A wavelength-division multiplexing multi-user optical wireless communication system based on a spatial light modulator

Abstract

The present invention discloses a wavelength-division multiplexing multi-user optical wireless communication system based on a spatial light modulator. Multi-wavelength signals from a transmitting end enter free space through a multimode optical fiber and a collimating lens, and after being expanded by an achromatic lens system, are irradiated on the spatial light modulator. After being modulated by the multi-wavelength hologram displayed on the spatial light modulator, optical signals of different wavelengths are split and deflected, and focused on corresponding receivers, realizing multi-channel signal transmission. The present invention solves the problem in traditional free-space optical communication that only point-to-point fixed transmission is supported, and multi-user and mobile users are not supported. Operations such as switching between users and multi-user power allocation can be performed, and it has the advantages of strong flexibility and easy deployment, and has good application prospects in free-space optical wireless communication systems.

Description

Technical Field

[0001] The present invention relates to free-space optical communication technology, and particularly to a wavelength-division multiplexing multi-user optical wireless communication system based on a spatial light modulator. Background Art

[0002] With the increasing demand for spectrum resources, optical communication has become an indispensable part of future communication systems. Compared with traditional fiber-optic communication, free-space optical communication technology uses light waves as carriers to transmit wireless laser signals in free space, and has the advantages of strong confidentiality, flexible installation and erection, and high communication rate. At present, the research on free-space laser communication systems between point-to-point has been relatively mature. However, free-space optical communication has many defects. For example, traditional free-space optical communication only supports point-to-point communication, and it is difficult to meet the requirements for multi-user access and user mobility.

[0003] A spatial light modulator is a programmable passive optical device that can be used to adjust the phase of a light beam to achieve beam splitting and deflection. In a free-space optical communication system, a spatial light modulator can be used to achieve multi-user access. However, for multi-user mobile access achieved only by beam splitting through a spatial light modulator, all light beams contain the same information, and it is impossible to distinguish the information between users, and only one-to-many broadcasting can be achieved. Wavelength-division multiplexing technology effectively increases the capacity and bandwidth of the system by multiplexing signals of different wavelengths, and can be used to solve the problem of distinguishing user information. At present, wavelength-division multiplexing technology has been widely applied to traditional fiber-optic communication. However, traditional wavelength demultiplexing devices are more suitable for chip integration, not suitable for the wireless access scenario of mobile users, and have low light energy utilization rate compared with multi-wavelength holograms, which increases the demand for transmission power to a certain extent.

[0004] Therefore, the present invention combines the advantages of both and proposes a wavelength-division multiplexing multi-user optical wireless communication system based on a spatial light modulator. This solution has the advantages of strong flexibility and easy deployment, and has good application prospects in free-space wireless optical communication systems. Summary of the Invention

[0005] Technical Problem: The purpose of the present invention is to provide a wavelength-division multiplexing multi-user optical wireless communication system based on a spatial light modulator, which solves the problem that traditional free-space optical communication only supports point-to-point communication and is difficult to meet multi-user access and user mobility. It realizes free-space laser transmission for multiple mobile users and has a very high light energy utilization rate. The present invention can be used to perform operations such as handover between users and multi-user power allocation, and has the advantages of strong flexibility and easy deployment.

[0006] Technical Solution: A wavelength-division multiplexing multi-user optical wireless communication system based on a spatial light modulator of the present invention mainly includes a transmitting end and a receiving end,

[0007] The transmitting end includes: a laser, a signal source, a multimode optical fiber, and a collimating lens; wherein, the output end of the signal source is connected to the input end of the laser, and the output end of the laser is connected to the collimating lens through the multimode optical fiber; the digital signal output by the signal source is loaded and modulated onto the optical signal by the laser, and then is emitted into free space through the multimode optical fiber and the collimating lens;

[0008] The receiving end includes: a beam expanding system, a spatial light modulator, and a receiving module computer; the spatial light modulator is connected to the computer, and the computer generates a multi-wavelength hologram according to the position of the receiving module and the wavelength of the carrier signal, and transmits it to the spatial light modulator; the signal emitted by the transmitting end is expanded by the beam expanding system and then irradiated on the spatial light modulator. After being modulated by the multi-wavelength hologram displayed on the spatial light modulator, the optical signals of different wavelengths are split and deflected, and focused on the corresponding receiving modules.

[0009] The laser is a multi-wavelength combined laser with digital modulation function.

[0010] The operating wavelength range of the multimode optical fiber includes all designed wavelengths.

[0011] The collimating lens is an achromatic doublet collimating lens coated with an anti-reflection film for the designed wavelength band.

[0012] The beam expanding system is a beam expanding system composed of two achromatic lenses coated with an anti-reflection film for the designed wavelength band and having coincident focal planes, or a commercial achromatic zoom beam expander for the designed wavelength.

[0013] The spatial light modulator is a reflective pure-phase liquid crystal spatial light modulator with a dynamic range greater than 2π in the designed wavelength band.

[0014] The receiving module selects a photodiode with a corresponding wavelength, or various commercial free-space photodetectors.

[0015] The receiving end includes more than two different receiving modules, and each receiving module receives optical signals of different wavelengths.

[0016] The computer generates a multi-wavelength hologram according to the position of the receiving module and the wavelength of the carrier signal, and transmits it to the spatial light modulator.

[0017] Advantageous effects: Compared with the prior art, the present invention adopts the above technical solutions and has the following technical effects.

[0018] 1. The present invention uses a spatial light modulator as the core device for demultiplexing in a free-space optical communication system. Through the multi-wavelength hologram displayed on the spatial light modulator, the deflection and splitting of light beams of different wavelengths are realized, enabling free-space laser transmission to multiple mobile users, and having a very high light energy utilization rate.

[0019] 2. The multi - wavelength hologram can be flexibly adjusted according to parameters such as the position of the receiving module, the number of users, and the user power distribution scheme. Therefore, the present invention can be used to perform operations such as handover between users and multi - user power distribution, and has the advantages of strong flexibility and easy deployment. Brief Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of a wavelength - division multiplexing multi - user optical wireless communication system based on a spatial light modulator according to the present invention.

[0021] Description of the reference numerals: 1 - laser; 2 - signal source; 3 - multimode optical fiber; 4 - collimating lens; 5 - beam expanding system; 6 - spatial light modulator; 7 - receiving module; 8 - computer. Detailed Embodiment

[0022] The present invention will be further described below in conjunction with the drawings and embodiments.

[0023] The present invention includes a transmitting end and a receiving end.

[0024] The transmitting end includes: a laser, a signal source, a multimode optical fiber, and a collimating lens; wherein, the output end of the signal source is connected to the input end of the laser, and the output end of the laser is connected to the collimating lens through the multimode optical fiber; the digital signal output by the signal source is loaded and modulated onto the optical signal by the laser, and then exits into the free space through the multimode optical fiber and the collimating lens.

[0025] The receiving end includes: a beam expanding system, a spatial light modulator, a receiving module, and a computer. The spatial light modulator is connected to the computer. The computer generates a multi - wavelength hologram according to the position of the receiving module and the carrier signal wavelength, and transmits it to the spatial light modulator. The signal emitted from the transmitting end is expanded by the beam expanding system and then irradiated on the spatial light modulator. After being modulated by the multi - wavelength hologram displayed on the spatial light modulator, the optical signals of different wavelengths are split and deflected, and focused on the corresponding receiving modules.

[0026] The receiving end includes two or more different receiving modules, and each receiving module is mainly composed of an electro - optical modulator for receiving optical signals of different wavelengths.

[0027] As Figure 1 shown, the wavelength - division multiplexing multi - user optical wireless communication system based on a spatial light modulator mainly includes a transmitting end and a receiving end.

[0028] The transmitting end includes:

[0029] Laser 1, Oxxius L4Cc multi - wavelength combined laser

[0030] The signal source 2 uses a 50 Mb / s pseudo-random binary sequence modulated by TTL to simulate the modulated signal in actual applications.

[0031] The multimode optical fiber 3 is an FG105LVA multimode optical fiber.

[0032] The collimating lens 4 is an F810FC-405 air-gap doublet collimator.

[0033] The output end of the signal source 2 is connected to the input end of the laser 1, and the output end of the laser 1 is connected to the collimating lens 4 through the multimode optical fiber 3. For a free-space optical communication system with 3 users, the pseudo-random binary sequence output by the signal source 2 is loaded by the laser 1 onto optical carriers with wavelengths of 405 nm, 488 nm, and 560 nm respectively, and then exits into free space via the multimode optical fiber 3 and the collimating lens 4.

[0034] The receiving end includes:

[0035] The beam expander system 5 is a ZBE2A achromatic zoom beam expander.

[0036] The spatial light modulator 6 is an EXULUS-HD1 spatial light modulator.

[0037] The receiving module 7 is a DET025A free-space detector.

[0038] The computer 8 includes various commercial computers installed with the control program of the spatial light modulator 6.

[0039] The receiving end contains two or more different receiving modules 7, and each receiving module 7 receives optical signals of different wavelengths. The spatial light modulator 6 is connected to the computer 8. The computer 8 generates a multi-wavelength hologram according to the positions of the receiving modules 7 and the wavelengths of the 3 optical signals, and transmits it to the spatial light modulator 6. The signal emitted by the transmitting end is expanded by the beam expander system 5 and then irradiated on the spatial light modulator 6. After being modulated by the multi-wavelength hologram displayed on the spatial light modulator, the optical signals of different wavelengths are split and deflected, and focused on the corresponding receiving modules 7.

[0040] The present invention uses a spatial light modulator as the core device for demultiplexing in a free-space optical communication system. Through the multi-wavelength hologram displayed on the spatial light modulator, the deflection and splitting of light beams of different wavelengths are realized, achieving free-space laser transmission to multiple mobile users with high light energy utilization rate. The multi-wavelength hologram can be flexibly adjusted according to parameters such as the positions of the receiving modules, the number of users, and the user power distribution scheme. Therefore, the present invention can be used to perform operations such as switching between users and multi-user power distribution, and has the advantages of strong flexibility and easy deployment, and has good application prospects in free-space wireless optical communication systems.

Claims

1. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator, characterized in that: It mainly includes a transmitting end and a receiving end. The transmitting end includes: a laser (1), a signal source (2), a multimode optical fiber (3), and a collimating lens (4); among them, the output end of the signal source (2) is connected to the input end of the laser (1), and the output end of the laser (1) is connected to the collimating lens (4) through the multimode optical fiber (3); the digital signal output by the signal source (2) is loaded and modulated onto the optical signal by the laser (1), and then exits into free space through the multimode optical fiber (3) and the collimating lens (4). The receiving end includes: a beam expansion system (5), a spatial light modulator (6), a receiving module (7), and a computer (8); the spatial light modulator (6) is connected to the computer (8), and the computer (8) generates a multi-wavelength hologram according to the position of the receiving module (7) and the wavelength of the carrier signal, and transmits it to the spatial light modulator (6); the signal emitted from the transmitting end is expanded by the beam expansion system (5) and then irradiated on the spatial light modulator (6). After being modulated by the multi-wavelength hologram displayed on the spatial light modulator, the optical signals of different wavelengths are split and deflected and focused on the corresponding receiving module (7). The receiving end contains more than two different receiving modules (7), and each receiving module (7) receives optical signals of different wavelengths.

2. The wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, characterized in that, The laser (1) is a multi-wavelength combined laser with digital modulation function.

3. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, wherein The working wavelength range of the multimode optical fiber (3) includes all designed wavelengths.

4. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, characterized in that, The collimating lens (4) is an achromatic doublet collimating lens coated with an antireflection film for the designed wavelength band.

5. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, wherein The beam expansion system (5) is a beam expansion system composed of two achromatic lenses coated with antireflection films for the designed wavelength band with their focal planes coinciding, or a commercial achromatic zoom beam expander for the designed wavelength.

6. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, characterized in that, The spatial light modulator (6) is a reflective pure-phase liquid crystal spatial light modulator with a dynamic range greater than 2π in the designed wavelength band.

7. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, characterized in that, The receiving module (7) selects a photodiode with the corresponding wavelength, or various commercial free-space photodetectors.

8. A wavelength division multiplexing multi-user optical wireless communication system based on a spatial light modulator according to claim 1, characterized in that, The computer (8) generates a multi-wavelength hologram according to the position of the receiving module (7) and the wavelength of the carrier signal, and transmits it to the spatial light modulator (6).

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