An underwater full-duplex LED optical imaging MIMO real-time communication system and method

Abstract

The present invention discloses an underwater full-duplex LED optical imaging MIMO real-time communication system and method. Its imaging underwater visible light communication system can use an imaging lens to separate the received optical signal into multiple light spots, so as to reduce the interference between optical signals of different links, simplify the complexity of the signal processing equipment at the receiving end, reduce the multi-access interference and alignment requirements, and thus the original signal can be independently recovered without using an additional MIMO demodulation algorithm. In addition, an optical receiving system using an optical fiber array to couple and conduct the optical signal to a photodetector is adopted, so that the photodetector array can be arbitrarily arranged anywhere in the communication housing, and does not necessarily need to be located directly behind the imaging lens. Thus, on the basis of effectively separating the light spots, the size of the communication machine is effectively reduced, making the communication machine easier to move and deploy. The present invention can realize the separation reception and detection of imaging light spots with a small distance without increasing the complexity of the optical system at the receiving end.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly relates to an underwater full-duplex LED optical imaging MIMO real-time communication system and method. Background Art

[0002] China has a vast ocean area. Activities such as maritime disaster warning, coastal vigilance, resource exploration, and pollution monitoring all require using communication technologies to transmit underwater data to the water surface in real time or near real time, and then forward it to shore-based or satellite. However, currently, underwater acoustic communication suitable for long-distance underwater communication has a narrow bandwidth, while underwater radio frequency communication has a large propagation attenuation problem. Considering that seawater has relatively small attenuation for blue-green light with a wavelength of 450 nm to 550 nm, the underwater wireless optical communication technology based on the blue-green light band can be used as a powerful supplement to underwater communication. For this reason, a non-imaging MIMO underwater wireless visible light communication system was proposed in the master's thesis "Research on Key Technologies of Underwater Visible Light Non-imaging MIMO" by Su Haoming of Guilin University of Electronic Technology and the master's thesis "Underwater Wireless Visible Light Communication System Based on MIMO-OFDM" by Song Yuhang of Zhejiang University. However, during the underwater optical transmission of multiple visible light signals emitted by the transmitting end of the system, due to the influence of water quality absorption, scattering, turbulence, and transceiver misalignment, etc., when the receiving end of the system uses multiple independent photodetectors to receive these visible light signals, it will inevitably make the subsequent detection of multiple visible light signals extremely difficult. Therefore, it is necessary to design complex signal detection algorithms to achieve the detection of asymmetrically distributed multiple visible light signals, but it is powerless for the detection of symmetrically distributed multiple visible light signals. Summary of the Invention

[0003] Aiming at the problems of difficult and complex detection of multiple visible light signals in the existing non-imaging MIMO underwater wireless visible light communication system, the present invention provides an underwater full-duplex LED optical imaging MIMO real-time communication system and method.

[0004] To solve the above problems, the present invention is realized through the following technical solutions:

[0005] An underwater full-duplex LED optical imaging MIMO real-time communication system includes 2 communication terminals with coincident main axes; each communication terminal consists of a communicator located underwater and a host computer located above water; each communicator includes a hermetically sealed and waterproof communication housing, and an LED visible light source array, a collimating lens array, an imaging lens, a coupled optical fiber array, a photodetector array, a transmitting electrical module, and a receiving electrical module arranged inside the communication housing. The output end of the host computer is electrically connected to the input end of the transmitting electrical module of the communicator, and the output end of the transmitting electrical module is electrically connected to the LED visible light source array; the LED visible light source array consists of 2N LED visible light sources, and these 2N LED visible light sources are fixed on a light source bracket and are arranged in central symmetry with the main axis of the communicator as the center; the collimating lens array consists of 2N collimating lenses, and these 2N collimating lenses are fixed on the edge of the front end face of the communication housing and are arranged in central symmetry with the main axis of the communicator as the center; the light source bracket is located directly behind the front end face of the communication housing; the arrangement shape of the collimating lens array on the front end face of the communication housing is exactly the same as the arrangement shape of the LED visible light source array on the light source mounting plane of the light source bracket; one collimating lens of the collimating lens array corresponds to one LED visible light source of the LED visible light source array respectively, and the main optical axis of the collimating lens coincides with the main optical axis of its corresponding LED visible light source. The imaging lens is fixed at the center of the front end face of the communication housing, and the main optical axis of the imaging lens coincides with the main axis of the communicator; an imaging filter is provided on the front end face of the imaging lens; the coupled optical fiber array consists of 2N coupled optical fibers, and these 2N coupled optical fibers are fixed on an optical fiber bracket and are arranged in central symmetry with the main axis of the communicator as the center; the optical fiber bracket is located directly behind the front end face of the communication housing; the arrangement shape of the coupled optical fiber array on the optical fiber mounting plane of the optical fiber bracket is exactly the same as the arrangement shape of the collimating lens array on the front end face of the communication housing; one coupled optical fiber of the coupled optical fiber array corresponds to one collimating lens of the collimating lens array respectively, and the main optical axis of the coupled optical fiber is parallel to the main optical axis of its corresponding collimating lens; the incident surfaces of all the coupled optical fibers are located on the focal plane of the imaging lens, and the 2N imaging spots formed by the imaging lens respectively fall on the incident surfaces of the 2N coupled optical fibers; the photodetector array consists of 2N photodetectors, and the input ends of these 2N photodetectors are respectively connected to the output surfaces of the 2N coupled optical fibers; the output end of the photodetector array is electrically connected to the input end of the receiving electrical module, and the output end of the receiving electrical module is electrically connected to the input end of the host computer. The above N is a positive integer greater than or equal to 1.

[0006] In the above solution, the distances between the main optical axes of the 2N LED visible light sources and the main axis of the communicator are equal, the distances between the main optical axes of the 2N collimating lenses and the main axis of the communicator are equal, and the distances between the main optical axes of the 2N coupled optical fibers and the main axis of the communicator.

[0007] In the above solution, the distance between the main optical axis of the LED visible light source and the main axis of the communication machine is equal to the distance between the main optical axis of the collimating lens and the main axis of the communication machine, and both the distance between the main optical axis of the LED visible light source and the main axis of the communication machine and the distance between the main optical axis of the collimating lens and the main axis of the communication machine are greater than the distance between the main optical axis of each coupling optical fiber and the main axis of the communication machine.

[0008] In the above solution, the distance r between the main optical axis of the coupling optical fiber and the main axis of the communication machine is:

[0009]

[0010] In the formula, R is the distance between the main optical axis of the LED visible light source and the main axis of the communication machine, that is, the distance between the main optical axis of the collimating lens and the main axis of the communication machine; L is the distance between the front end faces of the two communication ends, that is, the communication distance; F is the focal length of the imaging lens.

[0011] In the above solution, the radius r of the coupling optical fiber 光纤 has a value range of:

[0012]

[0013] In the formula, r is the distance between the main optical axis of the coupling optical fiber and the main axis of the communication machine; D is the diameter of the imaging lens; F is the focal length of the imaging lens.

[0014] In the above solution, the central wavelengths of the 2N LED visible light sources of the same communication end are the same, while the central wavelengths of the 2N LED visible light sources of the LED visible light source arrays of the two communication ends are different.

[0015] In the above solution, the imaging filter at the center of the communication front end face has the same central wavelength as the LED visible light source array of the other communication end.

[0016] In the above solution, the front end face of the communication housing, the light source mounting plane of the light source bracket, and the optical fiber mounting plane of the optical fiber bracket are parallel to each other and are all perpendicular to the main axis of the communication machine.

[0017] An underwater full-duplex LED optical imaging MIMO real-time communication method includes the following steps:

[0018] Step 1, at the communication end serving as the sending end, the upper computer sends the source signal to the transmitting electrical module of the communication machine, and the transmitting electrical module performs baseband signal processing and LED driving on the source signal and then sends it into the LED visible light source array;

[0019] Step 2, the 2N LED visible light sources of the LED visible light source array emit 2N paths of visible light under the drive of the transmitted signal, and these 2N paths of visible light are simultaneously emitted into the underwater channel through the 2N collimating lenses of the collimating lens array;

[0020] Step 3: At the communication terminal acting as the receiving end, the imaging lens of the communication machine separates the visible light received through the underwater channel and forms 2N light spots. These 2N light spots respectively fall on the incident surfaces of 2N coupling optical fibers of the coupling optical fiber array to form 2N paths of visible light; the 2N coupling optical fibers of the coupling optical fiber array send the 2N paths of visible light to 2N photodetectors of the photodetector array; the 2N photodetectors of the photodetector array perform photoelectric conversion on the 2N paths of visible light and then send them to the receiving electrical module.

[0021] Step 4: The receiving electrical module amplifies, performs zero-forcing detection, and processes the baseband signal on the 2N paths of visible light after photoelectric conversion, and then sends it to the upper computer, and the upper computer restores it to the source signal.

[0022] The baseband signal process of the transmitting electrical module is successively RS coding, inserting frame synchronization and bit synchronization codes, 8B / 10B coding, and serial-to-parallel conversion; the baseband signal process of the receiving electrical module is successively parallel-to-serial conversion, 8B / 10B decoding, judging frame synchronization and bit synchronization codes, and RS decoding.

[0023] Compared with the prior art, the present invention has the following characteristics:

[0024] 1. Compared with the traditional non-imaging underwater wireless visible light communication system, the imaging underwater wireless visible light communication system of the present invention can use the imaging lens to separate the received optical signal to form multiple light spots, so as to reduce the interference between optical signals of different links, simplify the complexity of the signal processing related equipment at the receiving end, can separate optical signals in different incident directions, reduce multiple access interference and alignment requirements, and thus can independently recover the original signal without using an additional MIMO demodulation algorithm.

[0025] 2. Considering that the size distribution of the imaging light spot formed by the imaging lens will change with the change of the communication distance. When the communication distance is long, the optical signal received at the receiving end is approximately parallel light, which will make the spot spacing of the image formed by a single imaging lens small. The diameter of the photosensitive surface of a common photodetector is about a few millimeters. Therefore, when the distribution range of the imaging light spots at the receiving end is much smaller than the detection target surface of the entire photodetector array, the imaging light spots cannot be directly detected and received by the corresponding APD detector array at the receiving end. Although the spot spacing of the images in different optical paths can be enlarged by adding a concave lens or other lenses behind the imaging lens at the receiving end, adding a concave lens to enlarge the spot spacing of the imaging light spots will introduce aberration, resulting in an increase in the complexity of the optical system at the receiving end. Since the diameter of the optical fiber is much smaller than the size of the photodetector, therefore, in the present invention, a coupling optical fiber array is added between the imaging lens and the photodetector array, and the optical fiber array is used to couple and conduct the optical signal to the optical receiving system of the photodetector. In this way, the photodetector array can be arbitrarily arranged anywhere in the communication housing, and does not necessarily need to be located directly behind the imaging lens, thereby effectively reducing the size of the communication machine on the basis of effectively separating the light spots, making the communication machine easier to move and deploy;

[0026] 3. The present invention can realize the separation, reception and detection of imaging light spots with small spacing without increasing the complexity of the optical system at the receiving end. Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of an underwater full-duplex LED optical imaging MIMO real-time communication system.

[0028] Figure 2 It is a principle block diagram of the transmitting electrical module and the receiving electrical module of the communication machine.

[0029] Figure 3 It is a measured bit error rate performance curve of an underwater full-duplex LED optical imaging MIMO real-time communication system.

[0030] Reference numerals in the figure: 1. LED visible light source array; 2. Collimating lens array; 3. Imaging lens; 4. Coupling optical fiber array; 5. Photodetector array; 6. Filter. Detailed Embodiments

[0031] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to specific examples.

[0032] An underwater full-duplex LED optical imaging MIMO real-time communication system, as Figure 1As shown, it includes two communication terminals. Each communication terminal consists of a communicator located underwater and a host computer located above water. Each communicator includes a sealed and waterproof communication housing, and an LED visible light source array 1, a collimating lens array 2, an imaging lens 3, a coupled optical fiber array 4, a photodetector array 5, a transmitting electrical module, and a receiving electrical module arranged inside the communication housing. N is a positive integer greater than or equal to 1.

[0033] The two communication terminals can both be divided into three parts: a host computer, a transmitting part, and a receiving part. The transmitting part includes the LED visible light source array 1, the collimating lens array 2, and the transmitting electrical module. The receiving part includes the imaging lens 3, the coupled optical fiber array 4, the photodetector array 5, and the receiving electrical module. In this way, when full-duplex communication is carried out between the two communication terminals, the transmitting part of communication terminal A communicates with the receiving part of communication terminal B, and the transmitting part of communication terminal B communicates with the receiving part of communication terminal A.

[0034] 1.1) Transmitting electrical module

[0035] The transmitting electrical module includes a transmitting signal processing unit and an LED driving unit. The input end of the transmitting signal processing unit forms the input end of the transmitting electrical module. The output end of the transmitting signal processing unit is connected to the input end of the LED driving unit. The output end of the LED driving unit forms the output end of the transmitting electrical module. The output end of the host computer is electrically connected to the input end of the transmitting electrical module of the communicator. The output end of the transmitting electrical module is electrically connected to the LED visible light source array 1. In this embodiment, the transmitting signal processing unit is composed of an FPGA signal processing board card, which is used to complete baseband signal processing. It obtains the host computer source signal through an Ethernet port, and performs RS coding, inserts frame synchronization and bit synchronization codes, 8B / 10B coding, and serial-to-parallel conversion on the source signal, and then sends it to the LED driving unit. As Figure 2 shown.

[0036] 1.2) Transmitting optical module

[0037] The LED visible light source array 1 consists of 2N LED visible light sources. These 2N LED visible light sources are fixed on a light source bracket directly behind the front end face of the communication housing, and are arranged in central symmetry with the main axis of the communicator as the center. The main optical axes of the 2N LED visible light sources are at equal distances from the main axis of the communicator, and are all R. In this embodiment, the LED visible light source array 1 consists of 4 LED visible light sources, and these 4 LED visible light sources are respectively located at the four corners of the light source bracket. The light source mounting plane of the light source bracket and the front end face of the communication housing are parallel to each other, and are both perpendicular to the main axis of the communicator.

[0038] The collimating lens array 2 is composed of 2N collimating lenses. These 2N collimating lenses are fixed on the edge of the front end face of the communication housing and are arranged in central symmetry with the main axis of the communication machine as the center. The distances from the principal optical axes of the 2N collimating lenses to the main axis of the communication machine are equal, all being R. In this embodiment, the collimating lens array 2 consists of 4 collimating lenses, and these 4 collimating lenses are respectively located at the four corners of the front end face of the communication housing. The collimating lens is used to reduce the beam divergence angle.

[0039] The arrangement shape of the collimating lens array 2 on the front end face of the communication housing is exactly the same as the arrangement shape of the LED visible light source array 1 on the light source mounting plane of the light source bracket. One collimating lens of the collimating lens array 2 corresponds to one LED visible light source of the LED visible light source array 1, and the principal optical axis of the collimating lens coincides with the principal optical axis of its corresponding LED visible light source.

[0040] 2.1) Receiving optical module

[0041] The imaging lens 3 is fixed at the center of the front end face of the communication housing, and the principal optical axis of the imaging lens 3 coincides with the main axis of the communication machine. In order to filter out the interference of visible light in the channel environment, a filter 6 is provided on the front end face of the imaging lens 3. The imaging lens 3 separates the approximately parallel incident visible light to obtain 2N optical signals, and 2N corresponding light spots will be imaged at the focal plane. In this embodiment, the imaging lens 3 uses a plano-convex lens GCL-010123, with its aperture D being 76 mm and its focal length F being 300 mm.

[0042] The coupling fiber array 4 is composed of 2N coupling fibers. These 2N coupling fibers are fixed on the fiber bracket directly behind the front end face of the communication housing and are arranged in central symmetry with the main axis of the communication machine as the center. The distances from the principal optical axes of the 2N coupling fibers to the main axis of the communication machine are equal, all being r. In this embodiment, the coupling fiber array 4 consists of 4 coupling fibers, and these 4 coupling fibers are respectively located at the four corners of the fiber bracket. The fiber mounting plane of the fiber bracket and the front end face of the communication housing are parallel to each other and are both perpendicular to the main axis of the communication machine.

[0043] The arrangement shape of the coupling fiber array 4 on the fiber mounting plane of the fiber bracket is exactly the same as the arrangement shape of the collimating lens array 2 on the front end face of the communication housing. One coupling fiber of the coupling fiber array 4 corresponds to one collimating lens of the collimating lens array 2, and the principal optical axis of the coupling fiber is parallel to the principal optical axis of its corresponding collimating lens. The incident surfaces of all coupling fibers are located on the focal plane of the imaging lens 3, and the imaging light spots formed by the imaging lens 3 fall on the incident surfaces of the coupling fibers corresponding to them.

[0044] In order to reduce the interference between each optical path, the present invention uses an imaging lens 3 to separate the transmitted optical signals and form multiple light spots. However, if a photodetector array 5 is directly used to receive the light spots separated by the imaging lens 3, limited by the size of the photodetector, when the distribution range of the imaging light spots formed by the imaging lens 3 is much smaller than the detection target surface of the entire photodetector array 5, the imaging light spots cannot be directly detected and received by the photodetector array 5. Therefore, the present invention designs a coupling optical fiber array 4 with a small aperture between the imaging lens 3 and the photodetector array 5 to receive and conduct the light spot signals. When selecting the core diameter of the coupling optical fiber used in the coupling optical fiber array 4, the radius r of each coupling optical fiber 光纤 should be within the range of When considering the arrangement of the coupling optical fiber array 4 on the focal plane, according to the principle of geometric optics, the distance r between the main optical axis of the coupling optical fiber and the main axis of the communication machine is related to the distance R between the main optical axis of the LED visible light source and the main axis of the communication machine, the communication distance L, and the focal length F of the imaging lens 3, and This can ensure that the imaging light spots formed by the imaging lens 3 can be coupled to each coupling optical fiber of the coupling optical fiber array 4. Where r is the distance between the main optical axis of the coupling optical fiber and the main axis of the communication machine; R is the distance between the main optical axis of the LED visible light source and the main axis of the communication machine, that is, the distance between the main optical axis of the collimating lens and the main axis of the communication machine; D is the diameter of the imaging lens 3; F is the focal length of the imaging lens 3; L is the distance between the front end faces of the two communication ends, that is, the communication distance. Since the coupling optical fiber has a short distance and low loss, the back end of the coupling optical fiber is closely adjacent to the photodetector for photoelectric conversion, and can effectively conduct the optical signal to the photodetector.

[0045] The photodetector array 5 is composed of 2N photodetectors. One photodetector of the photodetector array 5 corresponds to one coupling optical fiber of the coupling optical fiber array 4, and the incident end of the photodetector is coupled to the output end face of its corresponding coupling optical fiber. In this embodiment, the photodetector array 5 is composed of 4 photodetectors, and these 4 photodetectors can be fixed in any gap of the communication housing, thereby reducing the size of the communication machine.

[0046] The above receiving optical part can effectively separate and detect the imaging light spots of different optical paths, thereby providing a key method basis for the MIMO communication system based on spatial multiplexing and improving the multiplexing gain of the MIMO communication system.

[0047] 2.2) Receiving electrical module

[0048] The receiving electrical module includes a signal amplification unit and a received signal processing unit. The input end of the signal amplification unit forms the input end of the receiving electrical module. The output end of the signal amplification unit is connected to the input end of the received signal processing unit, and the output end of the received signal processing unit forms the output end of the receiving electrical module. The output end of the photodetector array 5 is electrically connected to the input end of the receiving electrical module, and the output end of the receiving electrical module is electrically connected to the input end of the host computer. In this embodiment, the received signal processing unit is composed of an FPGA signal processing board, which is used to complete MIMO detection and baseband signal processing. It detects the amplified signal sent by the received signal amplification unit through the MIMO detection algorithm, and performs parallel-to-serial conversion, 8B / 10B decoding, determination of frame synchronization and bit synchronization codes, and RS decoding on the detected signal to recover the source signal, and finally returns it to the host computer at the receiving end through Ethernet. As Figure 2 shown.

[0049] When two communication terminals are performing real-time duplex communication, the LED visible light source arrays 1 of the two communication terminals respectively adopt LED visible light source arrays 1 with different central wavelengths, while the central wavelengths of the 2N LED visible light sources of the LED visible light source array 1 of the same communication terminal are the same. For example, in this embodiment, the central wavelengths of the LED visible light source arrays 1 of the two communication terminals are 450 nm (blue light) and 530 nm (green light) respectively. The LED visible light source with a central wavelength of 450 nm selects the lamp bead of LXR0-SR00. The supply voltage of this lamp bead is 12V and the working current is 700 mA. The LED visible light source with a central wavelength of 530 nm selects the Epistar lamp bead. The supply voltage of this lamp bead is 7V and the working current is 700 mA. The measured divergence angle of the green light beam is 3.54°, and the measured divergence angle of the blue light beam is 3.86°. In addition, the imaging filter 6 has the same central wavelength as the LED visible light source array 1 of the other communication terminal to avoid the interference of the backward scattered light beam and background light between the transceiver and the light source itself. In this embodiment, the two communication terminals both adopt the filter 6 that filters the blue and green light wavelengths.

[0050] An underwater full-duplex LED optical imaging MIMO real-time communication method implemented by the above system includes the following steps:

[0051] Step 1, at the communication terminal acting as the transmitting end, the host computer sends the source signal to the transmitting electrical module of the communicator. The transmitting electrical module performs baseband signal processing and LED driving on the source signal and then sends it to the LED visible light source array 1; among them, the baseband signal process is RS encoding, inserting frame synchronization and bit synchronization codes, 8B / 10B encoding, and serial-to-parallel conversion in sequence.

[0052] Step 2: The 2N LED visible light sources of the LED visible light source array 1 emit 2N paths of visible light under the drive of the emission signal, and these 2N paths of visible light are simultaneously emitted into the underwater channel through the 2N collimating lenses of the collimating lens array 2.

[0053] Step 3: At the communication terminal acting as the receiving end, the imaging lens 3 of the communication machine separates the visible light received through the underwater channel and forms 2N light spots, and these 2N light spots respectively fall on the incident surfaces of the 2N coupling optical fibers of the coupling optical fiber array 4 to form 2N paths of visible light; the 2N coupling optical fibers of the coupling optical fiber array 4 send the 2N paths of visible light to the 2N photodetectors of the photodetector array 5; the 2N photodetectors of the photodetector array 5 perform photoelectric conversion on the 2N paths of visible light and then send them to the receiving electrical module.

[0054] Step 4: The receiving electrical module amplifies, performs zero-forcing detection and baseband signal processing on the 2N paths of visible light after photoelectric conversion and then sends them to the upper computer, and the upper computer restores them to the source signal; the baseband signal process is in sequence parallel-to-serial conversion, 8B / 10B decoding, judging frame synchronization and bit synchronization codes, and RS decoding.

[0055] Since the present invention uses the imaging lens 3, the coupling optical fiber array 4 and the photoelectric detection array in the receiving optical part of the communication machine to receive and convert optical signals, and the imaging lens 3 reduces the optical signal interference between sub-channels, so there is no need for a complex MIMO detection algorithm in the receiving electrical part of the communication machine. As long as zero-forcing detection is used, the baseband signal can be directly obtained. In this way, it is possible to realize the separated reception and detection of imaging light spots with a small distance without overly increasing the complexity of the receiving end optical system and simplify the detection algorithm. Figure 3 This is the measured bit error rate performance curve of the present invention. It can be seen from the figure that when the communication distance is 12 - 24 meters, the system bit error rate performance is very good, and the bit error rate is close to 0. When it is less than 12 meters and greater than 24 meters, due to the aliasing of the light spots and the generation of mutual interference, the bit error rate performance decreases.

[0056] It should be noted that although the embodiments described above of the present invention are illustrative, this is not a limitation of the present invention. Therefore, the present invention is not limited to the above specific embodiments. Without departing from the principle of the present invention, any other embodiments obtained by those skilled in the art under the inspiration of the present invention are regarded as within the protection scope of the present invention.

Claims

1. An underwater full-duplex LED optical imaging MIMO real-time communication system, comprising two communication terminals with coincident main axes; characterized in that, Each communication terminal consists of a communicator located underwater and a host computer located above water; Each communicator includes a sealed and waterproof communication housing, and an LED visible light source array (1), a collimating lens array (2), an imaging lens (3), a coupled optical fiber array (4), a photodetector array (5), a transmitting electrical module, and a receiving electrical module disposed inside the communication housing; the LED visible light source array (1), the collimating lens array (2), and the transmitting electrical module form the transmitting part of the communicator, and the imaging lens (3), the coupled optical fiber array (4), the photodetector array (5), and the receiving electrical module form the receiving part of the communicator; The output end of the host computer is electrically connected to the input end of the transmitting electrical module of the communicator, and the output end of the transmitting electrical module is electrically connected to the LED visible light source array (1); the LED visible light source array (1) consists of 2N LED visible light sources, and these 2N LED visible light sources are fixed on the light source bracket and are arranged in a centrosymmetric manner centered on the main axis of the communicator; the collimating lens array (2) consists of 2N collimating lenses, and these 2N collimating lenses are fixed on the edge of the front end face of the communication housing and are arranged in a centrosymmetric manner centered on the main axis of the communicator; the light source bracket is located directly behind the front end face of the communication housing; the arrangement shape of the collimating lens array (2) on the front end face of the communication housing is exactly the same as the arrangement shape of the LED visible light source array (1) on the light source mounting plane of the light source bracket; one collimating lens of the collimating lens array (2) corresponds to one LED visible light source of the LED visible light source array (1), and the main optical axis of the collimating lens coincides with the main optical axis of its corresponding LED visible light source; An imaging filter (6) is provided on the front end face of the imaging lens (3); the imaging lens (3) is fixed at the center of the front end face of the communication housing, and the main optical axis of the imaging lens (3) coincides with the main axis of the communicator; the imaging lens (3) separates the approximately parallel incident visible light into 2N optical signals, and 2N corresponding light spots will be imaged at the focal plane; the coupled optical fiber array (4) consists of 2N coupled optical fibers; The numerical aperture NA of each coupled optical fiber 光纤 satisfies the following conditions: The radius r of each coupled optical fiber 光纤 satisfies the following conditions: In the formula, r is the distance between the main optical axis of the coupled optical fiber and the main axis of the communicator; D is the diameter of the imaging lens (3); F is the focal length of the imaging lens (3); These 2N coupled optical fibers are fixed on the optical fiber bracket and are arranged in a centrosymmetric manner centered on the main axis of the communicator; the distances between the main optical axes of the 2N coupled optical fibers and the main axis of the communicator are equal, and the distance r between the main optical axis of the coupled optical fiber and the main axis of the communicator is: In the formula, R is the distance between the main optical axis of the LED visible light source and the main axis of the communicator, that is, the distance between the main optical axis of the collimating lens and the main axis of the communicator; L is the distance between the front end faces of the two communication terminals, that is, the communication distance; F is the focal length of the imaging lens (3); The optical fiber support is located directly behind the front end face of the communication housing; the arrangement shape of the coupled optical fiber array (4) on the optical fiber mounting plane of the optical fiber support is exactly the same as the arrangement shape of the collimating lens array (2) on the front end face of the communication housing; one coupled optical fiber of the coupled optical fiber array (4) corresponds to one collimating lens of the collimating lens array (2) respectively, and the main optical axis of the coupled optical fiber is parallel to the main optical axis of its corresponding collimating lens; the incident surfaces of all the coupled optical fibers are located on the focal plane of the imaging lens (3), and the 2N imaging spots formed by the imaging lens (3) respectively fall on the incident surfaces of the 2N coupled optical fibers; the photodetector array (5) is composed of 2N photodetectors, and the input ends of the 2N photodetectors are respectively connected to the output surfaces of the 2N coupled optical fibers; the output end of the photodetector array (5) is electrically connected to the input end of the receiving electrical module, and the output end of the receiving electrical module is electrically connected to the input end of the host computer; In the receiving optical part of the communication machine, the imaging lens (3), the coupled optical fiber array (4) and the photodetector array (5) are used for receiving and converting optical signals. The imaging lens (3) separates the received optical signals to form multiple spots to reduce the optical signal interference between sub-channels. Therefore, in the receiving electrical part of the communication machine, there is no need for a complex MIMO detection algorithm. As long as zero-forcing detection is used, the baseband signal can be directly obtained. In this way, it is possible to realize the separation and reception detection of imaging spots with a small distance without excessively increasing the complexity of the receiving optical part and simplify the detection algorithm; The above N is a positive integer greater than or equal to 1.

2. The underwater full-duplex LED optical imaging MIMO real-time communication system according to claim 1, characterized in that, The main optical axes of the 2N LED visible light sources are at equal distances from the main axis of the communication machine, and the main optical axes of the 2N collimating lenses are at equal distances from the main axis of the communication machine.

3. The underwater full-duplex LED optical imaging MIMO real-time communication system according to claim 2, characterized in that, The distance between the main optical axis of the LED visible light source and the main axis of the communication machine is equal to the distance between the main optical axis of the collimating lens and the main axis of the communication machine, and the distance between the main optical axis of the LED visible light source and the main axis of the communication machine and the distance between the main optical axis of the collimating lens and the main axis of the communication machine are both greater than the distance between the main optical axis of each coupled optical fiber and the main axis of the communication machine.

4. An underwater full-duplex LED optical imaging MIMO real-time communication system according to claim 1, characterized in that, The central wavelengths of the 2N LED visible light sources of the same communication end are the same, while the central wavelengths of the 2N LED visible light sources of the LED visible light source array (1) of the two communication ends are different.

5. An underwater full-duplex LED optical imaging MIMO real-time communication system according to claim 4, wherein the imaging filter (6) at the center of the front end face of the communication is the same as the central wavelength of the LED visible light source array (1) of the other communication end.

6. An underwater full-duplex LED optical imaging MIMO real-time communication system according to claim 1, characterized in that, The front end face of the communication housing, the light source mounting plane of the light source support and the optical fiber mounting plane of the optical fiber support are parallel to each other and are all perpendicular to the main axis of the communication machine.

7. A real-time underwater full-duplex LED optical imaging MIMO communication method implemented by the system according to claim 1, characterized in that It includes the following steps: Step 1, at the communication end acting as the transmitting end, the host computer sends the source signal to the transmitting electrical module of the communication machine, and the transmitting electrical module performs baseband signal processing and LED driving on the source signal and then sends it to the LED visible light source array (1); Step 2: The 2N LED visible light sources of the LED visible light source array (1) emit 2N paths of visible light under the drive of the transmitted signal. These 2N paths of visible light are simultaneously transmitted into the underwater channel through the 2N collimating lenses of the collimating lens array (2); Step 3: At the communication terminal acting as the receiving end, the imaging lens (3) of the communication machine separates the visible light received through the underwater channel and forms 2N light spots. These 2N light spots respectively fall on the incident surfaces of the 2N coupling optical fibers of the coupling optical fiber array (4) to form 2N paths of visible light; The 2N coupling optical fibers of the coupling optical fiber array (4) send the 2N paths of visible light to the 2N photodetectors of the photodetector array (5); The 2N photodetectors of the photodetector array (5) perform photoelectric conversion on the 2N paths of visible light and then send them to the receiving electrical module; Step 4: The receiving electrical module amplifies, performs zero-forcing detection, and processes the baseband signal on the 2N paths of visible light after photoelectric conversion, and then sends them to the upper computer. The upper computer restores them to the source signal.

8. An underwater full-duplex LED optical imaging MIMO real-time communication method according to claim 7, characterized in that The baseband signal process of the transmitting electrical module is successively RS coding, inserting frame synchronization and bit synchronization codes, 8B / 10B coding, and serial-to-parallel conversion; The baseband signal process of the receiving electrical module is successively parallel-to-serial conversion, 8B / 10B decoding, judging frame synchronization and bit synchronization codes, and RS decoding.

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