telescope, and manually adjusts the pitch and azimuth knobs of the tripod head to gradually move the green laser spot to the center area of ​​the receiving antenna's reflector. During this process, the ground station operator observes whether the green laser spot falls into the field of view through an internal monitoring camera and coordinates the direction adjustment with the on-site operator via voice communication. When the green laser spot stably appears at the center of the receiving antenna without significant drift, coarse alignment is complete. At this point, the angle between the beam direction and the receiving antenna's field of view is less than 0.1 milliradians, and the beam has fallen into the receiving antenna's acquisition field of view.

[0075] The operator shuts down the visible light laser and switches to the 1550nm communication laser output from the light source module via the control module. The ground station operator activates the built-in optical power monitoring function of the receiver, recording the received optical power value in real time and transmitting it back to the control module display interface on the device via data link. The control module's monitoring software automatically generates a two-dimensional scanning trajectory in the pitch and azimuth directions, using the coarse alignment position as the scanning center. The scanning trajectory is spiral-shaped, starting with a radius of 50 microradians and gradually expanding to 500 microradians, with a step interval of 20 microradians. The control module controls the device to move along the predetermined trajectory in the pitch and azimuth directions via gimbal drive commands, pausing for 0.5 seconds after reaching each scanning point to record the received optical power value transmitted back from the ground station. After scanning, the control module finds the position with the highest received optical power among all scanning points and drives the gimbal back to that position. Subsequently, the control module performs a second round of fine scanning centered on this position, with a scanning range of 100 microradians and a step interval reduced to 5 microradians, repeating the power recording and optimal position search process. After two rounds of scanning, the optical power value at the final aligned position reached the global maximum value, and fine alignment was completed with a pointing accuracy better than 10 microradians.

[0076] After alignment, the operator inputs a target divergence angle of 500 microradians through the monitoring software of the control module. The control module performs a reverse lookup based on a pre-stored displacement-divergence angle calibration lookup table, calculating the target displacement of the second wedge prism corresponding to a divergence angle of 500 microradians as 15.2 millimeters. The control module sends the target displacement command to the slide driver via the communication interface. The slide driver drives the stepper motor, moving the second wedge prism along the inclined plane. During the slide movement, the slide driver reads the displacement feedback signal from the grating ruler in real time. When the actual position approaches the target position, it switches to a low-speed crawling mode, slowly approaching the target position at a speed of 0.5 millimeters per minute, ultimately achieving a positioning accuracy better than 1 micrometer. After reaching the target position, the control module reads the feedback confirmation, and the divergence angle adjustment is complete.

[0077] Operators set the simulation scenario parameters through the control module's monitoring software: satellite orbital altitude of 500 km, zenith angle of 30 degrees, ground refractive index structure constant on the order of -13 per cubic meter, and equivalent wind speed of 10 m / s. Based on these parameters, the control module automatically calculated the equivalent Fried parameter to be approximately 12 cm and the equivalent Greenwood frequency to be approximately 20 Hz. The control module then executed a turbulence phase screen generation algorithm, generating a sequence of 500 phase screen frames conforming to Kolmogorov statistical theory, with each frame having a spatial sampling of 256×256. According to the pre-calibrated deformable mirror influence matrix, the control module used regularized least squares to map each phase screen frame to a 61-channel driving voltage vector, generating 500 sets of driving voltage sequences. After calculation, the control module sent the first set of driving voltages to a high-voltage amplifier, which drove the deformable mirror to produce corresponding surface shape changes, applying wavefront phase distortion to the beam. Subsequently, the control module continuously loaded the driving voltages corresponding to subsequent phase screens at a refresh rate of 500 frames per second, achieving dynamic turbulence simulation.

[0078] After activating the turbulence simulation, the control module shuts down the laser output of the device, ensuring the ground station receiver receives no light signal. The ground station operator switches the terminal to scan-and-acquire mode, causing the receiving antenna to scan the airspace along a predetermined search trajectory. Subsequently, the control module reactivates the laser output and starts a timer. Upon detecting the incident beacon light during the scan, the ground station terminal automatically stops scanning and enters tracking mode, simultaneously sending a successful acquisition signal to the control module. Upon receiving the successful acquisition signal, the control module stops the timer and records the acquisition time. This process of activating output, waiting for acquisition, and recording time is repeated 50 times, half with the turbulence simulation enabled and the other half with it disabled for comparison. After 50 tests, the control module automatically calculates the average acquisition time and success rate under both conditions and generates a test report.

[0079] The beneficial effects of one of the embodiments in this specification include at least the following: by providing a complete calibration method and process, coarse alignment, fine alignment, divergence angle adjustment, turbulence simulation and capture performance testing are sequentially connected, realizing the whole process calibration of laser communication terminals from alignment to performance evaluation. Its beneficial effects are that the method does not require additional wavefront sensors or position detectors, and can complete high-precision alignment by utilizing the power monitoring function of the terminal under test itself, which greatly simplifies the hardware requirements and operation process of the calibration system. At the same time, through the statistical evaluation method of repeated testing, the impact of turbulence on capture performance can be objectively quantified, providing a reliable technical means for evaluating the anti-turbulence capability of laser communication systems.

[0080] In one possible implementation, during the fine alignment step, the scanning step size is gradually reduced from 50 microradians to 5 microradians until the received power reaches a stable maximum value, and the received power at the final aligned position is recorded as the calibration reference.

[0081] The scan step size refers to the angular interval between two adjacent scan positions during fine alignment scanning, such as the angular distance adjusted each time in the pitch or azimuth direction. Gradually decreasing the scan step size means that in multiple rounds of fine alignment scanning, the step size of each subsequent scan is smaller than that of the previous scan. For example, the first round uses a large step size of 50 microradians for rapid coarse searching, the second round uses a medium step size of 20 microradians for fine searching, and the third round uses a small step size of 5 microradians for fine adjustment. The stable maximum value refers to the state where the received optical power reaches its peak value as the scan position changes, and the deviation between adjacent measurements is less than a preset tolerance. For example, after repeated measurements near the optimal position, the power is considered to have reached its stable maximum value when the deviation between power readings is less than 0.5 dB. The calibration benchmark refers to the received power value used as a reference standard for subsequent performance evaluation. For example, the highest received power measured after fine alignment is used as the benchmark value for link loss calculation and communication quality evaluation.

[0082] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned calibration method, the fine alignment step employs a scanning strategy with progressively smaller step sizes to achieve high-precision alignment. After coarse alignment is completed, the control module initiates the first round of fine scanning. The starting position of the first round of scanning is the coarse alignment position, and the scanning range is a square area with a side length of 200 microradians centered at this position. The control module generates two-dimensional grid scanning trajectories in the pitch and azimuth directions, with a scanning step size set to 50 microradians, meaning that the interval between each scanning point in both the pitch and azimuth directions is 50 microradians. The entire scanning area contains 25 scanning points in a 5×5 pattern. The control module drives the pan-tilt unit to point sequentially at each scanning point, pausing at each point for 1 second, and reads and records the optical power meter readings from the ground station receiver via the data link. After completing the measurement of all 25 points, the control module compares the power values ​​of each point and identifies the point with the highest power as the optimal position for this round.

[0083] The control module moves the pan-tilt unit to the optimal position in the first round and initiates the second round of fine scanning. The scanning area in the second round is narrowed to a square region with a side length of 100 microradians centered on that position, and the scanning step size is reduced to 20 microradians. The scanning point array consists of 25 points in a 5×5 pattern. Similarly, the control module sequentially measures the received optical power at each point, records and compares the data to find the optimal position in the second round. The accuracy of the optimal position in this round of scanning is further improved compared to the first round, and the reduced step size results in a finer search resolution.

[0084] The control module moves the pan-tilt unit to the optimal position for the second round, initiating the third round of fine scanning. The third round of scanning further narrows the area to a square region with sides of 40 microradians, and the scanning step size is reduced to 5 microradians. The scanning dot matrix remains 5×5, totaling 25 points, offering a smaller coverage area and higher resolution. The optimal position is determined after this round of measurement.

[0085] After three rounds of progressively smaller scans, the control module determined the final optimal pointing position. To verify whether the received power had reached a stable maximum value, the control module drove the pan-tilt unit to stay at this optimal position and continuously measured the received optical power 10 times, with each measurement interval of 0.5 seconds. If the peak-to-peak deviation of the 10 measurements was less than 0.3 dB, the power was considered to have reached a stable maximum value. If the deviation exceeded the tolerance, the control module performed an additional round of ultra-fine scanning with a step size of 2 microradians centered on that position for correction. After confirming stability, the control module recorded the received optical power value at that position as the baseline power value for this calibration. This baseline value is used for subsequent link budget analysis and communication performance evaluation.

[0086] The beneficial effects of one of the embodiments in this specification include at least the following: by adopting a fine alignment strategy that gradually reduces the scanning step size, the alignment resolution is gradually improved while ensuring the search coverage. The beneficial effects are that it takes into account both scanning efficiency and final alignment accuracy, avoids the problem of excessive scanning time caused by using small step sizes throughout the process, and also avoids the risk of missing the optimal position caused by using large step sizes throughout the process. At the same time, the reliability and repeatability of the reference power value are ensured by the confirmation mechanism of the stable maximum value, providing an accurate power reference benchmark for subsequent calibration tests.

[0087] In one possible implementation, the generation of the turbulent phase screen employs a power spectrum inversion method combined with subharmonic compensation. Specifically, this includes: inputting simulated scenario parameters, including satellite orbital altitude, zenith angle, ground refractive index structure constant, and equivalent wind speed; calculating the equivalent Fried parameters and equivalent Greenwood frequency; performing frequency domain filtering using a modified von Karman power spectrum and obtaining the initial phase screen through inverse Fourier transform; performing subharmonic sampling in the low-frequency region to generate a compensated phase screen; superimposing the compensated phase screen onto the initial phase screen to obtain the target phase screen; and verifying the consistency between the phase structure function of the target phase screen and the theoretical value. If the deviation is less than 10%, the target phase screen is confirmed to be effective.

[0088] Among these, the power spectrum inversion method refers to a method based on the statistical power spectral density function of atmospheric turbulence, generating a random phase distribution conforming to this power spectrum in the frequency domain, and then transforming it to the spatial domain via inverse Fourier transform to obtain the turbulence phase screen. Subharmonic compensation refers to a method based on the power spectrum inversion method that compensates for the large-scale phase information loss caused by insufficient sampling in the low-frequency part of the Fourier transform by adding additional sampling points in the low-frequency region. Simulated scene parameters refer to a set of input parameters used to describe the environment and orbital conditions of a specific satellite-to-ground laser communication link. Equivalent Fried parameters refer to the parameter that equates the turbulence intensity varying with altitude across the entire satellite-to-ground link to the coherence length on a single uniform path, used to characterize the comprehensive influence of turbulence on light wave propagation. Equivalent Greenwood frequency refers to the parameter that equates the dynamic turbulence effect of the entire link to a single frequency parameter, used to characterize the time-varying rate of turbulence. The modified von Karman power spectrum can refer to a mathematical model describing the spatial statistical characteristics of refractive index fluctuations in atmospheric turbulence. This model introduces external and internal scale parameters, resolving the singularity problem of the classical Kolmogorov spectrum in the low-frequency and high-frequency regions. The phase structure function can refer to a function describing the statistical characteristics of the phase difference between two points on a phase screen, for example, defined as the ensemble average of the squares of the phase difference between the two points, used to characterize the spatial correlation characteristics of turbulence.

[0089] The present application will be further described below through a detailed embodiment: In one implementation of the aforementioned calibration method, the turbulent phase screen is generated using a power spectrum inversion method combined with subharmonic compensation. The implementation process is as follows: Users input simulation scenario parameters through the monitoring software interface of the control module. For simulating a downlink scenario from a low-Earth orbit satellite to a ground station, the input parameters include: satellite orbital altitude of 500 km, zenith angle of 45 degrees, ground refractive index structure constant on the order of -14 m / s, and equivalent wind speed of 8 m / s. The control module automatically calculates the equivalent Fried parameters and equivalent Greenwood frequency based on the input parameters. Specifically, the control module divides the atmosphere into several layers along the altitude direction, assigns a refractive index structure constant related to altitude to each layer, calculates the slant path length of each layer based on the zenith angle, and then performs a weighted integral of the turbulence intensity of each layer according to the theoretical formula to obtain the equivalent Fried parameters for the entire link. Simultaneously, the control module calculates the equivalent Greenwood frequency based on the equivalent wind speed and equivalent Fried parameters.

[0090] The control module then enters the phase screen generation process. First, it generates two independent standard normally distributed random number matrices, each 256×256, representing the real and imaginary parts of the complex random field in the frequency domain, respectively. The control module calculates the modified von Karman power spectrum, which is constrained to a finite value in the low-frequency region to avoid zero-frequency divergence and decays exponentially in the high-frequency region to simulate internal scaling effects. The control module combines the two random number matrices into a complex random field, performs frequency domain filtering on this complex random field using the square root of the modified von Karman power spectrum, and then performs a two-dimensional inverse Fourier transform to obtain the initial phase screen in the spatial domain. This initial phase screen contains phase information from high to mid-frequency, but the large-scale structure at low frequencies is not accurately represented due to insufficient discrete sampling density of the Fourier transform in the low-frequency region.

[0091] To compensate for the lack of low-frequency information, the control module executes a subharmonic compensation process. The control module sets the number of subharmonic layers to four, covering the frequency bands that gradually extend towards lower frequencies, from the first to the fourth layer. For each harmonic layer, the control module samples the corresponding low-frequency region according to the power spectrum, with three sampling points in each direction, for a total of nine low-frequency sampling points. After performing phase randomization processing on the sampled data for each layer, the control module performs an inverse Fourier transform to generate a compensated phase screen for that layer. The four compensated phase screens are then superimposed point-by-point with the initial phase screen to obtain the final target phase screen. In this target phase screen, large-scale turbulent vortex structures are significantly enhanced, and the spatial distribution more closely matches the statistical characteristics of actual atmospheric turbulence.

[0092] After generating the target phase screen, the control module verifies its effectiveness. The control module randomly selects a large number of point pairs within the target phase screen, calculates the squared phase difference of each point pair, and performs ensemble averaging to obtain the actual phase structure function curve. The control module compares this curve with the theoretical structure function, which is calculated from the equivalent Fried parameters using theoretical formulas. The control module calculates the relative deviation between the two at various spatial scales. If the maximum deviation is less than 10%, the generated phase screen is considered effective and can be used for subsequent deformable mirror actuation. If the deviation exceeds 10%, the control module adjusts the number of subharmonic layers or the sampling density, and regenerates the phase screen until the accuracy requirements are met.

[0093] The beneficial effects of one of the embodiments in this specification include at least the following: by using the power spectrum inversion method in conjunction with subharmonic compensation to generate a turbulent phase screen, the accurate reproduction of the statistical characteristics of Kolmogorov turbulence is achieved. The beneficial effect is that the subharmonic compensation effectively makes up for the lack of low-frequency information in the pure Fourier method, so that the generated phase screen conforms to the theoretical turbulence statistical law in the entire spatial frequency range from large scale to small scale. At the same time, the effectiveness of the phase screen is ensured by the phase structure function verification mechanism, providing high-fidelity target wavefront data for subsequent deformable mirror driving, and ensuring the quantitative accuracy and physical authenticity of turbulence simulation.

[0094] In one possible implementation, solving the driving voltage sequence includes: obtaining a pre-calibrated deformable mirror influence matrix, which is obtained by sequentially applying a unit voltage to each actuator and measuring the corresponding mirror deformation; using regularized least squares method to solve the driving voltage vector based on the target phase screen and the influence matrix, and improving the numerical stability of the driving voltage vector through singular value decomposition; and applying an open-loop surface change to the deformable mirror according to the solved driving voltage vector.

[0095] The deformable mirror influence matrix can refer to a matrix describing the linear relationship between the unit voltage of each actuator and the deformation at each position of the mirror surface. For example, each column of this matrix corresponds to the deformation distribution at all sampling points on the mirror surface after a unit voltage is applied to an actuator, the number of rows corresponds to the number of mirror deformation measurement points, and the number of columns corresponds to the number of actuators. Pre-calibration refers to the process of pre-measuring and recording the response characteristics of the deformable mirror using external measuring equipment before leaving the factory or during system maintenance. Unit voltage can refer to the standardized voltage value applied for calibrating the influence matrix, such as applying 1 volt to a single actuator. Regularized least squares can refer to a parameter estimation method that adds a regularization term to the least squares solution process to suppress high-frequency noise and overfitting in the solution vector. The actuator voltage vector can refer to a multidimensional vector containing the required voltage values ​​for all actuators, where the dimension of the vector equals the number of actuators, and each element corresponds to the voltage setpoint of one actuator. Singular value decomposition (SVD) can refer to a matrix decomposition method that decomposes a matrix into singular values ​​and singular vectors, effectively identifying and suppressing numerical instability caused by small singular values ​​when solving ill-conditioned linear equations. Open-loop application can refer to a voltage application method that does not rely on real-time wavefront sensor feedback, that is, the deformable mirror is directly driven according to the pre-calculated driving voltage value, and no real-time measurement and correction are performed during the application process.

[0096] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned calibration method, the driving voltage sequence is solved based on a pre-calibrated deformable mirror influence matrix.

[0097] The pre-calibration of the influence matrix is ​​completed during the calibration phase before the device leaves the factory. Calibration personnel mount the deformable mirror on an optical platform and place a high-precision interferometer in front of it, with the interferometer's test optical path covering the entire mirror surface area. The calibration process is as follows: First, in an initial state without any applied voltage, the interferometer measures the initial surface shape of the deformable mirror and records it as a reference. Then, the calibration personnel send instructions to the high-voltage amplifier via control software, sequentially applying a 1-volt driving voltage to each of the 61 actuators, while keeping the voltage of the other actuators at 0 volts. After applying voltage to each actuator, the interferometer measures the current mirror deformation distribution, subtracting the initial reference surface shape from the current surface shape to obtain the deformation response caused by a unit voltage of that actuator. This response is a column vector containing the deformation of a large number of measurement points. After performing the above operation sequentially on all 61 actuators, the calibration personnel combine the 61 column vectors in the order of the actuators into a complete matrix, which is the influence matrix of the deformable mirror. Each column of this matrix corresponds to one actuator, and the number of rows corresponds to the number of measurement points of the interferometer; the matrix size is tens of thousands of rows by 61 columns. After calibration, the influence matrix will be stored in the firmware of the control module for later use.

[0098] During actual calibration, after generating the target phase screen, the control module flattens the pixel values ​​of the target phase screen from a two-dimensional matrix into a one-dimensional column vector, with its dimension matching the number of rows in the influence matrix. The process of the control module solving for the driving voltage vector involves finding a 61-dimensional voltage vector such that the product of the influence matrix and this voltage vector approximates the target phase screen vector as closely as possible. Since the influence matrix is ​​typically ill-conditioned, directly solving for least squares can lead to severe voltage oscillations. Therefore, the control module employs regularized least squares. Specifically, the control module adds a regularization term to the objective function, which is the square of the L2 norm of the driving voltage vector multiplied by a regularization parameter set to 0.1%. This regularization term suppresses the amplitude divergence of the voltage vector, ensuring a smooth and feasible solution.

[0099] To efficiently and stably solve the aforementioned regularized least squares problem, the control module performs singular value decomposition on the influence matrix, decomposing it into the product of a left singular vector matrix, a singular value diagonal matrix, and a right singular vector matrix. The diagonal elements of the singular value diagonal matrix are singular values ​​arranged in descending order. The control module directly sets the smallest singular values ​​less than one percent of the largest singular value to zero to prevent these tiny singular values ​​from being amplified during the inversion process and causing numerical overflow. After singular value truncation, the control module calculates the generalized inverse matrix of the influence matrix, and multiplies this generalized inverse matrix by the target phase screen vector to obtain the driving voltage vector. This solution process can be completed within milliseconds, exhibiting extremely high numerical stability and computational efficiency.

[0100] The control module sends the solved 61-dimensional driving voltage vector to the high-voltage amplifier via a parallel bus. Each channel of the high-voltage amplifier simultaneously performs digital-to-analog conversion and power amplification, applying the corresponding driving voltage to each of the 61 actuators of the deformable mirror. Each actuator of the deformable mirror generates a corresponding displacement under the voltage. The superposition of all displacements forms a continuous mirror surface profile, which constitutes the optical representation of the target phase screen. Throughout the turbulence simulation, the control module solves for the driving voltage vector frame-by-frame according to a preset refresh rate and applies it in an open-loop manner, without relying on any real-time wavefront sensors for feedback correction.

[0101] The beneficial effects of one of the embodiments in this specification include at least the following: by solving the deformable mirror driving voltage using regularized least squares method and singular value decomposition based on a pre-calibrated influence matrix, an accurate mapping from the target phase screen to the driver voltage is achieved. The beneficial effects are that the pre-calibrated influence matrix accurately reflects the true response characteristics of the deformable mirror, the regularization process effectively suppresses voltage oscillations and overfitting during the solution process, the singular value decomposition ensures the numerical stability and computational efficiency of the solution, and the open-loop control method avoids the complex wavefront sensing hardware required by the closed-loop system, simplifies the system structure, reduces costs, and at the same time ensures the real-time performance and accuracy of turbulence simulation.

[0102] In one possible implementation, calibration data is obtained in advance through the following steps: a portable laser communication far-field calibration source device is fixed on a precision adjustment platform, the emitted beam is incident along the optical axis of a collimator, and a beam quality analyzer is installed at the focal plane of the collimator; the second wedge prism is moved to its initial position, the focal plane spot diameter is measured, and the current divergence angle is calculated; the second wedge prism is gradually moved from its initial position to its maximum stroke, and the actual divergence angle is repeatedly measured at each calibration point with a fixed step size, and the displacement and corresponding actual divergence angle of each calibration point are recorded; polynomial fitting is performed on the obtained discrete calibration data to establish an analytical relationship between the displacement and the divergence angle, and the fitted polynomial coefficients or the complete displacement-divergence angle lookup table are written into the firmware of the control module.

[0103] The calibration data can refer to all data obtained through experimental measurements that characterize the relationship between the displacement of the second wedge prism and the divergence angle of the emitted beam, including, for example, the displacement values ​​of each calibration point and the corresponding divergence angle measurements. The precision adjustment platform can refer to a mechanical platform capable of precise multi-degree-of-freedom positioning of the device, such as a five- or six-dimensional adjustment frame with pitch, yaw, height, and translation adjustment functions. The collimator can refer to an optical instrument capable of generating a standard collimated beam or precisely measuring the divergence angle of the incident beam, such as an off-axis reflective collimator with a long focal length and large aperture. The beam quality analyzer can refer to an optical measuring instrument used to measure the spatial distribution parameters of the beam, such as a beam profiler based on a CCD or CMOS camera, capable of accurately measuring parameters such as the diameter, ellipticity, and centroid position of the beam spot. The initial position can refer to the initial reference position of the second wedge prism, such as the starting point or midpoint of the travel, corresponding to the minimum divergence angle state. The fixed step size can refer to the equal displacement increment of the second wedge prism between adjacent calibration points, such as moving 2 millimeters each time. Polynomial fitting refers to a data processing method that uses a polynomial function to approximate discrete data points to obtain a continuous analytical relationship, such as using the least squares method to determine the coefficients of the polynomial. A lookup table refers to a data structure that stores the correspondence between displacement and divergence angle in tabular form, facilitating quick table lookup and interpolation in practical applications.

[0104] The present application will be further described below through a detailed embodiment: In one embodiment of the aforementioned calibration method, the calibration data is obtained through the following pre-calibration process: Calibration was conducted in a temperature-controlled environment within an optical laboratory, with the ambient temperature maintained within ±0.5 degrees Celsius of 22 degrees Celsius to minimize the impact of temperature variations on the refractive index and mechanical dimensions of the optical components. The calibration personnel fixed the device onto a precision six-dimensional adjustment platform, which offers precise adjustment capabilities in six degrees of freedom: pitch, yaw, roll, vertical movement, forward / backward translation, and left / right translation. The adjustment resolution for each degree of freedom is better than 1 microradian or 1 micrometer. After fixing the device, the calibration personnel adjusted the six-dimensional platform to ensure that the emitted beam was incident along the optical axis of the collimator. The collimator is an off-axis reflective collimator with a focal length of 4000 mm and an aperture of 200 mm, and its emitted beam collimation accuracy is better than 1 microradian. A beam quality analyzer was installed at the focal plane of the collimator. This analyzer uses an indium gallium arsenide (IGaAs) array detector with a pixel size of 15 micrometers and a detection wavelength coverage of 900 nm to 1700 nm. The beam quality analyzer is adjusted to the precise position of the focal plane via a precision displacement stage, with a positioning accuracy better than 5 micrometers.

[0105] The calibration personnel send commands via the control module to move the second wedge prism to a preset initial position, corresponding to the state of minimum effective optical thickness of the two wedge prisms, i.e., minimum divergence angle. The calibration personnel activate the light source module, setting the wavelength to 1550 nm and the output power to 10 mW. The beam, collimated by the double wedge prisms and aspherical mirrors, exits and enters the collimator. The collimator images the incident beam onto the focal plane, and a beam quality analyzer acquires the focal plane spot image. The calibration personnel read the spot diameter using analysis software, calculated using the second-order moment definition. Based on the spot diameter and the known focal length of the collimator, the calibration personnel calculate the current divergence angle according to geometric optics. The measurement is repeated three times, and the average value is taken as the calibration divergence angle at that position. The displacement and corresponding divergence angle at that position are recorded.

[0106] The calibration personnel send displacement commands to the slide stage driver via the control module, gradually moving the second wedge prism from its initial position towards its maximum travel. Each movement is set to a step size of 2 millimeters. After moving to a new position, the control module waits for the slide stage to stabilize completely before repeating the above-described spot acquisition and divergence angle calculation process. Starting from the initial position, the calibration personnel move sequentially to 2 millimeters, 4 millimeters, 6 millimeters, and finally to the maximum travel of 30 millimeters, completing 16 calibration points. At each calibration point, the displacement and corresponding average divergence angle are recorded. To eliminate the influence of retracement errors, after completing the forward travel calibration, the calibration personnel return point by point from the maximum travel position with the same step size to perform the reverse travel calibration. The average of the divergence angle measurements at the same position in both directions is taken as the final result.

[0107] After completing data acquisition at all calibration points, the calibration personnel obtained 16 sets of discrete data pairs of displacement and divergence angle. They imported the data into data processing software and used the least squares method to perform polynomial fitting on the discrete data. A third-order polynomial was chosen for the fitting to avoid overfitting while ensuring fitting accuracy. The fitted polynomial yielded a cubic polynomial analytical relationship between displacement and divergence angle, with a fitting residual of less than 3%. The calibration personnel wrote the obtained polynomial coefficients into the non-volatile memory of the control module as firmware parameters. Simultaneously, they also wrote a complete displacement-divergence angle lookup table into the firmware as an array, serving as a backup and verification method for the polynomial calculations.

[0108] After calibration, the calibration personnel randomly selected five calibration points for repeatability verification. Each point was measured three times, and the measurement deviation at the same location was calculated. The verification results showed that the repeatability deviation at each point was less than 2%, and the maximum deviation over the entire travel range was less than 5%, meeting the calibration accuracy requirements.

[0109] The beneficial effects of one of the embodiments in this specification include at least the following: by using a precise calibration process with a collimator and a beam quality analyzer, a precise analytical relationship between the displacement of the second wedge prism and the divergence angle of the emitted beam is established. The beneficial effect is that the fitting residual of the calibration data is less than 3% over the entire stroke range, ensuring the accuracy and consistency of the divergence angle control. At the same time, the method of writing the calibration data into the firmware allows users to avoid repeated calibration during actual use. They only need to input the target divergence angle to automatically check the target displacement and drive it into place, which greatly improves the convenience of operation and the response speed of the divergence angle setting.

[0110] In one overall embodiment, see Figure 3 The solution proposed in this application can be composed of a light source module, a double wedge prism divergence angle adjustment module, a deformable mirror turbulence simulation module, an aspherical mirror collimation module, a visible light-assisted alignment module, and a control module. The entire device is encapsulated in a precision aluminum chassis, with external dimensions not exceeding 400mm × 300mm × 200mm and a total weight not exceeding 15kg. It supports desktop placement or tripod mounting.

[0111] The light source module consists of a single-mode light source, a single-mode optical fiber, and an optical fiber mount. The single-mode light source uses a wavelength-tunable semiconductor laser (wavelength coverage: 1530nm~1570nm), with an adjustable output power of 5mW~12mW, power stability better than ±0.5% (8 hours), linewidth <0.1nm, and polarization extinction ratio >20dB. The single-mode optical fiber (mode field diameter 9~10μm@1550nm) transmits the laser from the light source to the optical fiber mount, which is mounted and fixed on the base plate.

[0112] The dual-wedge prism divergence angle adjustment module consists of a first wedge prism (fixed wedge), a second wedge prism (moving wedge), a high-precision displacement slide, and a slide driver. The two wedge prisms are arranged in series along the optical axis, and the material is fused silica. The wedge angle is designed according to the target divergence angle range (typical value 1.5mrad~5mrad). The two light-transmitting surfaces are coated with anti-reflection films (reflectivity <0.3%) corresponding to the working wavelength.

[0113] The first wedge prism is fixedly installed in the optical path, with its flat side facing the fiber optic base and its wedge-shaped side facing the second wedge prism. The second wedge prism is mounted on a high-precision displacement slide, performing precise translational motion along its inclined plane. The high-precision displacement slide is driven by a piezoelectric ceramic (PZT) or a stepper motor + ball screw, with a stroke of 10~50mm, positioning accuracy ≤1μm, and repeatability ≤0.5μm. The slide driver communicates with the host computer via USB or RS232 interface, receiving control commands and feeding back the actual position.

[0114] The deformable mirror turbulence simulation module consists of a continuous surface piezoelectric deformable mirror (PDM), a multi-channel high-voltage amplifier, and a wavefront reconstruction control algorithm. The deformable mirror employs a 61-element piezoelectric actuator array (hexagonal arrangement), with a mirror aperture D=25mm, coated with a broadband high-reflectivity dielectric film (reflectivity ≥99.5%@850~1550nm), and a resonant frequency ≥1.5kHz. The multi-channel high-voltage amplifier has an output voltage range of 0~300V, a resolution ≥12bit, and each channel is independently controllable.

[0115] The aspherical mirror collimation module consists of an off-axis parabolic mirror. The focal length is determined according to the system's exit aperture and collimation requirements (e.g., 500mm). The material is silicon carbide, and the reflectivity is ≥98% within the operating wavelength range. The light beam, after passing through the double wedge prism and deformable mirror, is incident on the aspherical mirror and collimated into parallel light or a beam with a controllable divergence angle for exit.

[0116] The visible light-assisted alignment module consists of a visible light solid-state laser. The visible light solid-state laser is a 532nm semiconductor-pumped solid-state laser (DPSS) with an output power of 1~10mW, beam quality M²<1.3, and divergence angle <1mrad. The visible light laser is fixed to the side of the device and undergoes coaxial calibration before leaving the factory to ensure that the visible light beam is coaxial with the calibration light source.

[0117] The mounting base plate provides mechanical mounting interfaces for the above modules. It is made of Invar 36 / 4J32 steel and has a good coefficient of thermal expansion.

[0118] The control module consists of a host computer (industrial panel PC or laptop) and dedicated monitoring host computer software. The host computer communicates with each subsystem via Ethernet / USB / RS232 interfaces to achieve unified and coordinated control. The monitoring host computer software is developed based on Qt and integrates functions such as divergence angle control, turbulence phase screen generation and deformable mirror driving, wavelength and power switching, visible light alignment control, and calibration process management.

[0119] Furthermore, the dual-wedge prism divergence angle adjustment module of this application changes the effective optical thickness of the two wedge prisms by precisely translating the moving wedge along the inclined plane, thereby achieving continuous adjustment of the output beam divergence angle. The core purpose of divergence angle adjustment is to enable the output beam to cover the receiving field of view of a large-aperture (>500mm) laser station receiving antenna, which is a key feature that distinguishes this device from existing small fiber optic collimators.

[0120] The principle of divergence angle adjustment is as follows: when a beam of parallel light (or approximately parallel light) passes through two series-connected wedge prisms, the propagation characteristics of the outgoing light depend on the relative positions of the two prisms. Let the wedge angle of a single wedge prism be α, and the refractive index of the material be n. The first prism (fixed wedge) is fixedly installed, with its planar side facing the incident light and its wedge-shaped side facing the second prism. The second prism (moving wedge) is mounted on a high-precision displacement slide and can be linearly translated along its inclined plane.

[0121] When the moving wedge moves a distance Δs along the inclined plane, the overlapping area of ​​the two prisms changes, which is equivalent to changing the optical thickness of a variable-thickness parallel plate. Let the equivalent thickness change caused by the movement of the inclined plane be Δt. According to geometric relationships: Δt = Δs · sin(α) Where α is the wedge angle. Changes in the equivalent thickness cause a change in the radius of curvature of the outgoing wavefront, thus achieving continuous adjustment of the divergence angle. For the collimation system with focal length f, the divergence angle... The relationship with the equivalent thickness change Δt can be approximately expressed as:

[0122] in The diameter of the beam. Let Δs be the refractive index of the wedge mirror material, and f be the focal length of the collimating lens. The equivalent thickness can be continuously adjusted by changing Δs. This allows for continuous adjustment of the divergence angle.

[0123] The core application scenario of this application is to cover the receiving antenna of a large-aperture (>500mm) laser station. The receiving antenna aperture of a ground station for satellite-to-ground laser communication is typically 500mm~2000mm, corresponding to a receiving field of view of hundreds of microradians to several milliradians. To ensure that the emitted beam from the calibration source completely covers the receiving antenna's field of view, a divergence angle is required. satisfy:

[0124] in For the receiving antenna aperture, For testing distance. For typical parameters ( =1000mm, =2000m), required divergence angle ≥0.5mrad. By selecting appropriate wedge angle α and collimation focal length f, this device can achieve a divergence angle adjustment range of 0.15mrad to 5mrad, fully covering the field of view requirements of typical ground station receiving antennas.

[0125] It should be noted that the movement of the moving wedge along the inclined plane introduces a certain lateral offset of the optical axis (typically on the order of tens to hundreds of microradians). For large-aperture (>500mm) receiving antennas, this offset is much smaller than the antenna's receiving field of view and will not significantly affect the beam coverage. During fine alignment, this offset can be eliminated through a subsequent two-step alignment process (coarse adjustment in visible light + fine adjustment based on receiver energy feedback).

[0126] The divergence angle calibration in this application was performed using a collimator and beam quality analyzer in the laboratory. The specific calibration procedure is as follows: Calibration Principle: A collimator is an optical device that produces collimated beams. Its working principle is to convert a point light source located on the focal plane into parallel light output. Conversely, when a beam of light with a certain divergence angle is incident on a collimator, it will form a spot of a certain size on its focal plane. The size of this spot is proportional to the divergence angle of the incident beam; therefore, the divergence angle of the incident beam can be calculated by measuring the size of the spot on the focal plane.

[0127] Let the focal length of the collimator be... The divergence angle of the incident beam is The diameter of the light spot on the focal plane is... The relationship with the divergence angle is:

[0128] in This is the diameter of the focal spot. This calibration scheme uses the focal length. A precision collimator with a diameter of 4000mm is used in conjunction with a beam quality analyzer to measure the focal spot size and calculate the actual divergence angle.

[0129] The calibration steps are as follows: Establish the calibration optical path. Fix this device on the precision adjustment platform, ensuring the emitted beam is incident along the optical axis of the collimator. Collimator focal length. =4000mm, with an aperture not less than the diameter of the emitted beam from this device. A beam quality analyzer is installed at the focal plane of the collimator, precisely aligned with the focal plane.

[0130] Set the initial state. Move the moving wedge of the double wedge prism to the initial position (Δs=0, corresponding to the minimum divergence angle state), turn on the single-mode light source (wavelength λ=1550nm), and set the output power to the stable value required for calibration.

[0131] Beam spot measurement and divergence angle calculation. A beam quality analyzer was used to acquire images of the focal plane beam spot, and the beam spot diameter was recorded. According to the formula Calculate the actual divergence angle corresponding to the current moving wedge position. The measurement resolution of the beam quality analyzer should be better than 0.1 mm, corresponding to a divergence angle resolution of <25 μrad. Repeat the measurement three times and take the average to reduce random error.

[0132] Multi-point calibration scan. The moving wedge is gradually moved from its initial position (Δs=0) to its maximum stroke (...). ), to fix the step size (e.g. =1mm or 2mm) at each calibration point Δs i Repeatedly measure the spot size and calculate the divergence angle, and record the moving wedge displacement Δs at each position. i and the corresponding actual divergence angle θ i .

[0133] Data processing and fitting. The obtained discrete calibration data (Δs) i , θ i Polynomial fitting is performed to establish the analytical relationship between the moving wedge displacement and the divergence angle: = f(Δs). Typically, second- or third-order polynomial fitting is used: = a0 + a1·Δs + a2·Δs² + a3·Δs³, where a0, a1, a2, and a3 are fitting coefficients. The fitting residual should be <3% to ensure the accuracy of divergence angle control throughout the entire stroke range.

[0134] Lookup table generation and writing. The fitted polynomial coefficients or the complete lookup table are written into the control software firmware of this device. In actual use, the user inputs the target divergence angle, and the software uses the lookup table or fitting formula to look up the required moving wedge displacement, driving the slide to the desired position to achieve precise divergence angle setting.

[0135] Repeatability verification. After calibration, randomly select 5-10 calibration points and repeatedly measure the actual divergence angle to verify the repeatability of the calibration results. The deviation of multiple measurements at the same location should be <2%, and the maximum deviation over the entire travel range should be <5%.

[0136] Furthermore, the deformable mirror turbulence simulation module of this application is only used to simulate wavefront phase distortion caused by atmospheric turbulence and does not involve optical axis offset compensation. The control of the deformable mirror is based on a pre-calibrated influence matrix and adopts an open-loop control method (without real-time wavefront sensor feedback), which simplifies the system structure and reduces cost and complexity.

[0137] Atmospheric turbulence in satellite-to-ground laser communication links exhibits the following characteristics: long transmission distance (400-2000 km for LEO satellites, approximately 36,000 km for GEO satellites), large zenith angle variation (0°-90°), and turbulence intensity varying with altitude (strongest near the ground, gradually weakening at higher altitudes). Equivalent Fried parameters. and equivalent Greenwood frequency, These are key parameters describing the turbulence effects of satellite-to-ground links:

[0138] = 0.427 /

[0139] in Zenith angle, The length of atmospheric coherence. This is the equivalent wind speed, typically 5~15 m / s. For a typical satellite-to-ground link, The range is 5~30cm (λ=1550nm). =0°), The range is 10~100Hz. For height, This is a profile of the refractive index structure constant, describing the turbulence intensity at various heights.

[0140] This application employs an improved power spectrum inversion method (FFT + multi-level harmonic compensation) to generate a turbulent phase screen that conforms to Kolmogorov statistical theory. The algorithm flow is as follows: Step 1: Parameter Input. The user inputs simulation scenario parameters (satellite orbital altitude, zenith angle, equivalent wind speed, etc.), and the software automatically calculates the equivalent... and .

[0141] Step 2: Power spectrum calculation. The modified von Karman power spectrum is used:

[0142] in =2π / L0 (external dimensions, L0≈10~100m). =5.92 / l0 (internal dimensions, l0≈0.01m). It is the spatial angular frequency.

[0143] Step 3: Frequency Domain Filtering and IFFT. Generate two independent standard normal distributed random matrices R1 and R2, construct a complex random field R, perform frequency domain filtering using the power spectrum, and then perform inverse Fourier transform to obtain the spatial domain phase screen φFFT(x,y).

[0144] Step 4: Subharmonic Compensation (P=3~5 layers). Set the number of subharmonic layers P, with the p-th layer in the low-frequency region. Non-uniform sampling is performed on the power spectrum to calculate the compensated phase screen. This compensates for the shortcomings of the FFT method in the low-frequency region.

[0145] in For low-frequency mode integer index, select the value that makes the frequency fall within the range of 10 ... Integer pairs within; The coefficients are complex Gaussian random numbers; These are spatial coordinates.

[0146] Step 5: Normalization and Verification. Normalization after overlay compensation: Verify the phase structure function. Compared with the theoretical value of 6.88 (r / ) 5 The compliance rate of / ³ is <10%.

[0147] Where D is the telescope aperture; The phase structure function, i.e., the phase distance The mean square value of the phase difference between the two points; The interval vector between two points; Random reference position vector.

[0148] Further, the deformable mirror driving voltage is solved: The target phase screen is mapped to the deformable mirror driving voltage using a regularized least squares method. The influence matrix A is obtained through pre-calibration (a unit voltage is applied sequentially to each actuator, and the corresponding mirror deformation is measured using an external interferometer or a Shack-Hartmann wavefront sensor; the wavefront sensor is removed after calibration). Driving voltage solution:

[0149] in =10 - ³ is the regularization parameter. Let N² be the target phase screen vector. The matrix is ​​the identity matrix. SVD decomposition is used to improve numerical stability. This scheme employs open-loop control, eliminating the need for real-time wavefront sensor feedback; the deformable mirror directly applies surface shape changes according to a pre-calculated driving voltage sequence.

[0150] To simulate the dynamic turbulence effects of the satellite-to-ground link, this application adopts the Taylor frozen turbulence assumption combined with the phase screen translation method: the generated static phase screen is translated using an equivalent wind speed. The corresponding rate is spatially shifted to simulate time evolution. The deformable mirror's kHz-level response speed can support a phase screen refresh rate of up to 500Hz, fully covering the Greenwood frequency range (10~200Hz) of the satellite-to-ground link.

[0151] This application provides a two-step coarse-fine alignment method that does not require a closed-loop wavefront monitoring system: the first step uses a visible light laser for coarse alignment, and the second step uses optical power feedback from the receiver for fine alignment. This method simplifies the system structure, eliminates the need for expensive wavefront sensors or position detectors, and reduces device cost and operational complexity.

[0152] Specifically, visible light coarse alignment includes: Visible light coarse alignment uses a 532nm green laser as a visible reference beam to achieve rapid approximate alignment between the transmitter and receiver.

[0153] Working principle: A dichroic mirror combines the green light from a visible laser (532nm) with the main optical path (near-infrared communication light) into a coaxial beam. During the assembly and adjustment phase, the visible laser is turned on, and the high visibility of the green light allows for quick determination of the direction and approximate position of the emitted beam through visual observation or monitoring with a regular CCD camera.

[0154] Operating steps: Place the laser communication terminal under test (or ground station receiving antenna) at an appropriate distance (2000m) in front of this device; turn on the visible light solid-state laser to emit a green reference beam; adjust the overall attitude (pitch / azimuth) of this device so that the green light spot is roughly located in the center area of ​​the receiving antenna under test; at the same time, adjust the pointing of the terminal under test so that its receiving field of view is facing the emission direction of this device; when the green light spot stably appears in the field of view of the receiving end, the coarse alignment is completed.

[0155] Typical accuracy for visible light coarse alignment is ±0.1 mrad (limited by human eye resolution and mechanical adjustment precision), which is sufficient to guide the beam into the field of view of a large-aperture (>500 mm) receiving antenna. For a 1000 mm aperture receiving antenna, at a test distance of 2000 m, a coarse alignment accuracy of ±0.1 mrad corresponds to a spot center offset of ±20 mm, which is well within the antenna's receiving range.

[0156] Specifically, the fine alignment of the receiver's energy feedback includes: Receiver-side energy feedback fine alignment is the core alignment method of this application. It utilizes the optical power detection capability of the receiver under test to achieve precise beam alignment by maximizing the received optical power. This method does not require additional alignment sensors or wavefront monitoring systems, and directly uses the received power of the communication link itself as the feedback signal.

[0157] Working principle: When the light beam enters the field of view of the receiving antenna, the spatial optical power meter at the receiving end can detect the incident light power. By systematically fine-tuning the pointing angle of this device or the terminal under test, and monitoring the changes in received light power in real time, the optimal alignment position that maximizes the received power can be found. This process is essentially a multi-dimensional power maximization search.

[0158] Operating procedures: After coarse alignment with visible light, turn off the visible light laser and switch to near-infrared communication light (e.g., 1550nm); enable the optical power monitoring function at the receiver under test (using its own communication receiver or an independent optical power meter) and record the received optical power in real time. The device or the terminal under test enters the scanning search mode: Centered on the coarse alignment position, it performs small-amplitude (step size 10~50μrad) scanning movements in both elevation and azimuth directions; after each step, it records the received optical power at the current position. After the search is completed, move the device / terminal to the position with the highest received power; repeat the scan search mode, gradually reducing the scan step size (from 50μrad to 5μrad) until the received power reaches a stable maximum value; record the received power at the final aligned position as the calibration reference.

[0159] Specifically, pre-shipment focusing and coaxial verification includes: During the factory inspection phase of solid-state laser communication terminals, this device can be used as a standard reference source for focusing and coaxiality verification. Focusing Verification: Turn on the visible light laser and align the device under test with this device; the internal CCD camera of the device captures an image of a green light spot; adjust the internal focusing mechanism of the device and observe the changes in the shape of the light spot; when the light spot reaches its smallest and clearest state, record the position of the focusing mechanism to complete the focus calibration. Typical changes in the light spot diameter before and after focusing: approximately 15 pixels before optimization, approximately 5 pixels after optimization.

[0160] Coaxiality verification: After focusing, check the offset of the center of the spot on the CCD relative to the center of the detector; if the offset exceeds the tolerance, adjust the terminal optical axis fine adjustment mechanism until the spot is centered; rotate the terminal under test to different azimuth angles and repeat the coaxiality check at each position to verify the coaxiality consistency of the terminal within the field of view.

[0161] This application provides a complete integrated calibration method that organically combines divergence angle adjustment, turbulence simulation, and coarse and fine alignment to achieve comprehensive testing of laser communication systems.

[0162] Specifically, PAT capture performance testing includes: Operating steps: Set the divergence angle to a typical operating value (e.g., 500 μrad to simulate LEO satellite beacon light); simulate typical turbulent conditions (e.g., moderate turbulence). =10cm); turn off the output of this device and put the terminal under test into scanning search mode; turn on the output of this device and record the time from scanning to successful capture; repeat the test more than 50 times and calculate the average capture time and capture success rate.

[0163] Specifically, communication link performance evaluation includes: Operating steps: Establish an optical link between this device and the terminal under test and complete the energy feedback alignment; set the simulated scene parameters, and the system will automatically calculate... and Communication tests were conducted under different turbulence conditions, and the bit error rate (BER) and received optical power fluctuations (scintillation index) were recorded. The results were compared and analyzed with the theoretical link budget, and a test report was generated.

[0164] In the target scenario of LEO satellite-to-ground downlink simulation calibration, the downlink laser communication link from the low Earth orbit (LEO) satellite to the ground station is simulated for calibration testing of the ground station receiving system.

[0165] Step 1: System Setup. Place this device 50m in front of the ground station being tested, secure it with a tripod, and level it. The ground station receiving antenna has a diameter of 1000mm.

[0166] Step 2: Visible Light Coarse Alignment. Turn on the visible light solid-state laser (532nm) to emit a green reference beam. Adjust the overall pitch and azimuth of the device so that the green light spot is approximately centered on the receiving antenna. After coarse alignment, the green light spot will stably appear within the field of view of the receiver.

[0167] Step 3: Fine Alignment for Energy Feedback. Turn off visible light and switch to near-infrared communication light (λ=1550nm). The ground station under test activates its optical power monitoring function. Using the coarse alignment position as the center, manually fine-tune the gimbal supporting the device in both elevation and azimuth directions, and record the received optical power in real time.

[0168] Step 4: Parameter Setting and Divergence Angle Adjustment. Adjust the divergence angle and turbulence parameters. (e.g., moderate turbulence at 12cm) (e.g., 20Hz low dynamic turbulence simulation).

[0169] Step 5: Turbulence simulation initiation. The calibration software generates a 500-frame phase screen sequence (256×256 samples), employing an FFT+3-level harmonic compensation algorithm. The driving voltage (61-element deformable mirror) is calculated and applied in open loop at a 500Hz refresh rate.

[0170] Step 6: PAT capture test. Turn the output off and on again, and record the capture time. Repeat 50 times, calculate the average capture time, and the capture success rate with turbulence on and off.

[0171] Compared with the prior art, this application has the following beneficial effects: Multifunctional integration: For the first time, four major functions, namely double wedge prism divergence angle adjustment, deformable mirror turbulence simulation, visible light-assisted alignment and aspherical collimation, are integrated into a single device, realizing comprehensive calibration of the laser communication system and avoiding the cumbersome operation and repeated positioning errors of using multiple independent devices; Wide-range divergence angle coverage: The divergence angle adjustment range of the double wedge prism can reach 0.15~5mrad, which can cover the receiving field of view of large-aperture (>500mm) laser station receiving antennas, solving the technical bottleneck that existing small collimators cannot cover large-aperture antennas; Two-step alignment without closed-loop wavefront monitoring: The two-step alignment strategy of "coarse alignment with visible light + fine adjustment with receiver energy feedback" simplifies the system structure, reduces cost and operational complexity, and achieves alignment accuracy on the order of 10 μrad. Quantitative turbulence simulation: Based on the FFT+subharmonic compensation algorithm of Kolmogorov theory and the accurate deformable mirror driven mapping method, and using an open-loop control mode, quantitative control of turbulence intensity (r0 deviation <5%, structure function deviation <10%) is achieved, which can qualitatively and quantitatively simulate various atmospheric conditions for satellite-to-ground communication. Visible light-assisted alignment: Integrating a 532nm green laser as an alignment reference solves the problem of assembly and adjustment difficulties caused by the invisibility of near-infrared light, and supports pre-shipment focusing and coaxial verification of solid-state laser communication terminals and rapid on-site alignment; Portable field deployment: The overall size is ≤400mm×300mm×200mm and the weight is ≤15kg. It supports tabletop placement or tripod installation and is suitable for various scenarios such as laboratory testing, field calibration and emergency communication support.

[0172] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments in this specification are not limited to the described order of actions, because according to the embodiments in this specification, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the embodiments in this specification.

[0173] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0174] The preferred embodiments disclosed above are merely illustrative of this specification. The optional embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the embodiments described herein. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the embodiments, thereby enabling those skilled in the art to better understand and utilize this specification. This specification is limited only by the claims and their full scope and equivalents.

Claims

1. A portable laser communication far-field calibration source device, characterized in that, include: The light source module is used to generate laser light in the communication band. The double wedge prism divergence angle adjustment module is disposed after the light source module along the optical path. It includes a first wedge prism and a second wedge prism that can be translated along the inclined plane direction. The divergence angle of the emitted beam is adjusted by changing the inclined plane displacement of the second wedge prism. The deformable mirror turbulence simulation module is set after the double wedge prism divergence angle adjustment module along the optical path. It includes a deformable mirror and a high voltage amplifier. The deformable mirror receives a driving voltage to change the mirror surface shape and apply wavefront phase distortion to the beam to simulate atmospheric turbulence effects. The aspherical mirror collimation module is positioned after the deformable mirror turbulence simulation module along the optical path, collimating the beam after divergence angle adjustment and turbulence simulation into parallel light or a beam with controllable divergence angle for emission. A visible light-assisted alignment module includes a visible light laser, wherein the visible light emitted by the visible light laser is coaxial with the communication band laser emitted by the light source module, and is used to assist in coarse alignment; The control module is communicatively connected to the double wedge prism divergence angle adjustment module, the deformable mirror turbulence simulation module, and the visible light-assisted alignment module for unified and coordinated control.

2. The portable laser communication far-field calibration source device according to claim 1, characterized in that, The double wedge prism divergence angle adjustment module also includes a high-precision displacement slide and a slide driver. The second wedge prism is mounted on the high-precision displacement slide. The high-precision displacement slide is driven by a piezoelectric ceramic or by a stepper motor and a ball screw. The slide driver is communicatively connected to the control module, receives displacement commands, and feeds back the actual position.

3. The portable laser communication far-field calibration source device according to claim 1, characterized in that, The deformable mirror is a continuous surface piezoelectric deformable mirror, comprising a 61-unit piezoelectric actuator array arranged in a hexagonal pattern, with a mirror aperture of 25mm and coated with a broadband high reflectivity dielectric film. The high voltage amplifier is a multi-channel high voltage amplifier, with each channel independently controllable, an output voltage range of 0 to 300V, and a resolution of not less than 12 bits.

4. The portable laser communication far-field calibration source device according to claim 1, characterized in that, The visible light laser in the visible light-assisted alignment module is a 532nm semiconductor-pumped solid-state laser. The visible light laser is fixed to the side of the device and is coaxially aligned to ensure that the visible light is coaxial with the emitted beam of the light source module.

5. The portable laser communication far-field calibration source device according to claim 1, characterized in that, The aspherical mirror collimation module includes an off-axis parabolic mirror, which is made of silicon carbide.

6. A calibration method implemented using the portable laser communication far-field calibration source device according to any one of claims 1 to 5, characterized in that, Includes the following steps: The portable laser communication far-field calibration source device is placed in front of the laser communication terminal under test, and fixed and leveled by a tripod; The visible light-assisted alignment module is activated, a visible reference beam is emitted, and the overall attitude of the portable laser communication far-field calibration source device is adjusted so that the visible light spot is located in the center area of ​​the receiving antenna of the laser communication terminal under test, thus completing the coarse alignment. Turn off the visible light-assisted alignment module, switch to the communication band laser emission of the light source module, turn on the optical power monitoring function of the laser communication terminal under test, and record the received optical power in real time; Using the coarse alignment position as the center, the portable laser communication far-field calibration source device or the laser communication terminal under test is scanned stepwise in the pitch and azimuth directions. The current received optical power is recorded with each step. The pointing position is moved to the point of maximum received power to complete fine alignment. The control module sets the target divergence angle, and the control module looks up the target displacement of the second wedge prism based on the pre-stored calibration data, and drives the second wedge prism to move to the target position so that the divergence angle of the emitted beam covers the receiving field of view of the receiving antenna. The control module sets the simulation scene parameters, generates a turbulent phase screen that conforms to Kolmogorov statistical theory, calculates the driving voltage sequence of the deformable mirror, applies the driving voltage sequence to the deformable mirror, causes the deformable mirror to produce a corresponding surface shape change, applies wavefront phase distortion to the beam, and simulates atmospheric turbulence effects. The scanning and capture mode of the laser communication terminal under test is turned on, the output of the portable laser communication far-field calibration source device is turned on, the time from the start of scanning to successful capture is recorded, the process is repeated multiple times, and the average capture time and capture success rate are calculated.

7. The calibration method according to claim 6, characterized in that, In the fine alignment step, the scanning step size is gradually reduced from 50 μrad to 5 μrad until the received power reaches a stable maximum value. The received power at the final alignment position is recorded as the calibration reference.

8. The calibration method according to claim 6, characterized in that, The generation of the turbulent phase screen employs a power spectrum inversion method combined with subharmonic compensation, specifically including: Input the simulation scenario parameters, which include satellite orbital altitude, zenith angle, ground refractive index structure constant and equivalent wind speed, and calculate the equivalent Fried parameter and equivalent Greenwood frequency; Frequency domain filtering was performed using a modified von Karman power spectrum, and the initial phase screen was obtained by inverse Fourier transform. Subharmonic sampling is performed in the low-frequency region to generate a compensated phase screen. The compensated phase screen is then superimposed on the initial phase screen to obtain the target phase screen. Verify the consistency between the phase structure function of the target phase screen and the theoretical value. If the deviation is less than 10%, the target phase screen is confirmed to be effective.

9. The calibration method according to claim 8, characterized in that, The solution of the driving voltage sequence includes: obtaining a pre-calibrated deformable mirror influence matrix, which is obtained by sequentially applying a unit voltage to each driver and measuring the corresponding mirror deformation; using regularized least squares method to solve the driving voltage vector based on the target phase screen and the influence matrix, wherein the driving voltage vector is improved in numerical stability by singular value decomposition; and applying an open-loop surface change to the deformable mirror according to the solved driving voltage vector.

10. The calibration method according to claim 6, characterized in that, The calibration data is obtained in advance through the following steps: the portable laser communication far-field calibration source device is fixed on a precision adjustment platform, so that the emitted beam is incident along the optical axis of the collimator, and a beam quality analyzer is installed at the focal plane position of the collimator; the second wedge prism is moved to the initial position, the focal plane spot diameter is measured, and the current divergence angle is calculated; the second wedge prism is gradually moved from the initial position to the maximum stroke, and the actual divergence angle is repeatedly measured at each calibration point with a fixed step size, and the displacement and corresponding actual divergence angle of each calibration point are recorded; polynomial fitting is performed on the obtained discrete calibration data to establish an analytical relationship between the displacement and the divergence angle, and the polynomial coefficients obtained by fitting or the complete displacement-divergence angle lookup table is written into the firmware of the control module.

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