Free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system

Abstract

The invention provides a free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system, which comprises a modulation module used for generating and outputting multiple paths of modulation optical signals; and the on-chip optical phased array is used for regulating and controlling the phases of the multiple paths of modulated optical signals so as to control the light beam characteristics of the multiple paths of optical signals emitted to the free space. According to the free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system based on the optical phased array chip, the size of the system is remarkably reduced, the flexibility and the precision are improved, efficient signal multiplexing, signal diversity and dynamic adjustment are achieved in multiple dimensions, and the communication rate, the communication quality and the system adaptability are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical communication, and in particular, relates to a free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system. Background Art

[0002] Traditional wireless communications rely on electromagnetic waves to propagate in the air. Due to the limitations of radio spectrum resources, its bandwidth is limited, resulting in low data rates. In addition, terrain, weather, and electromagnetic interference in complex environments further affect the quality of communication. In contrast, free space optical communication (FSO) uses lasers to propagate in free space, which has the advantages of higher frequency, larger bandwidth, and resistance to electromagnetic interference, thereby providing higher data transmission rates and is suitable for high-speed, large-capacity data transmission. Due to its low latency, high bandwidth, unlicensed spectrum, and anti-interference characteristics, FSO technology has shown broad application prospects in satellite communications, terrestrial communications, data center interconnection, military communications, and emergency communications.

[0003] However, traditional FSO systems usually rely on large optical components, precision lenses and servo motors to achieve beam shaping and directional transmission, which makes the system bulky, complex, expensive, and requires strict maintenance. At the same time, in order to achieve higher transmission rates and more stable transmission quality, multi-dimensional multiplexing systems (phase multiplexing, amplitude multiplexing, code division multiplexing, time division multiplexing, wavelength division multiplexing, space division multiplexing, polarization multiplexing and mode division multiplexing systems) and multi-dimensional diversity systems (phase diversity, amplitude diversity, code division diversity, time diversity, frequency diversity, space diversity, polarization diversity, and mode diversity) are widely used. They require multiple groups of FSO systems to simultaneously transmit multiple wavelengths, multiple polarizations and multiple modes of laser signals in multiple directions and multiple angles at the same transmitting site, which will further increase the size, cost and complexity of the system.

[0004] Therefore, in scenarios such as satellite communications and drone communications that have strict requirements on space, power consumption and integration, traditional FSO systems are often difficult to implement or have limited performance. With the development of miniaturization and integration technology, on-chip integration technology provides new possibilities for future miniaturized and integrated multi-dimensional multiplexing and multi-dimensional diversity FSO systems. However, there are many technical challenges in integrating large optical components and servo motors in traditional FSO onto chips. For example, the miniaturization integration of optical components (such as lenses, reflectors and fiber couplers) has high precision requirements and it is difficult to maintain good optical performance in small sizes; and precision drive systems such as servo motors are difficult to integrate in chip-level integration. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system based on an optical phased array (OPA) chip.

[0006] According to one aspect of the present invention, a free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system is provided, which includes: a modulation module, used to generate and output n modulated optical signals; an on-chip optical phased array, used to receive the n modulated optical signals and adjust the phase of each modulated optical signal so that the beam characteristics of each modulated optical signal are changed.

[0007] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the on-chip optical phased array is further used to adjust the initial phase of each modulated optical signal to achieve beam shaping, directional transmission, high-order mode generation and multiplexing of each modulated optical signal.

[0008] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the on-chip optical phased array includes a first optical coupler, n on-chip thermal phase shifters, and a grating array; the first optical coupler is used to receive n modulated optical signals, and transmit each modulated optical signal to the corresponding on-chip thermal phase shifter; the i-th on-chip thermal phase shifter is used to receive the i-th modulated optical signal, and change the phase of the i-th modulated optical signal so that the beam characteristics of the i-th modulated optical signal are changed, 1≤i≤n; the grating array is used to transmit each modulated optical signal with changed beam characteristics into free space.

[0009] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the n on-chip thermal phase shifters are further used to change the directional angle of each modulated optical signal in the horizontal direction when a voltage is applied thereto.

[0010] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the modulation module includes n lasers, n Mach-Zehnder modulators, and an optical coupler, the i-th Mach-Zehnder modulator is connected to the corresponding i-th laser, 1≤i≤n, and the n Mach-Zehnder modulators are all connected to the optical coupler; the n lasers are used to generate n optical carriers with different wavelengths; the i-th Mach-Zehnder modulator is used to receive a communication data signal and an i-th optical carrier, and modulate the received communication data signal onto the i-th optical carrier to form an i-th modulated optical signal.

[0011] In an example of the free-space optical multidimensional multiplexing and multidimensional diversity communication system provided in the above aspect, the modulation module also includes n first optical amplifiers, and the i-th first optical amplifier is connected between the corresponding i-th laser and the i-th Mach-Zehnder modulator.

[0012] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the directional angle of each modulated optical signal in the vertical direction is changed by changing the frequency of each optical carrier.

[0013] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system further includes: a receiving module for receiving modulated optical signals with changed characteristics of each light beam.

[0014] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the receiving module includes: n optical antennas, n de-patterning multiplexers, n receivers, and n oscilloscopes; the i-th optical antenna is used to receive the modulated optical signal whose optical beam characteristics are changed, the i-th de-patterning multiplexer is used to convert the i-th modulated optical signal of a high-order mode received by the i-th optical antenna into the i-th modulated optical signal of a low-order mode, the i-th receiver is used to demodulate the i-th modulated optical signal, and the i-th oscilloscope is used to sample the demodulated i-th modulated optical signal.

[0015] In an example of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system provided in the above aspect, the receiving module also includes: n second optical amplifiers, and the i-th second optical amplifier is arranged between the i-th de-mode multiplexer and the i-th receiver.

[0016] Beneficial effects: The present invention provides a free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system based on an optical phased array (OPA) chip. Unlike the traditional mechanical scanning method, the optical phased array chip does not require any moving parts. The OPA chip is composed only of an on-chip optical phase shifter array and a grating array. By adjusting the on-chip optical phase shifter array, the phase distribution of multi-wavelength light beams at the grating array can be quickly and accurately adjusted, and then the direction, wavefront and propagation characteristics of these light beams can be adjusted, and finally multi-directional, multi-angle, multi-wavelength, multi-polarization and multi-mode laser signal beam shaping, emission and transmission are realized. The OPA chip has the ability of beamforming and wavefront compensation, which also improves the system's adaptability to atmospheric disturbances and signal transmission quality.

[0017] In addition, by combining the optical phased array with the free-space optical multi-dimensional multiplexing technology, and utilizing the optical phased array chip's ability to precisely control light beams and the high transmission capacity of the multi-dimensional multiplexing technology, the system can simultaneously transmit multi-wavelength, multi-polarization, and multi-mode light beams in multiple directions and angles, and significantly improve the system's transmission capacity through multiplexing technology; by combining the optical phased array with the free-space optical multi-dimensional diversity technology, and utilizing the optical phased array chip's ability to precisely control light beams and the redundancy of the diversity technology, the system can simultaneously transmit multi-wavelength, multi-polarization, and multi-mode light beams in multiple directions and angles, and significantly improve the reliability of the communication system through signal redundancy.

[0018] Furthermore, the proposed system not only meets the scenarios with high space and power consumption requirements such as satellite communication and UAV communication, but also can effectively cope with channel fading and dynamic environmental interference, and enhance the transmission rate, robustness and anti-interference ability of the system in multi-path and multi-wavelength signal transmission.

[0019] Therefore, the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system based on optical phased array chips has greatly improved the communication rate, quality and system adaptability by significantly reducing the system volume, improving flexibility and accuracy, and realizing efficient signal multiplexing, signal diversity and dynamic adjustment in multiple dimensions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other aspects, features and advantages of the embodiments of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0021] Figure 1 is a principle structure diagram of a free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to an embodiment of the present invention;

[0022] Figure 2 It is a diagram of experimental test results of a free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to an embodiment of the present invention for an optical signal with a specified optical mode, emission angle, polarization state, wavelength, baud rate and phase amplitude multiplexing modulation format. DETAILED DESCRIPTION

[0023] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention may be implemented in many different forms, and the present invention should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and their practical applications, so that other persons skilled in the art can understand the various embodiments of the present invention and various modifications suitable for specific intended applications.

[0024] As used herein, the term "including" and its variations represent open terms, meaning "including but not limited to". The terms "based on", "according to", etc. mean "based at least in part on", "based at least in part on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other definitions may be included below, whether explicit or implicit. Unless the context clearly indicates otherwise, the definition of a term is consistent throughout the specification.

[0025] Figure 1 It is a principle structure diagram of a free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to an embodiment of the present invention.

[0026] Reference Figure 1 According to an embodiment of the present invention, the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system includes: a modulation module 5, used to generate and output n modulated optical signals; an on-chip optical phased array 9, used to receive n modulated optical signals and adjust the phase of each modulated optical signal so that the beam characteristics of each modulated optical signal are changed.

[0027] In another embodiment, the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to the embodiment of the present invention further includes: a receiving module RM, which is used to receive modulated optical signals with changed characteristics of each light beam.

[0028] Specifically, the modulation module 5 includes: a laser 11 . . . a laser 1 n , a Mach-Zehnder modulator 21 . . . a Mach-Zehnder modulator 2 n , an optical amplifier 31 . . . an optical amplifier 3 n , and an optical coupler 4 .

[0029] Laser 11 . . . laser 1n respectively generate and output n optical carriers with different wavelengths.

[0030] The i-th Mach-Zehnder modulator 2i is used to receive a communication data signal (which is provided externally, such as a microwave signal) and an i-th optical carrier output by the i-th laser 1i, and modulate the received communication data signal onto the i-th optical carrier to form an i-th modulated optical signal, where 1≤i≤n. Each Mach-Zehnder modulator operates at a minimum bias point (i.e., a null point).

[0031] The i-th optical amplifier 3i is used to receive the i-th modulated optical signal and amplify the i-th modulated optical signal. Of course, if the signal strength of the i-th modulated optical signal is strong enough, in another embodiment, the optical amplifiers may not exist.

[0032] The optical coupler 4 is used to couple the modulated optical signals amplified by the optical amplifiers 31 . . . 3n to an optical waveguide (eg another optical coupler).

[0033] In addition, the on-chip optical phased array 9 includes an optical coupler 6 , on-chip thermal phase shifters 71 . . . 7 n , and a grating array 8 .

[0034] The optical coupler 6 is used to evenly transmit the energy of the modulated optical signal from the modulation module 5 to each on-chip thermal phase shifter, and the modulated optical signals of all frequencies will arrive in front of each on-chip thermal phase shifter.

[0035] The i-th on-chip thermal phase shifter 7i is used to receive the i-th modulated optical signal and change the phase of the i-th modulated optical signal so that the beam characteristics of the i-th modulated optical signal are changed. Here, the on-chip thermal phase shifters 71...7n constitute an on-chip optical phase shifter array, which is used to realize phase compensation and flexible adjustment of the initial phase of the modulated optical signal when it is emitted from the grating array 8. In a specific embodiment, the on-chip thermal phase shifter is realized by using a silicon waveguide and a heating plate, but the present invention is not limited to this.

[0036] The grating array 8 is used to transmit each modulated optical signal with changed beam characteristics into free space. In a specific embodiment, a grating array with a grating spacing of 2 um is used.

[0037] That is to say, in the on-chip optical phased array 9, by adjusting the on-chip optical phase shifter array, the phase distribution of the multi-wavelength modulated optical signal at the grating array 8 can be quickly and accurately adjusted, and then the direction, wavefront and propagation characteristics of these modulated optical signals can be adjusted to achieve beam shaping, emission and transmission of multi-directional, multi-angle, multi-wavelength, multi-polarization and multi-mode laser modulated optical signals. The on-chip optical phased array 9 has the ability of beam forming and wavefront compensation, thereby improving the system's adaptability to atmospheric disturbances and signal transmission quality.

[0038] Continue to refer to Figure 1 , the grating array 8 emits light beams (i.e., modulated light signals with changed characteristics of each beam) 101...10n. Due to the interference behavior of the wavefront, these light beams have some characteristics. For example, by changing the voltage on the on-chip thermal phase shifter, the phase distribution of the light beam at the time of emission can be changed, and beam shaping, high-order mode light generation and horizontal direction angle adjustment of the light beam can be further realized; by changing the frequency of the optical carrier, the direction angle of the light beam in the vertical direction can be changed rapidly, thereby realizing rapid vertical steering, etc.

[0039] In some examples, the initial phase of each modulated optical signal at the grating array 8 is adjusted by an on-chip optical phase shifter array to To achieve wavefront interference and focusing shaping of the light beam; by changing the voltage applied to the on-chip optical phase shifter array, the directional angle of the focused and shaped light beam can be changed rapidly in the horizontal direction to achieve rapid horizontal steering; by changing the frequency of the optical carrier through the modulation module 5 (such as a laser), the directional angle of the light beam in the vertical direction can be changed rapidly, thereby achieving rapid vertical steering of the light beam; the multi-directional, multi-angle, and multi-wavelength rapid response functions here provide technical support for wavelength division multiplexing and space division multiplexing.

[0040] Furthermore, through polarization multiplexing, the transmission capacity can be further increased exponentially. By loading a specific phase distribution through an on-chip optical phase shifter array, high-order mode beams can be generated, such as the first-order or higher-order modes of the Laguerre-Gaussian beam in the orbital angular momentum beam. The multiplexing of these high-order mode beams can still further improve the transmission capacity. The fast response function of the multi-polarization, multi-mode beams here provides technical support for polarization multiplexing and mode division multiplexing.

[0041] Furthermore, when the modulation module 5 modulates the optical signal, time division multiplexing is achieved by flexibly allocating the transmission time periods occupied by different communication data. At the same time, different coherent modulation methods can be selected, such as 16QAM, 64QAM, 256QAM, 1024QAM, etc., so as to achieve phase and amplitude multiplexing of the optical signal (if the phase and amplitude multiplexing technologies are selectively allocated, code division multiplexing can also be achieved).

[0042] At the same time, if the signals modulated in multiple multiplexing channels are the same replica signal, a free-space optical multi-dimensional diversity system can be realized. By utilizing the redundancy of diversity technology, the reliability of the communication system can be significantly improved.

[0043] In summary, this paper explains how the free-space optical multidimensional multiplexing and multidimensional diversity communication system based on optical phased array chips can realize phase multiplexing, amplitude multiplexing, code division multiplexing, time division multiplexing, wavelength division multiplexing, space division multiplexing, polarization multiplexing and mode division multiplexing, as well as the corresponding diversity technologies.

[0044] Continue to refer to Figure 1 The receiving module RM includes an optical antenna 111...11n, a demultiplexer 121...12n, an optical amplifier 131...13n, a receiver 141...14n, and an oscilloscope 151...15n.

[0045] The i-th optical antenna 11i is used to receive the modulated optical signal with the i-th optical beam characteristic changed. In one example, the optical antenna may be composed of an aspherical optical lens, which can effectively receive the optical signal.

[0046] The i-th de-mode multiplexer 12i is used to convert the i-th modulated optical signal of the high-order mode received by the i-th optical antenna into the i-th modulated optical signal of the low-order mode. In one example, the de-mode multiplexer is composed of a spatial light modulator or other similar functional devices, which can convert the high-order mode optical signal into the low-order mode optical signal.

[0047] The i-th optical amplifier 13i is used to receive the i-th modulated optical signal and amplify the i-th modulated optical signal. Of course, if the signal strength of the i-th modulated optical signal is strong enough, in another embodiment, the optical amplifiers may not exist.

[0048] The i-th receiver 14i is used to demodulate the i-th modulated optical signal.

[0049] The i-th oscilloscope 15i is used to sample the demodulated i-th modulated optical signal for subsequent digital signal processing.

[0050] In a specific embodiment, 8 wavelengths of optical signals are obtained through coherent modulation. These optical signals realize wavefront shaping, high-order mode beam generation and emission of optical signals on the optical phased array chip. At the same time, by changing the configuration voltage of the optical phased array chip, the optical signal can be quickly turned and scanned in the horizontal direction. By changing the frequency value of the 8 wavelengths, the optical signal can be quickly turned and scanned in the vertical direction, realizing wavelength division multiplexing, mode division multiplexing and space division multiplexing. By using different modulation methods, such as multi-order phase modulation (8-PSK, etc.), multi-order amplitude modulation (8-ASK, etc.), coherent modulation (16QAM, etc.), phase multiplexing, amplitude multiplexing and code division multiplexing of optical signals are realized; by modulating different signals in different time periods, time division multiplexing of optical signals is realized; by configuring optical signals of multiple polarization states in the optical phased array chip, polarization multiplexing of optical signals is realized; by loading the same copy information in each multiplexing technology, the same multi-dimensional diversity technology can be realized.

[0051] In the experiment, the above optical signal was transmitted through a 20m free space link, received by the optical antenna and demodulated without error at the receiver. The experimental test results of the optical signal with the specified optical mode, emission angle, polarization state, wavelength (1550nm), baud rate (20Gbaud) and phase amplitude multiplexing modulation format (coherent modulation format: 16QAM) are as follows Figure 2 See Figure 2 ,The measured EVM = 10.5% and error-free communication results verify the ,effectiveness of the proposed system.

[0052] In summary, the potential and capabilities of the system in phase multiplexing, amplitude multiplexing, code division multiplexing, time division multiplexing, wavelength division multiplexing, space division multiplexing, polarization multiplexing and mode division multiplexing, as well as the corresponding diversity are explained and verified. Furthermore, the basic principles and architecture of the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system based on optical phased array chips are fully explained and verified. By combining the optical phased array with free-space optical multi-dimensional multiplexing technology, using the precise control beam capability of the optical phased array chip and the high transmission capacity capability of the multi-dimensional multiplexing technology, the system can simultaneously transmit multi-wavelength, multi-polarization and multi-mode beams in multiple directions and angles, and significantly improve the system transmission capacity through multiplexing technology; by combining the optical phased array with free-space optical multi-dimensional diversity technology, using the precise control beam capability of the optical phased array chip and the redundancy of the diversity technology, the system can simultaneously transmit multi-wavelength, multi-polarization and multi-mode beams in multiple directions and angles, and significantly improve the reliability of the communication system through signal redundancy.

[0053] In addition, the proposed system not only meets the requirements of satellite communications, drone communications and other scenarios with high space and power consumption requirements, but also can effectively cope with channel fading and dynamic environmental interference, and enhance the system's transmission rate, robustness and anti-interference ability in multi-path and multi-wavelength signal transmission. Furthermore, the free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system based on optical phased array chips significantly reduces the system volume, improves flexibility and accuracy, and realizes efficient signal multiplexing, signal diversity and dynamic adjustment in multiple dimensions (the eight dimensions proposed in the architecture are only examples), greatly improving the communication rate, quality and system adaptability. Furthermore, the system is expected to play an important role in future high-bandwidth, low-latency communication applications such as satellite communications, drone communications, and 5G and 6G networks.

[0054] The optional implementation modes of the embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above implementation modes. Within the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all belong to the protection scope of the embodiments of the present invention.

Claims

1. A free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system, characterized in that: The free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system comprises: A modulation module, used for generating and outputting n modulated optical signals; The on-chip optical phased array is used to receive n modulated optical signals and adjust the phase of each modulated optical signal so that the beam characteristics of each modulated optical signal emitted into free space are changed.

2. The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 1, characterized in that: The on-chip optical phased array is further used to adjust the initial phase of each modulated optical signal to achieve beam shaping, directional transmission, high-order mode generation and multiplexing of each modulated optical signal.

3. The free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 1 or 2, characterized in that: The on-chip optical phased array comprises a first optical coupler, n on-chip thermal phase shifters, and a grating array; The first optical coupler is used to receive n modulated optical signals and transmit each modulated optical signal to a corresponding on-chip thermal phase shifter; The i-th on-chip thermal phase shifter is used to receive the i-th modulated optical signal and change the phase of the i-th modulated optical signal so that the beam characteristics of the i-th modulated optical signal are changed, 1≤i≤n; The grating array is used to transmit each modulated optical signal with changed beam characteristics into free space.

4. The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 3, characterized in that: The n on-chip thermal phase shifters are further used to change the direction angle of each modulated optical signal in the horizontal direction when a voltage is applied thereto.

5. The free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 1 or 2, characterized in that: The modulation module includes n lasers, n Mach-Zehnder modulators, and an optical coupler, the i-th Mach-Zehnder modulator is connected to the corresponding i-th laser, 1≤i≤n, and the n Mach-Zehnder modulators are all connected to the optical coupler; The n lasers are used to generate n optical carriers with different wavelengths; The i-th Mach-Zehnder modulator is used to receive a communication data signal and an i-th optical carrier, and modulate the received communication data signal onto the i-th optical carrier to form an i-th modulated optical signal.

6. The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 5, characterized in that: The modulation module further includes n first optical amplifiers, and the i-th first optical amplifier is connected between the corresponding i-th laser and the i-th Mach-Zehnder modulator.

7. The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 5, characterized in that: By changing the frequency of each optical carrier, the directional angle of each modulated optical signal in the vertical direction is changed.

8. The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 1 or 2, characterized in that: The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system further comprises: a receiving module for receiving modulated optical signals with changed characteristics of each optical beam.

9. The free-space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 8, characterized in that: The receiving module includes: n optical antennas, n de-mode multiplexers, n receivers, and n oscilloscopes; The i-th optical antenna is used to receive the i-th modulated optical signal with changed optical beam characteristics, the i-th de-mode multiplexer is used to convert the i-th modulated optical signal of a high-order mode received by the i-th optical antenna into the i-th modulated optical signal of a low-order mode, the i-th receiver is used to demodulate the i-th modulated optical signal, and the i-th oscilloscope is used to sample the demodulated i-th modulated optical signal for subsequent digital signal processing.

10. The free space optical multi-dimensional multiplexing and multi-dimensional diversity communication system according to claim 9, characterized in that: The receiving module further includes: n second optical amplifiers, and the i-th second optical amplifier is arranged between the i-th de-mode multiplexer and the i-th receiver.

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