A turbulent channel multimode field beam generation and fiber coupling test system

Abstract

The present invention relates to the field of space laser communication, and in particular to providing a turbulent channel multimode field beam generation and fiber coupling test system, comprising a laser emission and test module, a fundamental mode optical transmission module, at least two high-order mode optical modulation modules, and a spatial light combining module. The laser emission and test module is used to emit a fundamental mode beam coupled to the fundamental mode optical transmission module and each high-order mode optical modulation module. The fundamental mode optical transmission module is used to collimate the incident fundamental mode beam and transmit it to the spatial light combining module. Each high-order mode optical modulation module is used to perform high-order mode modulation on the incident fundamental mode beam and transmit it to the spatial light combining module. The spatial light combining module is used to couple each high-order mode beam and the fundamental mode beam into the same optical fiber, thereby achieving simultaneous and parallel coupling of multiple modes of spatial light with the optical fiber. The present invention can achieve simultaneous and parallel coupling of different modes of spatial light with the optical fiber, thereby achieving verification of the high-order mode communication effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of space laser communications, and in particular relates to a turbulent channel multimode field beam generation and optical fiber coupling test system. Background Art

[0002] Improving the coupling efficiency between spatial light and optical fibers is a key issue in space laser communications. However, during the alignment process, mode conversion occurs due to angle mismatch in the incident light. This leads to multimode interference and intermodal dispersion, signal distortion, and increased additional loss, ultimately impacting communication performance. With the ever-increasing demand for transmission rates and distances, angle mismatch is unavoidable, and the fundamental mode beam can branch into multiple higher-order modes. However, the impact of this on communication performance is difficult to assess.

[0003] Therefore, there is an urgent need for a test system for coupling multi-mode spatial light with optical fibers to simulate turbulent channels. Summary of the Invention

[0004] In view of this, the present invention aims to provide a turbulent channel multimode field beam generation and fiber coupling test system, which simulates different modes of spatial light to couple with the optical fiber at different incident angles to provide a basis for analyzing the impact of angle mismatch on communication effects.

[0005] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0006] A turbulent channel multimode field beam generation and fiber coupling test system includes a laser emission and test module, a fundamental mode light transmission module, at least two high-order mode light modulation modules and a spatial light combining module; wherein,

[0007] The laser emission and testing module is used to emit fundamental mode beam;

[0008] Each high-order mode light modulation module includes a high-order mode light collimator, a beam expander, a polarizer, a beam splitter and a spatial light modulator;

[0009] The fundamental mode light transmission module includes a fundamental mode light collimator;

[0010] The spatial photosynthesis module includes a fast mirror and a mixed-mode light collimator;

[0011] The fundamental mode beam emitted by the laser emission and test module is coupled to the fundamental mode optical transmission module and each high-order mode optical modulation module respectively. In each high-order mode optical modulation module, the fundamental mode beam is sequentially collimated by the high-order mode light collimator, expanded by the beam expander, polarized by the polarizer, and transmitted by the beam splitter, and is vertically incident on the spatial light modulator for high-order mode modulation of the target order. The modulated high-order mode beam is reflected back to the beam splitter, and then sequentially reflected by the beam splitter and the fast reflector to be incident on the mixed mode light collimator. In the fundamental mode optical transmission module, the fundamental mode beam is sequentially collimated by the fundamental mode light collimator, transmitted by each beam splitter, and is incident on the mixed mode light collimator. The fundamental mode beam and high-order mode beams of different orders are coupled into the same optical fiber through the mixed mode light collimator to form a composite mode beam.

[0012] Furthermore, the laser emission and testing module includes a laser, a communication coherent transceiver and an optical fiber splitter, and the communication coherent transceiver includes a modulation module, a demodulation module and a mixing module; the communication light emitted by the laser is divided into two paths by the optical fiber splitter and incident on the communication coherent transceiver, one path is used as local oscillator light, and the other path is used as signal light. The signal light is modulated into a fundamental mode light beam by the modulation module and coupled into each high-order mode light collimator and the fundamental mode light collimator respectively; the local oscillator light and the composite mode light beam enter the mixing module, and the mixed signal output after mixing by the mixing module enters the demodulation module for demodulation.

[0013] Furthermore, the laser emission and test module also includes a bit error meter, and the demodulated mixed signal enters the bit error meter after photoelectric conversion to measure the bit error rate.

[0014] Furthermore, the spatial photosynthesis module also includes a control box, through which the fast mirror receives control instructions, and by controlling the amplitude voltage loaded on the azimuth axis and pitch axis of the fast mirror, adjusts the direction of the reflecting surface of the fast mirror and changes the angle of the incident light of the mixed mode light collimator.

[0015] Furthermore, when the control instruction is a vibration simulation instruction, the control box simulates the coupling effect of vibration on the composite mode light beam by loading a random amplitude voltage with Gaussian distribution characteristics on the azimuth axis and pitch axis of the fast reflection mirror.

[0016] Furthermore, the spatial light modulator modulates the fundamental mode light beam into higher-order modes of different orders by loading higher-order mode phase distribution diagrams of different orders.

[0017] Furthermore, the expression of the eigensolution of the field component transmitted inside the optical fiber is:

[0018] ;

[0019] in, is the transverse electric field distribution, and is the transverse propagation constant, is the core radius, is the Bessel function, is the Hank function, is the order of the Bessel function, The first order Bessel function The solution is expressed as , is the radial distance in the cylindrical coordinate system, is the azimuth in the cylindrical coordinate system, is the height in cylindrical coordinates, is the time variable, is the longitudinal propagation constant, is the angular frequency, is an imaginary unit;

[0020] By changing and The transverse electric field distribution of different order high-order modes is calculated by the value of ;

[0021] The transverse electric field distribution of different-order high-order modes is calculated according to the phase angle function, and the phase distribution diagram corresponding to the transverse electric field distribution of each order high-order mode is obtained.

[0022] Furthermore, the spectroscope is an energy spectroscope with a splitting ratio of 50:50.

[0023] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0024] (1) The present invention can realize the flexible modulation of multiple types and orders of high-order mode beams and the simultaneous coupling of composite mode beams with optical fibers, thereby realizing the simulation of the coupling of multi-mode spatial light and optical fibers in turbulent channels.

[0025] (2) By controlling the voltage applied to the fast mirror and adjusting the direction of the fast mirror's reflection surface, the coupling simulation of the composite mode light beam with the optical fiber at different incident angles can be realized. Based on the simulation results, the influence of angle mismatch on the coupling efficiency during the coupling process can be analyzed, providing an experimental basis for the calculation of spatial light-fiber coupling efficiency for long-distance and high-speed communications.

[0026] (3) The setting of the beam splitter allows the light beam to be incident vertically on the spatial light modulator, avoiding the modulation effect of the spatial light modulator being affected by an excessively large incident angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 This is a structural diagram of a turbulent channel multimode field beam generation and fiber coupling test system according to an embodiment of the present invention;

[0029] Figure 2 A high-order mode phase diagram of a linear polarization mode according to an embodiment of the present invention is created;

[0030] Figure 3 Another high-order mode phase diagram of the linear polarization mode described in the embodiment of the present invention is created;

[0031] Figure 4 The spatial light modulator described in the embodiment of the present invention is based on Figure 2 The optical field distribution diagram of the linear polarization mode after the high-order mode phase pattern is modulated as shown;

[0032] Figure 5 The spatial light modulator described in the embodiment of the present invention is based on Figure 3 The optical field distribution diagram of the linear polarization mode after the high-order mode phase pattern is modulated as shown;

[0033] Figure 6 This is the original light field distribution diagram that has not been modulated by the spatial light modulator as described in the embodiment of the present invention.

[0034] Explanation of the reference numerals: laser 101, optical fiber splitter 102, communication coherent transceiver 103, bit error meter 104, modulation module 105, demodulation module 106, mixing module 107, fundamental mode light collimator 201, first high-order mode light collimator 202, first beam expander 203, first polarizer 204, first beam splitter 205, first spatial light modulator 206, second high-order mode light collimator 207, second beam expander 208, second polarizer 209, second beam splitter 210, second spatial light modulator 211, fast reflection mirror 301, mixed mode light collimator 302, control box 303. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, features defined as "first", "second" and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art can understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0039] The present invention provides a turbulent channel multimode field beam generation and fiber coupling test system, comprising a laser emission and test module, a fundamental mode optical transmission module, at least two high-order mode optical modulation modules and a spatial light combining module. The laser emission and test module is used to emit communication light and modulate it into a fundamental mode optical beam, which is coupled to the fundamental mode optical transmission module and each high-order mode optical modulation module. The fundamental mode optical transmission module is used to collimate and transmit the incident fundamental mode optical beam. Each high-order mode optical modulation module is used to perform high-order mode modulation and transmission on the incident fundamental mode optical beam. The high-order mode optical beams modulated by each high-order mode optical modulation module and the fundamental mode optical beam converge at the spatial light combining module. The spatial light combining module is used to couple the high-order mode optical beams modulated by each high-order mode optical modulation module and the fundamental mode optical beam into the same optical fiber, thereby realizing simultaneous and parallel coupling of multiple modes of spatial light and the optical fiber.

[0040] The present invention can increase or decrease the number of high-order mode light modulation modules according to the actual needs of the test system. The following example uses two high-order mode light modulation modules to achieve simultaneous and parallel coupling of three modes of spatial light with the optical fiber. For other numbers of high-order mode light modulation modules, the coupling method with the optical fiber can be obtained in a similar manner.

[0041] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0042] like Figure 1 As shown, the present invention provides a turbulent channel multimode field beam generation and fiber coupling test system, including a laser emission and test module, a fundamental mode optical transmission module, a first high-order mode optical modulation module, a second high-order mode optical modulation module and a spatial optical beam combining module; wherein the laser emission and test module includes a laser 101, an optical fiber splitter 102, a communication coherent transceiver 103 and a bit error meter 104, the communication coherent transceiver 103 includes a modulation module 105, a demodulation module 106 and a mixing module 107, the laser 1 The output pigtail of 01 is directly connected to the input port of the optical fiber splitter 102, one output port of the optical fiber splitter 102 is connected to the input port of the modulation module 105 through an optical fiber, the other output port of the optical fiber splitter 102 is connected to the input port of the mixing module 107 through an optical fiber, the output port of the mixing module 107 is connected to the input port of the demodulation module 106 through an optical fiber, and the output port of the demodulation module 106 is connected to the bit error detector 104 through an optical fiber; the fundamental mode optical transmission module includes a fundamental mode optical collimator 201, a fundamental mode optical The collimator 201 is connected to the output port of the modulation module 105 through an optical fiber; the first high-order mode light modulation module includes a first high-order mode light collimator 202, a first beam expander 203, a first polarizer 204, a first beam splitter 205, and a first spatial light modulator 206, and the first high-order mode light collimator 202 is connected to the output port of the modulation module 105 through an optical fiber; the second high-order mode light modulation module includes a second high-order mode light collimator 207, a second beam expander 208, a second polarizer 209, a second beam splitter 201 and a second spatial light modulator 206. 10 and the second spatial light modulator 211, the second high-order mode light collimator 207 is connected to the output port of the modulation module 105 through an optical fiber; the spatial light combining module includes a fast mirror 301, a mixed mode light collimator 302 and a control box 303, the control box 303 is used to control the voltage loaded to the fast mirror 301, the mixed mode light collimator 302 is set in the reflection direction of the fast mirror 301, the mixed mode light collimator 302 is connected to the head end of the optical fiber, and the tail end of the optical fiber is connected to the input port of the mixing module 107.

[0043] The communication light emitted by the laser 101 is divided into two paths by the optical fiber splitter 102 and incident on the communication coherent transceiver 103. One path is used as the local oscillator light, which enters the mixing module 107; the other path is used as the signal light. The signal light is modulated into the fundamental mode light beam by the modulation module 105 and then divided into three paths, which are respectively incident on the fundamental mode light collimator 201, the first high-order mode mode light collimator 202 and the second high-order mode mode light collimator 207. The fundamental mode light collimator 201 collimates the incident fundamental mode light beam into spatial light. The spatial light emitted by the fundamental mode light collimator 201 is transmitted through the first beam splitter 205 and the second beam splitter 210 and is incident on the fast mirror 301. It is reflected by the fast mirror 301 to the mixed mode light collimator 302 and is mixed. The first high-order mode light collimator 202 collimates the incident fundamental mode light beam into spatial light, and the spatial light emitted by the first high-order mode light collimator 202 is amplified by the first beam expander 203 to fully cover the target surface of the first spatial light modulator 206; the spatial light after beam expansion is incident on the first polarizer 204 with adjustable fast axis direction for polarization, and the spatial light is modulated into linearly polarized light. The linearly polarized light is transmitted by the first beam splitter 205 and incident on the target surface of the first spatial light modulator 206, and the incident fundamental mode light beam is modulated by the first spatial light modulator 206 after loading the high-order mode phase diagram. The modulated first high-order mode light beam is reflected back to the first beam splitter. The light beam from the first beam splitter 205 is reflected by the first beam splitter 205 and transmitted by the second beam splitter 210, and is incident on the fast mirror 301. The light beam is reflected by the fast mirror 301 to the mixed mode light collimator 302 and is received by the mixed mode light collimator 302. The second high-order mode light collimator 207 collimates the incident fundamental mode light beam into spatial light. The spatial light emitted by the second high-order mode light collimator 207 is amplified by the second beam expander 208 to fully cover the target surface of the second spatial light modulator 211. The spatial light after beam expansion is incident on the second polarizer 209 with adjustable fast axis direction for polarization, and the spatial light is modulated into linearly polarized light. The linearly polarized light is transmitted by the second beam splitter 210 and is incident on the second spatial light modulator 211. The target surface of the modulator 211 modulates the incident fundamental mode beam by loading a high-order mode phase pattern through the second spatial light modulator 211. The modulated second high-order mode beam is reflected back to the second beam splitter 210, reflected by the second beam splitter 210 and incident on the fast mirror 301. It is then reflected by the fast mirror 301 to the mixed mode light collimator 302 and received by the mixed mode light collimator 302. At this point, the three modes of spatial light (the fundamental mode beam, the first high-order mode beam, and the second high-order mode beam) converge at the mixed mode light collimator 302 and are uniformly coupled into the same optical fiber through the mixed mode light collimator 302 to form a composite mode beam, thereby achieving simultaneous and parallel coupling of the three modes of spatial light with the optical fiber.

[0044] Since all three modes of spatial light reach the quick mirror 301, control instructions can be transmitted to the quick mirror 301 through the computer's ARM program via the downloader connected to the control box 303. By controlling the amplitude voltage loaded on the azimuth and pitch axes of the quick mirror 301, the reflecting surface of the quick mirror 301 is controlled to produce precise directional deflection, thereby changing the angle of the incident light entering the mixed-mode light collimator 302. For every unit change in the amplitude voltage, the incident angle of the light beam changes by 50 μrad, realizing the analysis of the mismatch between the spatial light and the optical fiber coupling angle.

[0045] When the control instruction is a vibration simulation instruction, the control box 303 loads a random amplitude voltage with Gaussian distribution characteristics on the azimuth axis and pitch axis of the fast reflection mirror 301. This mechanism uses the principle of statistical distribution to effectively simulate the coupling effect of vibration on the composite mode light beam, analyze the degree to which the composite mode light beam can withstand different vibration amplitudes, and explore the communication quality of the measurement system under different vibration amplitudes.

[0046] The composite mode light beam enters the mixing module 107 through the optical fiber, and is mixed with the local oscillator light in the mixing module 107 to form a four-way mixed signal. The four-way mixed signal is demodulated by the demodulation module 106, and finally sent to the bit error meter 104 for bit error rate measurement after photoelectric conversion. The bit error rate measured by the bit error meter 104 can be used to analyze the impact of high-order mode fields of different modes on the communication process.

[0047] The first high-order mode light collimator 202 and the second high-order mode light collimator 207 load high-order mode phase patterns of two different target orders to modulate and generate high-order mode beams of two different target orders.

[0048] According to the waveguide field equation of the optical fiber long straight circular symmetric weak waveguide and the continuous boundary conditions, the expression of the eigensolution of the field component transmitted inside the optical fiber can be obtained as follows:

[0049] ;

[0050] in, is the transverse electric field distribution, and is the transverse propagation constant, is the core radius, is the Bessel function, is the Hank function, is the order of the Bessel function, The first order Bessel function The solution is expressed as , is the radial distance in the cylindrical coordinate system, is the azimuth in the cylindrical coordinate system, is the height in cylindrical coordinates, is the time variable, is the longitudinal propagation constant, is the angular frequency, Is an imaginary unit.

[0051] according to r and The transverse electric field distribution is calculated by changing and The transverse electric field distribution of different-order high-order modes is obtained by calculating the value of , and the transverse electric field distribution of different-order high-order modes is calculated according to the phase angle function to obtain the phase distribution diagram corresponding to the transverse electric field distribution of each order high-order mode, which is loaded onto the corresponding spatial light modulator to realize the modulation of different-order high-order modes.

[0052] The high-order phase diagram of the linear polarization mode is loaded on the spatial light modulator in the above manner to simulate the mode conversion caused by the angle mismatch of the incident light in turbulent multi-channel space laser communication. The high-order modes generated by mode aliasing and crosstalk are mixed to explore the impact of mode aliasing on communication performance.

[0053] When more high-order mode light modulation modules are used, the high-order mode light beam modulated by each high-order mode light modulation module is incident on the fast reflection mirror 301 and reflected by the fast reflection mirror 301 to the mixed mode light collimator 302 .

[0054] In a specific example of the present invention, the laser uses a laser that outputs 1550nm communication light; the signal light rate emitted by the communication coherent transceiver is 10Gbps; the fundamental mode light collimator 201 and the high-order mode light collimator use double-glued large-aperture fiber collimators, and the diameter of the output light spot is 7.9mm; the beam expander uses a fixed-magnification achromatic beam expander based on the Galilean structure, and its magnification is 2X. The diameter of the light spot emitted by the double-glued large-aperture fiber collimator reaches about 15.8mm after passing through the beam expander; the working wavelength of the polarizer is 11 00nm-1630nm, and is installed on a rotating adjustment frame to adjust the polarization direction of the incident light so that it is parallel to the polarization direction of the liquid crystal molecules inside the spatial light modulator to achieve the best modulation effect; the beam splitter uses an energy beam splitter with a splitting ratio of 50:50 and an operating band of 1100nm-1600nm; the spatial light modulator uses the X13138 series reflective silicon liquid crystal spatial light modulator (LCOS-SLM) of Hamamatsu Photonics Co., Ltd., and the phase map resolution that can be loaded in the supporting control software is , the target size of the spatial light modulator is The beam after expansion can fully cover the target surface to achieve modulation of various high-order modes, such as linear polarization mode, Hermite-Gauss mode and Laguerre-Gauss mode.

[0055] For example:l =1, m=2 when the high-order mode phase diagram is as follows Figure 2 As shown, the light field distribution of the linear polarization mode modulated after the high-order mode phase image is loaded into the spatial light modulator is as follows: Figure 4 As shown; l =3, m=1 when the high-order mode phase diagram is as follows Figure 3 As shown, the light field distribution of the linear polarization mode modulated after the high-order mode phase image is loaded into the spatial light modulator is as follows: Figure 5 As shown; the original light field distribution without spatial light modulator modulation is as follows Figure 6 shown.

[0056] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0057] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A turbulent channel multimode field beam generation and fiber coupling test system, characterized in that: It includes a laser emission and testing module, a fundamental mode light transmission module, at least two high-order mode light modulation modules and a spatial light combining module; wherein, The laser emission and testing module is used to emit fundamental mode beam; Each high-order mode light modulation module includes a high-order mode light collimator, a beam expander, a polarizer, a beam splitter and a spatial light modulator; The fundamental mode light transmission module includes a fundamental mode light collimator; The spatial photosynthesis module includes a fast mirror and a mixed-mode light collimator; The fundamental mode beam emitted by the laser emission and test module is coupled to the fundamental mode optical transmission module and each high-order mode optical modulation module respectively. In each high-order mode optical modulation module, the fundamental mode beam is sequentially collimated by the high-order mode light collimator, expanded by the beam expander, polarized by the polarizer, and transmitted by the beam splitter, and is vertically incident on the spatial light modulator for high-order mode modulation of the target order. The modulated high-order mode beam is reflected back to the beam splitter, and then sequentially reflected by the beam splitter and the fast reflector to be incident on the mixed mode light collimator. In the fundamental mode optical transmission module, the fundamental mode beam is sequentially collimated by the fundamental mode light collimator, transmitted by each beam splitter, and is incident on the mixed mode light collimator. The fundamental mode beam and high-order mode beams of different orders are coupled into the same optical fiber through the mixed mode light collimator to form a composite mode beam.

2. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 1, characterized in that: The laser emission and testing module includes a laser, a communication coherent transceiver and an optical fiber splitter. The communication coherent transceiver includes a modulation module, a demodulation module and a mixing module. The communication light emitted by the laser is divided into two paths by the optical fiber splitter and incident on the communication coherent transceiver, one path serving as the local oscillator light and the other as the signal light. The signal light is modulated into a fundamental mode beam by the modulation module and coupled into each high-order mode light collimator and the fundamental mode light collimator respectively. The local oscillator light and the composite mode beam enter the mixing module. The mixed signal output after mixing by the mixing module enters the demodulation module for demodulation.

3. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 2, characterized in that: The laser emission and test module also includes a bit error meter. The demodulated mixed signal enters the bit error meter after photoelectric conversion to measure the bit error rate.

4. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 1, characterized in that: The spatial photosynthesis module also includes a control box, through which the fast mirror receives control instructions. By controlling the amplitude voltage loaded on the azimuth axis and pitch axis of the fast mirror, the direction of the reflection surface of the fast mirror is adjusted to change the angle of the incident light of the mixed mode light collimator.

5. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 4, characterized in that: When the control instruction is a vibration simulation instruction, the control box simulates the coupling effect of vibration on the composite mode light beam by loading a random amplitude voltage with Gaussian distribution characteristics on the azimuth axis and pitch axis of the fast reflection mirror.

6. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 1, characterized in that: The spatial light modulator modulates the fundamental mode beam into higher-order modes of different orders by loading higher-order mode phase distribution patterns of different orders.

7. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 6, characterized in that: The expression of the eigensolution of the field component transmitted inside the optical fiber is: ； in, is the transverse electric field distribution, and is the transverse propagation constant, is the core radius, is the Bessel function, is the Hank function, is the order of the Bessel function, The first order Bessel function The solution is expressed as , is the radial distance in the cylindrical coordinate system, is the azimuth in the cylindrical coordinate system, is the height in cylindrical coordinates, is the time variable, is the longitudinal propagation constant, is the angular frequency, is an imaginary unit; By changing and The transverse electric field distribution of different order high-order modes is calculated by the value of ; The transverse electric field distribution of different-order high-order modes is calculated according to the phase angle function, and the phase distribution diagram corresponding to the transverse electric field distribution of each order high-order mode is obtained.

8. The turbulent channel multimode field beam generation and fiber coupling test system according to claim 1, characterized in that: The spectrometer is an energy spectrometer with a splitting ratio of 50:50.

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