Optical wireless obstacle avoidance communication system and method
By using bottle-like light beams in the optical wireless communication system to bypass obstacles, and combining coherent light and Airy ring Fourier transform technology, the problem of optical wireless communication being susceptible to obstacles is solved, achieving high capacity and stable communication.
Patent Information
- Application Number
- CN202510235981.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2025-06-03
AI Technical Summary
Existing optical wireless communications are susceptible to obstacles, resulting in power loss or communication interruption, while spatial optical modulators can only respond to a single polarization, limiting communication capacity.
The bottle-like beam is used to bypass obstacles, and through the combination of coherent light emission, obstacle avoidance system and coherent receiving end, the bottle-like beam is generated by using the Airy ring Fourier transform to improve communication capacity.
It realizes stable transmission of the optical wireless communication system when encountering obstacles, and improves communication capacity, supporting point-to-multipoint air separation obstacle avoidance function.
Smart Images
Figure CN120090712A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of optical wireless obstacle avoidance communication, and particularly to an optical wireless obstacle avoidance communication system and method. Background Art
[0002] In recent years, optical wireless communication has become a core technology in the field of 6G communication. Compared with microwave communication, it has characteristics such as a high bandwidth exceeding 2000 THz, high confidentiality brought by a narrow beam width, and low cost due to the absence of spectrum authorization. Compared with fiber optic communication, it is flexibly and simply deployed, can be reinstalled, does not require the cost of dedicated fiber optic connections, and can achieve various communication methods such as point-to-point and point-to-multipoint. Therefore, as an extended technology of microwave communication and fiber optic communication, optical wireless communication has great research potential and broad application space.
[0003] However, current optical wireless communication is extremely susceptible to the influence of obstacles, resulting in power loss or even communication interruption. At the same time, most existing optical wireless communications use a spatial light modulator to control the light beam, and the spatial light modulator can only respond to a single polarization, which undoubtedly limits the communication capacity. Summary of the Invention
[0004] This application provides an optical wireless obstacle avoidance communication system and method, which uses a bottle-shaped light beam to bypass obstacles in space and can also improve the communication capacity.
[0005] In a first aspect, an embodiment of this application provides an optical wireless obstacle avoidance communication system, and the optical wireless obstacle avoidance communication system includes:
[0006] A coherent optical transmitter, which is used to coherently modulate a transmission signal into optical carriers of multiple wavelengths, combine the modulated multiple optical signals into one beam, and output linearly polarized light after polarizing the combined optical signal;
[0007] An obstacle avoidance system, which is used to convert the linearly polarized light into circularly polarized light and perform phase reconstruction based on the Fourier transform of the Airy ring to generate a bottle-shaped light beam;
[0008] A coherent optical receiver, which is used to couple the bottle-shaped light beam into an optical fiber for coherent demodulation to demodulate the transmission signal.
[0009] In combination with the first aspect, in an implementation, the obstacle avoidance system includes:
[0010] A quarter-wave plate, which is used to convert the linearly polarized light into left-handed circularly polarized light or right-handed circularly polarized light;
[0011] A metasurface, which performs phase reconstruction on the left-handed circularly polarized light or right-handed circularly polarized light based on the Fourier transform of the Airy ring;
[0012] The first lens, which enables the beam after phase reconstruction to generate a bottle beam at the focal plane.
[0013] Combined with the first aspect, in one embodiment, the obstacle avoidance system further includes:
[0014] The second lens, which is used to focus the propagated bottle beam.
[0015] Combined with the first aspect, in one embodiment, the metasurface is a geometric phase liquid crystal metasurface, and the micro-nano unit of the geometric phase liquid crystal metasurface includes silicon substrates distributed on both sides, and an alignment film and a liquid crystal layer located between the two silicon substrates.
[0016] Combined with the first aspect, in one embodiment, the phase distribution of the metasurface is the phase distribution after Fourier transform of the Airy ring, where the complex amplitude expression of the Airy ring is: where Ai is the Airy function, r 0 (θ) is the polar coordinate expression of the ring shape, r is the polar distance, θ is the polar angle, w is the scaling factor, and a is the attenuation factor.
[0017] Combined with the first aspect, in one embodiment, the coherent optical transmitter includes:
[0018] A tunable laser, which is used to output lasers of multiple wavelengths as optical carriers;
[0019] Multiple first polarization controllers, the number of which corresponds to the number of wavelengths, and are used to adjust the polarization state of each laser beam to be the same;
[0020] Multiple modulators, the number of which corresponds to the number of wavelengths, and are used to modulate the transmitted signal onto the optical carrier;
[0021] A wavelength division multiplexer, which is used to combine the multiplexed modulated optical signals into one beam;
[0022] A second polarization controller, which is used to output linearly polarized light after polarizing the combined optical signal.
[0023] Combined with the first aspect, in one embodiment, the tunable laser is a tunable laser in the infrared band and is used to output lasers of four wavelengths in the infrared band.
[0024] Combined with the first aspect, in one embodiment, the coherent optical transmitter further includes:
[0025] A first collimator, which is used to collimate the output linearly polarized light output by the second polarization controller.
[0026] Combined with the first aspect, in one embodiment, the coherent optical receiver includes:
[0027] A second collimator for coupling the bottle-shaped beam into an optical fiber;
[0028] An amplifier for amplifying the power of the bottle-shaped beam coupled into the optical fiber;
[0029] A filter for filtering out the out-of-band noise of the amplified bottle-shaped beam;
[0030] A coherent demodulation device for coherently demodulating the bottle-shaped beam after filtering out the out-of-band noise to demodulate the transmitted signal.
[0031] In a second aspect, an optical wireless obstacle avoidance communication method provided by an embodiment of the present application includes:
[0032] At a coherent optical transmitter, coherently modulating a transmitted signal onto optical carriers of multiple wavelengths, combining the modulated multiple optical signals into a single beam, and outputting linearly polarized light after polarizing the combined optical signal;
[0033] Using an obstacle avoidance system to convert the linearly polarized light into circularly polarized light and performing phase reconstruction based on the Fourier transform of the Airy ring to generate a bottle-shaped beam;
[0034] At a coherent receiver, coupling the bottle-shaped beam into an optical fiber for coherent demodulation to demodulate the transmitted signal.
[0035] The beneficial effects brought by the technical solution provided by the embodiment of the present application include:
[0036] The optical wireless obstacle avoidance communication system in the present application includes a coherent optical transmitter, an obstacle avoidance system, and a coherent receiver. At the coherent optical transmitter, coherently modulating a transmitted signal onto optical carriers of multiple wavelengths, combining the modulated multiple optical signals into a single beam, and outputting linearly polarized light after polarizing the combined optical signal; using the obstacle avoidance system to convert the linearly polarized light into circularly polarized light and performing phase reconstruction based on the Fourier transform of the Airy ring to generate a bottle-shaped beam; at the coherent receiver, coupling the bottle-shaped beam into an optical fiber for coherent demodulation to demodulate the transmitted signal.
[0037] The present application uses coherent light and a metasurface to modulate two polarization states of a beam. In order to further improve the communication capacity, wavelength division multiplexing technology is also adopted to modulate multiple beams of different wavelengths in the infrared band. In addition, multiple bottle-shaped beams are used to bypass obstacles in space, realizing the space division obstacle avoidance function from point to multi-point. Description of the Drawings
[0038] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.
[0039] Figure 1 It is a structural block diagram of an embodiment of the optical wireless obstacle avoidance communication system of the present application;
[0040] Figure 2 It is a schematic diagram of the liquid crystal metasurface micro-nano unit of the present application;
[0041] Figure 3 It is a schematic diagram of the double Airy ring arrangement of the present application;
[0042] Figure 4 It is a schematic diagram of the phase after Fourier transform of the double Airy ring of the present application;
[0043] Figure 5 It is a schematic diagram of the propagation process of the double bottle-shaped beam of the present application;
[0044] Figure 6 It is a schematic diagram of the light intensity of the double bottle-shaped beam after propagating a certain distance of the present application;
[0045] Figure 7 It is a flowchart of an embodiment of the optical wireless obstacle avoidance communication method of the present application. Detailed implementation manners
[0046] In order to enable those skilled in the art to better understand the solutions of the present application, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.
[0047] To make the purpose, technical solutions and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the accompanying drawings.
[0048] In a first aspect, an embodiment of the present application provides a free space optical communication system.
[0049] In one embodiment, with reference to Figure 1 , Figure 1 It is a structural block diagram of an embodiment of the optical wireless obstacle avoidance communication system of the present application. As Figure 1 shown, the optical wireless obstacle avoidance communication system includes a coherent optical transmitter, an obstacle avoidance system, and a coherent optical receiver.
[0050] Among them, a coherent optical transmitter is used to coherently modulate a transmitted signal into optical carriers of multiple wavelengths, combine the modulated multiplexed optical signals into one beam, and output linearly polarized light after polarizing the combined optical signal; an obstacle avoidance system is used to convert the linearly polarized light into circularly polarized light and perform phase reconstruction based on the Fourier transform of the Airy ring to generate a bottle-shaped beam; a coherent receiver is used to couple the bottle-shaped beam into an optical fiber for coherent demodulation to demodulate the transmitted signal.
[0051] Specifically, the coherent optical transmitter Tx includes: a tunable laser, multiple first polarization controllers, multiple modulators, a wavelength division multiplexer, and a second polarization controller.
[0052] Among them, the tunable laser is used to output lasers of multiple wavelengths as optical carriers; the number of first polarization controllers corresponds to the number of wavelengths and is used to adjust the polarization state of each laser beam to be the same; the number of modulators corresponds to the number of wavelengths and is used to modulate the transmitted signal onto the optical carrier; the wavelength division multiplexer is used to combine the modulated multiplexed optical signals into one beam; the second polarization controller is used to output linearly polarized light after polarizing the combined optical signal.
[0053] Preferably, in one embodiment, the coherent optical transmitter includes a tunable laser in the infrared band, four first polarization controllers, four modulators, a wavelength division multiplexer, a second polarization controller, an erbium-doped fiber amplifier, and a first collimator. As Figure 1 shown, the tunable laser outputs lasers of four wavelengths in the infrared band (in this embodiment, four lasers with a wavelength near 1550 nm and an interval of 100 GHz are taken as an example). After each laser beam is adjusted to have the same polarization state by the first polarization controller, the required signal (in this embodiment, a 25 Gb / s 16-QAM signal is taken as an example) is coherently modulated onto the optical carrier at the modulator. The four modulated optical signals are combined into one optical signal through the wavelength division multiplexer, amplified by the erbium-doped fiber amplifier, adjusted to linear polarization by the second polarization controller, and then collimated by the first collimator. Then, the light beam is incident into free space. It should be noted that the optical signals in Tx are all transmitted in the optical fiber.
[0054] The obstacle avoidance system includes: a quarter-wave plate, a metasurface, and a first lens.
[0055] The quarter-wave plate is used to convert the linearly polarized light into left-handed circularly polarized light or right-handed circularly polarized light; the metasurface performs phase reconstruction on the left-handed circularly polarized light or right-handed circularly polarized light based on the Fourier transform of the Airy ring; the first lens enables the phase-reconstructed light beam to generate a bottle-shaped beam at the focal plane.
[0056] Preferably, in one embodiment, the obstacle avoidance system includes a quarter-wave plate, a metasurface, a first lens, and a second lens. AsFigure 1 As shown in the figure, the linearly polarized light is converted into left-handed circularly polarized light after passing through a quarter-wave plate and is incident on the designed metasurface. The light beam whose phase is reconstructed by the metasurface generates a bottle-shaped beam at the focal plane after passing through the first lens. Here, the first lens plays the role of Fourier transform. If there is an obstacle smaller than the bottle body at the focal plane, the optical bottle can bypass it without being blocked. Finally, the bottle-shaped beam is focused by the second lens and enters the second collimator for coupling with the optical fiber. It should be noted that all the optical signals in the obstacle avoidance system are transmitted in free space. It should be noted that when the included angle between the incident linearly polarized direction and the fast axis of the wave plate is -45°, the outgoing light is left-handed circularly polarized light, and when the included angle between the incident linearly polarized direction and the fast axis of the wave plate is 45°, the outgoing light is right-handed circularly polarized light. Both left-handed circularly polarized light and right-handed circularly polarized light can be used to implement the solution in this application, but the same liquid crystal metasurface can only meet the requirements of one circularly polarized light incident. It should be noted that all the optical signals in the obstacle avoidance system are transmitted in free space.
[0057] There are several design methods for the metasurface, such as transmission phase, geometric phase, and resonance phase. In this application, the geometric phase liquid crystal metasurface is taken as an example. The liquid crystal metasurface uses liquid crystal molecules with a sandwich structure unit as micro-nano units, as Figure 2 shown. This micro-nano unit usually includes silicon substrates distributed on both sides, an alignment film, and a liquid crystal layer in the middle. The liquid crystal metasurface has an accurate and continuous phase adjustment ability. By adjusting the long-axis orientation angle γ of the liquid crystal molecules, a phase shift of 2γ / -2γ can be generated (corresponding to left-handed circularly polarized light and right-handed circularly polarized light incident respectively), so as to achieve a complete 2π multi-level phase shift.
[0058] The phase distribution of the metasurface uses the phase distribution after the Fourier transform of the Airy ring. In order to perform spatial division multiplexing on the light beam and achieve point-to-multipoint transmission, multiple Airy rings need to be arranged on the same plane and then Fourier-transformed uniformly to obtain the required phase. The complex amplitude of a single Airy ring satisfies: where Ai is the Airy function, r 0 (θ) is the polar coordinate expression of the ring shape, r is the polar distance, θ is the polar angle, w is the scaling factor, and a is the attenuation factor. In this embodiment, taking two Airy rings arranged left and right as an example, as Figure 3 shown, where the left one is a square Airy ring and the right one is a circular Airy ring. The phase obtained after the unified Fourier transform is as Figure 4 shown.
[0059] The size and shape of the bottle body can be realized by changing the r 0 (θ) expression. In particular, if the shape of the bottle body is not circular, w in the complex amplitude of the Airy ring needs to be rewritten as to ensure that light rays at different angles can be focused at the same point, where f is the focal length and k is the wave vector.
[0060] The propagation process of the bottle-shaped beam is as follows Figure 5 shown. The upper side is a square bottle body, and the lower side is a circular bottle body. The dotted line represents the position of the lens. As the propagation distance increases, the bottle body of the bottle-shaped beam will gradually close and finally evolve into a Bessel-like beam. The light intensity after it propagates a certain distance is as follows Figure 6 shown.
[0061] Applying the Rayleigh-Sommerfeld diffraction formula to calculate the complex amplitude of the Airy ring propagating forward / backward for a certain distance, and then performing a Fourier transform on the complex amplitude to obtain the phase can change the position of the optical bottle body.
[0062] The coherent receiving end includes: a second collimator, an amplifier, a filter, and a coherent demodulation device.
[0063] The second collimator is used to couple the bottle-shaped beam into the optical fiber; the amplifier is used to amplify the power of the bottle-shaped beam coupled into the optical fiber; the filter is used to filter out the out-of-band noise of the amplified bottle-shaped beam; the coherent demodulation device is used to perform coherent demodulation on the bottle-shaped beam after filtering out the out-of-band noise to demodulate the transmitted signal.
[0064] Preferably, in one embodiment, the coherent receiving end Rx includes a second collimator, an erbium-doped fiber amplifier, a band-pass filter, and a subsequent coherent demodulation device. The beam is coupled into a single-mode optical fiber through the second collimator, amplified by the erbium-doped fiber amplifier, and enters the coherent demodulation device after the out-of-band noise is filtered out by the band-pass filter to demodulate the transmitted signal. It should be noted that all the optical signals in Rx are transmitted in the optical fiber.
[0065] Based on the above description, in order to overcome the problems in the prior art, in this application, an obstacle-avoiding optical wireless communication system based on metasurface is proposed, which uses coherent light and metasurface to modulate two polarization states of the beam. In order to further improve the communication capacity, wavelength division multiplexing technology is also adopted to modulate four beams with different wavelengths in the infrared band. In addition, multiple bottle-shaped beams are used to bypass obstacles in space, realizing the space division obstacle-avoiding function from point to multi-point.
[0066] In summary, the optical wireless obstacle-avoiding communication system in this application includes a coherent optical transmitting end, an obstacle-avoiding system, and a coherent receiving end. At the coherent optical transmitting end, the transmitted signal is coherently modulated into optical carriers of multiple wavelengths, and the multiplexed optical signals after modulation are combined into one beam, and the combined optical signal is output as linearly polarized light after polarization; the obstacle-avoiding system is used to convert the linearly polarized light into circularly polarized light and perform phase reconstruction based on the Fourier transform of the Airy ring to generate a bottle-shaped beam; at the coherent receiving end, the bottle-shaped beam is coupled into the optical fiber for coherent demodulation to demodulate the transmitted signal.
[0067] This application uses coherent light and a metasurface to modulate two polarization states of a light beam. To further improve the communication capacity, wavelength division multiplexing technology is also adopted to modulate light beams of multiple different wavelengths in the infrared band. In addition, multiple bottle-shaped light beams are used to bypass obstacles in space, realizing a space division obstacle avoidance function from point to multi-point.
[0068] In a second aspect, an embodiment of this application provides a polarization-independent spatial light obstacle avoidance method.
[0069] In one embodiment, referring to Figure 7 , Figure 7 is a flowchart of an embodiment of the polarization-independent spatial light obstacle avoidance method of this application. As shown in Figure 7 , the polarization-independent spatial light obstacle avoidance method includes:
[0070] S1. At the coherent light transmitting end, the transmitted signal is coherently modulated into optical carriers of multiple wavelengths, and the multiplexed optical signals after modulation are combined into one beam, and the combined optical signal is polarized and then linearly polarized light is output;
[0071] S2. The obstacle avoidance system is used to convert the linearly polarized light into circularly polarized light, and phase reconstruction is performed based on the Fourier transform of the Airy ring to generate a bottle-shaped light beam;
[0072] S3. At the coherent receiving end, the bottle-shaped light beam is coupled into an optical fiber for coherent demodulation to demodulate the transmitted signal.
[0073] Further, in one embodiment, a quarter-wave plate is used to convert the linearly polarized light into left-handed circularly polarized light or right-handed circularly polarized light;
[0074] The metasurface is used to perform phase reconstruction on the left-handed circularly polarized light or right-handed circularly polarized light based on the Fourier transform of the Airy ring;
[0075] A first lens is used to make the light beam after phase reconstruction generate a bottle-shaped light beam at the focal plane.
[0076] Further, in one embodiment, a second lens is also used to focus the propagated bottle-shaped light beam.
[0077] Further, in one embodiment, the metasurface is a geometric phase liquid crystal metasurface, and the micro-nano unit of the geometric phase liquid crystal metasurface includes silicon substrates distributed on both sides, and an alignment film and a liquid crystal layer located between the two silicon substrates.
[0078] Further, in one embodiment, the phase distribution of the metasurface is the phase distribution after the Fourier transform of the Airy ring, where the complex amplitude expression of the Airy ring is: where Ai is the Airy function, r 0($\theta$) is the polar coordinate expression of an annular shape, $r$ is the polar distance, $\theta$ is the polar angle, $w$ is the scaling factor, and $a$ is the attenuation factor.
[0079] Further, in one embodiment, a tunable laser is used to output lasers of multiple wavelengths as optical carriers;
[0080] Multiple first polarization controllers corresponding to the number of wavelengths are used to adjust the polarization states of each laser beam to be the same;
[0081] Modulators corresponding to the number of wavelengths are used to modulate the transmission signal onto the optical carrier;
[0082] A wavelength division multiplexer is used to combine the multiple modulated optical signals into one beam;
[0083] A second polarization controller is used to output linearly polarized light after polarizing the combined optical signal.
[0084] Further, in one embodiment, the tunable laser is a tunable laser in the infrared band and is used to output lasers of four wavelengths in the infrared band.
[0085] Further, in one embodiment, a first collimator is used to collimate the output linearly polarized light output by the second polarization controller.
[0086] Further, in one embodiment, a second collimator is used to couple the bottle-shaped beam into an optical fiber;
[0087] An amplifier is used to amplify the power of the bottle-shaped beam coupled into the optical fiber;
[0088] A filter is used to filter out the out-of-band noise of the amplified bottle-shaped beam;
[0089] A coherent demodulation device is used to perform coherent demodulation on the bottle-shaped beam after filtering out the out-of-band noise to demodulate the transmission signal.
[0090] In the description of the present application, it should be noted that the orientation or positional relationship indicated by terms such as "upper" and "lower" is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application 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 should not be construed as a limitation to the present application. Unless otherwise clearly specified and defined, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.
[0091] It should be noted that in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the process, method, article or device comprising said element.
[0092] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. An optical wireless obstacle avoidance communication system, characterized in that: The optical wireless obstacle avoidance communication system comprises: A coherent optical transmitter, which is used to coherently modulate the transmission signal into optical carriers of multiple wavelengths, combine the modulated multiple optical signals into one beam, and output linearly polarized light after polarizing the combined optical signal; an obstacle avoidance system for converting the linearly polarized light into circularly polarized light and performing phase reconstruction based on Airy ring Fourier transform to generate a bottle beam; A coherent receiving end is used to couple the bottle beam into an optical fiber for coherent demodulation to demodulate the transmission signal.
2. The optical wireless obstacle avoidance communication system according to claim 1, characterized in that: The obstacle avoidance system comprises: A quarter wave plate, which is used to convert the linearly polarized light into left-handed circularly polarized light or right-handed circularly polarized light; A metasurface that performs phase reconstruction on the left-handed circularly polarized light or the right-handed circularly polarized light based on Airy ring Fourier transform; A first lens is used to make the phase-reconstructed light beam generate a bottle-shaped beam at a focal plane.
3. The optical wireless obstacle avoidance communication system according to claim 2, characterized in that: The obstacle avoidance system also includes: The second lens is used to focus the propagated bottle beam.
4. The optical wireless obstacle avoidance communication system according to claim 2, characterized in that: The metasurface is a geometric phase liquid crystal metasurface, and the micro-nano unit of the geometric phase liquid crystal metasurface includes silicon substrates distributed on both sides, and an orientation film and a liquid crystal layer located between the two silicon substrates.
5. The optical wireless obstacle avoidance communication system according to claim 2, characterized in that: The phase distribution of the metasurface is the phase distribution after the Fourier transform of the Airy ring, wherein the complex amplitude expression of the Airy ring is: Among them, Ai is the Airy function, r0(θ) is the polar coordinate expression of the ring shape, r is the polar distance, θ is the polar angle, w is the scale factor, and a is the attenuation factor.
6. The optical wireless obstacle avoidance communication system according to claim 1, characterized in that: The coherent light transmitting end comprises: A tunable laser for outputting laser light of multiple wavelengths as an optical carrier; A plurality of first polarization controllers, the number of which corresponds to the number of wavelengths, for adjusting the polarization state of each laser beam to be the same; A plurality of modulators, the number of which corresponds to the number of wavelengths, for modulating the transmission signal onto an optical carrier; A wavelength division multiplexer, which is used to combine multiple modulated optical signals into one beam; The second polarization controller is used to output linearly polarized light after polarizing the combined optical signal.
7. The optical wireless obstacle avoidance communication system according to claim 6, characterized in that: The tunable laser is an infrared band tunable laser, which is used to output lasers with four wavelengths in the infrared band.
8. The optical wireless obstacle avoidance communication system according to claim 6, characterized in that: The coherent light transmitting end also includes: A first collimator is used for collimating the output linearly polarized light output by the second polarization controller.
9. The optical wireless obstacle avoidance communication system according to claim 1, characterized in that: The coherent receiving end comprises: a second collimator, for coupling the bottle beam into an optical fiber; an amplifier for amplifying the power of the bottle beam coupled into the optical fiber; A filter for filtering out-of-band noise of the amplified bottle beam; The coherent demodulation device is used to perform coherent demodulation on the bottle beam after filtering out-of-band noise, so as to demodulate the transmission signal.
10. An optical wireless obstacle avoidance communication method using the optical wireless obstacle avoidance communication system according to claim 1, characterized in that: The optical wireless obstacle avoidance communication method comprises: At the coherent optical transmitting end, the transmission signal is coherently modulated into optical carriers of multiple wavelengths, and the modulated multiple optical signals are combined into one beam, and the combined optical signal is polarized and output as linearly polarized light; The linearly polarized light is converted into circularly polarized light by using an obstacle avoidance system, and phase reconstruction is performed based on the Airy ring Fourier transform to generate a bottle beam; At the coherent receiving end, the bottle beam is coupled into the optical fiber for coherent demodulation to demodulate the transmission signal.