Optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning

Abstract

The application discloses an optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning, and relates to the technical field of optical communication.The method comprises the following steps: converting a binary bit stream corresponding to an image to be transmitted into a plurality of code symbol according to a preset encoding scheme; the preset encoding scheme comprises a one-to-one correspondence relationship between each code symbol and each multiplexed light beam in a light beam set; the light beam set comprises orbital angular momentum multiplexed light beams formed by superimposing different orders and weights of orbital angular momentum; obtaining the multiplexed light beam according to a spiral phase pattern; obtaining an interference light beam by coaxially interfering the multiplexed light beam and a Gaussian plane wave; obtaining an interference light beam after interference by allowing the interference light beam to pass through atmospheric interference; inputting an intensity pattern of the interference light beam after interference into a trained transfer learning network to obtain an orbital angular momentum spectrum; and restoring the image to be transmitted according to the orbital angular momentum spectrum and the preset encoding scheme.The application can improve the encoding capacity and efficiency, reduce the bit error rate, and realize reliable transmission.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical communication, in particular to an optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning. BACKGROUND

[0002] In recent years, as the development of wavelength, phase, amplitude, frequency and polarization of the physical resource dimension of the light beam has reached the upper limit, in order to further meet the demand of high speed and high bandwidth communication, it is necessary to seek new ways to increase the channel capacity. The orbital angular momentum (OAM) beam, the OAM eigenvalue corresponds to different OAM modes, and the OAM beams with different topological charge numbers are orthogonal to each other. This characteristic provides a new dimension for information transmission of optical communication, which can greatly improve the channel capacity and communication rate of the communication system. In the laboratory, it is difficult to generate vortex beams with large topological charge. Therefore, how to use limited OAM mode values for encoding to realize large capacity and high speed communication, and improve the encoding capacity and efficiency is a problem worth considering.

[0003] Some special cases such as conjugate orbital angular momentum multiplexed with different weights have no difference or the difference is difficult to distinguish with the naked eye. When the weight difference of the superimposed conjugate orbital angular momentum is small, similar situations also occur. Therefore, how to increase the difference of the intensity patterns of these multiplexed beams, the encoding capacity and efficiency, and reduce the error rate are also problems that need to be further considered. SUMMARY

[0004] The purpose of the present application is to provide an optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning, which can realize reliable transmission by improving the encoding capacity and efficiency and reducing the error rate.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] In a first aspect, the present application provides an optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning based on orbital angular momentum, comprising:

[0007] Converting a binary bit stream corresponding to a to-be-transmitted image into a plurality of symbol codes according to a preset encoding scheme; the preset encoding scheme includes a one-to-one correspondence relationship between each symbol code and each orbital angular momentum multiplexed beam in a beam set; the beam set includes a plurality of orbital angular momentum multiplexed beams formed by superimposing each preset orbital angular momentum order with each preset superposition weight;

[0008] According to the spiral phase pattern corresponding to any one symbol code, the orbital angular momentum multiplexed beam corresponding to the symbol code is obtained;

[0009] The orbital angular momentum multiplexed beam corresponding to the symbol symbol is coaxially interfered with a Gaussian plane wave to obtain an interference beam;

[0010] The interference beam passes through an atmospheric disturbance simulated by an atmospheric turbulence phase screen to obtain an interfered interference beam;

[0011] The receiving end collects the intensity map of the interfered interference beam by using a CCD camera as an image collection device, and inputs the collected intensity map into the trained transfer learning network to obtain the orbital angular momentum spectrum of the interfered interference beam.

[0012] The orbital angular momentum spectrum of the interfered interference beam and a preset encoding scheme are used to recover the image to be transmitted.

[0013] Optionally, the binary bit stream corresponding to the image to be transmitted is converted into a plurality of symbol symbols according to the preset encoding scheme, specifically including:

[0014] The binary bit stream corresponding to the image to be transmitted is obtained by performing binary encoding on the image to be transmitted.

[0015] The bit stream segment in the binary bit stream corresponding to the image to be transmitted is converted into a symbol symbol according to the preset encoding scheme to obtain a plurality of symbol symbols; the bit stream segment is composed of n consecutive bit streams; n is a positive integer greater than 1.

[0016] Optionally, the preset encoding scheme includes a one-to-one correspondence relationship between 2 n symbol symbols and 2 n orbital angular momentum multiplexed beams in the beam set.

[0017] Optionally, the orbital angular momentum multiplexed beam corresponding to the symbol symbol is obtained according to the spiral phase map corresponding to any one symbol symbol, specifically including:

[0018] The spiral phase map corresponding to the symbol symbol is loaded on a spatial light modulator to obtain the orbital angular momentum multiplexed beam corresponding to the symbol symbol.

[0019] Optionally, the orbital angular momentum multiplexed beam corresponding to the symbol symbol is coaxially interfered with a Gaussian plane wave to obtain an interference beam, specifically as follows:

[0020] The orbital angular momentum multiplexed beam corresponding to the symbol symbol modulated by the spatial light modulator is coaxially interfered with a Gaussian plane wave to obtain an interference beam.

[0021] Optionally, the method for constructing the atmospheric turbulence phase screen, specifically as follows:

[0022] The phase power spectrum of the random phase screen is obtained through the power spectrum of the simulated atmospheric turbulence, and the atmospheric turbulence phase screen is constructed based on the phase power spectrum of the random phase screen.

[0023] Optionally, the training process of the transfer learning network specifically comprises:

[0024] Obtaining a sample image and an orbital angular momentum spectrum of the sample image;

[0025] Converting a binary bit stream corresponding to the sample image into a plurality of symbol signs according to a preset encoding scheme;

[0026] Obtaining an orbital angular momentum multiplexed light beam corresponding to the symbol sign according to a spiral phase pattern corresponding to any one of the symbol signs;

[0027] Obtaining a sample interference light beam by coaxially interfering the orbital angular momentum multiplexed light beam corresponding to the symbol sign and a Gaussian plane wave;

[0028] Obtaining an interference sample interference light beam by subjecting the sample interference light beam to atmospheric interference simulated by an atmospheric turbulence phase screen;

[0029] Receiving an intensity pattern of the interference sample interference light beam by a CCD camera as an image acquisition device;

[0030] Training a transfer learning network according to the collected intensity pattern and the orbital angular momentum spectrum of the sample image, with the orbital angular momentum spectrum of the sample image as a label, to obtain a trained transfer learning network.

[0031] Optionally, the transfer learning network is a transfer learning architecture based on VGG16.

[0032] According to the specific embodiments provided in the present application, the following technical effects are disclosed:

[0033] The present application provides an optical communication method using orbital angular momentum multiplexing encoding and transfer learning decoding. The method obtains an interference light beam by coaxially interfering an orbital angular momentum multiplexed light beam corresponding to a to-be-transmitted image and a Gaussian plane wave, uses the orbital angular momentum multiplexed light beam and the plane wave interference method to increase the light intensity difference of the orbital angular momentum multiplexed light beam, thereby further improving the recognition accuracy of the transfer learning network, reducing the bit error rate, and realizing reliable transmission. The previous encoding symbols do not use the weight encoding of the OAM mode, and only three OAM modes can only encode seven symbol signs. However, the preset encoding scheme of the present application uses the weight encoding of the OAM mode, and a limited OAM mode can encode a plurality of symbol signs, thereby improving the encoding capacity and efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and all other drawings obtained by those of ordinary skill in the art without creative effort based on these drawings also belong to the protection scope of the present application.

[0035] Figure 1 The flow chart of the optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning provided by the embodiments of the present application is shown in the figure.

[0036] Figure 2 The schematic diagram of the optical communication device using orbital angular momentum multiplexing encoding and decoding based on transfer learning provided by the embodiments of the present application is shown in the figure.

[0037] Figure 3 The intensity distribution diagram of the Laguerre Gaussian beam of orbital angular momentum multiplexing without plane wave interference provided by the embodiments of the present application is shown in the figure.

[0038] Figure 4 The interference intensity distribution diagram of the orbital angular momentum multiplexing beam and the plane wave after interference provided by the embodiments of the present application is shown in the figure.

[0039] Figure 5 The one-to-one correspondence relationship between the interference intensity distribution diagram of the orbital angular momentum multiplexing beam and the plane wave after interference and the code symbol with different weight multiplexing provided by the embodiments of the present application is shown in the figure.

[0040] Figure 6 The schematic diagram of the transfer learning network for orbital angular momentum spectrum analysis provided by the embodiments of the present application is shown in the figure.

[0041] Figure 7 The schematic diagram of the hierarchical simulation of atmospheric turbulence provided by the embodiments of the present application is shown in the figure.

[0042] Figure 8 The schematic diagram of the transfer learning architecture provided by the embodiments of the present application is shown in the figure. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort also belong to the protection scope of the present application.

[0044] The above purposes, features and advantages of the present application can be more obvious and easy to understand. The present application will be further described in detail below with reference to the drawings and specific embodiments.

[0045] The different mode values of the vortex beam are completely orthogonal, and the vortex beams with different OAM mode values (orders of orbital angular momentum) can be multiplexed as channels with different digital information. Traditional orbital angular momentum multiplexing is coaxial interference of vortex beams with different OAM mode values, and the weights of different OAM mode values are all 1. However, vortex beams with large topological charge are usually difficult to generate in the laboratory, and it is also difficult to identify them at the receiving end when they are used for communication. Therefore, the application introduces the weight of the superposition of different vortex beams as one dimension of coding, adds positive and negative superposition, and introduces the idea of interference. It is specified that the weight of the superposition of vortex beams carrying different OAM mode values is 1. At this time, the limited OAM mode value can be used for coding to realize high-capacity and high-speed communication, coding capacity and efficiency. When using orbital angular momentum communication, an important issue is how to quickly and accurately identify the OAM mode value of the different vortex beams at the receiving end to achieve demodulation. Since the intensity distribution of the vortex beam in the composite state is generally different after multiplexing of vortex beams with different OAM mode values, the detection and identification of the OAM mode value at the receiving end can be regarded as an image classification problem. In recent years, the convolution neural network (CNN) in deep learning has made great progress in image classification and target detection due to its powerful feature extraction capability. Compared with traditional vortex beam detection methods, the deep learning method does not require complex equipment, has high identification accuracy and fast identification speed, and therefore has been widely used in the field of optical communication. Based on this, the application provides an optical communication method using orbital angular momentum multiplexing coding and decoding based on transfer learning, as shown in Figure 1 and Figure 6 The method comprises the following steps:

[0046] Step 201: converting a binary bit stream corresponding to a to-be-transmitted image into a plurality of code symbols according to a preset coding scheme; the preset coding scheme comprises a one-to-one correspondence relationship between each code symbol and each orbital angular momentum multiplexed light beam in a light beam set; the light beam set comprises a plurality of orbital angular momentum multiplexed light beams formed by superimposing each order of a preset orbital angular momentum with each preset superposition weight. For example, for any order of a preset orbital angular momentum, the order is superimposed with each preset weight to obtain a plurality of orbital angular momentum multiplexed light beams corresponding to the order. Similarly, the same operation is performed on other orders to finally form the light beam set.

[0047] Step 202: obtaining an orbital angular momentum multiplexed light beam corresponding to any one code symbol according to a spiral phase map corresponding to the code symbol. Specifically, there is a one-to-one mapping relationship between the code symbol and the orbital angular momentum multiplexed light beam corresponding to the to-be-transmitted image. The spiral phase map of the orbital angular momentum multiplexed light beam corresponding to each code symbol is loaded on a spatial light modulator to generate an orbital angular momentum multiplexed light beam.

[0048] Step 203: Coaxially interfere the OAM multiplexed beam corresponding to the symbol symbol and the Gaussian plane wave to obtain an interference beam.

[0049] Step 204: The interference beam passes through the atmospheric disturbance simulated by the atmospheric turbulence phase screen to obtain an interference beam after disturbance.

[0050] Step 205: The receiving end collects the intensity map of the interference beam after disturbance by a CCD camera as an image acquisition device, and inputs the collected intensity map into the trained transfer learning network to obtain the orbital angular momentum spectrum of the interference beam after disturbance. The orbital angular momentum spectrum contains each order and the weight of the order.

[0051] Step 206: According to the orbital angular momentum spectrum of the interference beam after disturbance and the preset encoding scheme, the image to be transmitted is recovered.

[0052] In actual application, the binary bit stream corresponding to the image to be transmitted is converted into a plurality of symbol symbols according to the preset encoding scheme, which specifically includes:

[0053] The binary encoding of the image to be transmitted is performed to obtain the binary bit stream corresponding to the image to be transmitted.

[0054] The bit stream segment in the binary bit stream corresponding to the image to be transmitted is converted into a symbol symbol according to the preset encoding scheme to obtain a plurality of symbol symbols; the bit stream segment is composed of n consecutive bit streams; n is a positive integer greater than 1. When n is 5, the preset encoding scheme is specifically shown in Table 1.

[0055] Table 1: Preset encoding scheme

[0056] Symbol encoding Composite vortex beam Weight of beam superposition Symbol encoding Composite vortex beam Weight of beam superposition 00000 L1 = -2, L2 = 2, L3 = 1 (0，0，0) 10000 L1 = -2, L3 = 1 (0.4，0.6) 00001 L1 = -2, L2 = 2, L3 = 1 (0，0，1) 10001 L1 = -2, L3 = 1 (0.6，0.4) 00010 L1 = -2, L2 = 2, L3 = 1 (0，1，0) 10010 L1 = -2, L3 = 1 (0.1，0.9) 00011 L1 = -2, L2 = 2, L3 = 1 (1，0，0) 10011 L2 = 2, L3 = 1 (0.9，0.1) 00100 L1 = -2, L2 = 2 (0.1，0.9) 10100 L2 = 2, L3 = 1 (0.5，0.5) 00101 L1 = -2, L2 = 2 (0.9，0.1) 10101 L2 = 2, L3 = 1 (0.3，0.7) 00110 L1 = -2, L2 = 2 (0.5，0.5) 10110 L2 = 2, L3 = 1 (0.7，0.3) 00111 L1 = -2, L2 = 2 (0.3，0.7) 10111 L2 = 2, L3 = 1 (0.4，0.6) 01000 L1 = -2, L2 = 2 (0.7，0.3) 11000 L2 = 2, L3 = 1 (0.6，0.4) 01001 L1 = -2, L2 = 2 (0.4，0.6) 11001 L1 = -2, L2 = 2, L3 = 1 (0.1，0.7，0.2) 01010 L1 = -2, L2 = 2 (0.6，0.4) 11010 L1 = -2, L2 = 2, L3 = 1 (0.7，0.1，0.2) 01011 L1 = -2, L3 = 1 (0.1，0.9) 11011 L1 = -2, L2 = 2, L3 = 1 (0.1，0.2，0.7) 01100 L1 = -2, L3 = 1 (0.9，0.1) 11100 L1 = -2, L2 = 2, L3 = 1 (0.3，0.3，0.4) 01101 L1 = -2, L3 = 1 (0.5，0.5) 11101 L1 = -2, L2 = 2, L3 = 1 (0.1，0.8，0.1) 01110 L1 = -2, L3 = 1 (0.3，0.7) 11110 L1 = -2, L2 = 2, L3 = 1 (0.8，0.1，0.1) 01111 Figure 3 (0.7，0.3) 11111 Figure 3 (0.1，0.1，0.8)

[0057] In actual application, the preset encoding scheme includes a one-to-one correspondence between 2n symbol symbols and 2n orbital angular momentum multiplexed beams in the beam set.

[0058] In actual application, according to the spiral phase map corresponding to any one symbol symbol, the orbital angular momentum multiplexed beam corresponding to the symbol symbol is obtained; the orbital angular momentum multiplexed beam corresponding to the symbol symbol and the Gaussian plane wave are coaxially interfered to obtain an interference beam, which specifically includes:

[0059] The light field expression of a Laguerre-Gaussian (LG) beam transmitted along the z-axis in a cylindrical coordinate system is:

[0060]

[0061] Where P is the radial index, λ is the wavelength, and l is the OAM mode value. is the waist radius of the LG beam at z, w0is the waist radius of the fundamental Gaussian beam at z = 0, z R = πw0 2 / λ is the Rayleigh range, is the wave number of the beam, is the Gouy phase, is the normalized Laguerre polynomial. When p = 0, is 1, in which case the light field expression of the LG beam is:

[0062]

[0063] The light field expression of the vortex beam can be expanded according to the following formula:

[0064]

[0065] wherein,

[0066]

[0067] The light field intensity of the lth spiral harmonic is:

[0068]

[0069] Therefore, the intensity weight of each OAM mode in the orbital angular momentum multiplexing beam is represented by the following formula:

[0070]

[0071] When p = 0, the LG beams with different OAM mode values are multiplexed with certain weights to produce the orbital angular momentum multiplexing beam with weight multiplexing, and its light field expression is:

[0072]

[0073] The Laguerre Gaussian beams with three OAM mode values of {-2, 2, 1} are taken as an example to multiplex different weights of OAM, and the Laguerre Gaussian beams with three OAM mode values are respectively superimposed with weights (0, 0, 0), (0, 0, 1), (0, 1, 0), (1, 0, 0), (0.1, 0.9, 0), (0.9, 0.1, 0), (0.5, 0.5, 0), (0.3, 0.7, 0), (0.7, 0.3, 0), (0.4, 0.6, 0), (0.6, 0.4, 0), (0.1, 0, 0.9), (0.9, 0, 0.1), (0.5, 0, 0.5), (0.3, 0, 0.7), (0.7, 0, 0.3), (0.4, 0, 0.6), (0.6, 0, 0.4), (0, 0.1, 0.9), (0, 0.9, 0.1), (0, 0.5, 0.5), (0, 0.3, 0.7), (0, 0.7, 0.3), (0, 0.4, 0.6), (0, 0.6, 0.4), (0.1, 0.7, 0.2), (0.7, 0.1, 0.2), (0.1, 0.2, 0.7), (0.3, 0.3, 0.4), (0.1, 0.8, 0.1), (0.8, 0.1, 0.1), (0.1, 0.1, 0.8) to be superimposed, and 32 kinds of intensity patterns can be generated.

[0074] Generally, the intensity distribution of the multiplexed vortex beams with different OAM mode values and different weights is generally different, but there are special cases. For example, the intensity patterns of the multiplexed vortex beams with conjugate orbital angular momentum -2 and 2 and weights (0, 1) and (1, 0) respectively have no difference. Similar cases also occur when the multiplexed vortex beams with conjugate orbital angular momentum -2 and 2 and weights (0.1, 0.9) and (0.9, 0.1) respectively. Similar cases also occur when the multiplexed vortex beams with conjugate orbital angular momentum -2 and 2 and weights (0.4, 0.6), (0.6, 0.4), (0.5, 0.5), (0.3, 0.7), (0.7, 0.3) respectively. If the multiplexed vortex beams are directly transmitted, the error rate of the decoding module will inevitably increase. Therefore, the plane wave and the vortex beam with weight superposition are coaxially interfered to generate an interference beam to increase the difference in the light intensity of the vortex beam with weight superposition. Taking the multiplexed vortex beams with OAM mode values {-2, 2} and weights (0, 1) and (1, 0) as an example, before the interference, as shown in FIG. 8, Figure 3 , Figure 3 (a) of FIG. 8 shows the intensity distribution of the multiplexed Laguerre Gaussian beam without plane wave interference when the symbol code is 00000, the preset orbital angular momentum order is L1=-2, L2=2, L3=1, and the preset superposition weight is (0, 0, 0), Figure 3Fig. 6 (b) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00001, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0, 1), Figure 3 Fig. 6 (c) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00010, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 1, 0), Figure 3 Fig. 6 (d) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (1, 0, 0), Figure 3 Fig. 6 (e) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00100, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.1, 0.9, 0), Figure 3 Fig. 6 (f) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00101, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.9, 0.1, 0), Figure 3 Fig. 6 (g) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00110, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.5, 0.5, 0), Figure 3 Fig. 6 (h) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 00111, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.3, 0.7, 0), Figure 3 Fig. 6 (i) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01000, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.7, 0.3, 0), Figure 3 Fig. 6 (j) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01001, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.4, 0.6, 0), Figure 3 Fig. 6 (k) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01010, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.6, 0.4, 0), Figure 3 Fig. 6 (l) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01011, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.1, 0, 0.9), Figure 3Fig. 1 (m) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01100, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.9, 0, 0.1), Figure 3 Fig. 1 (n) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01101, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.5, 0, 0.5), Figure 3 Fig. 1 (o) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01110, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.3, 0, 0.7), Figure 3 Fig. 1 (p) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 01111, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.7, 0, 0.3), Figure 3 Fig. 1 (q) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10000, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.4, 0, 0.6), Figure 3 Fig. 1 (r) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10001, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.6, 0, 0.4), Figure 3 Fig. 1 (s) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10010, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.1, 0, 0.9), Figure 3 Fig. 1 (t) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.9, 0.1), Figure 3 Fig. 1 (u) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10100, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.5, 0.5), Figure 3 Fig. 1 (v) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10101, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.3, 0.7), Figure 3 Fig. 1 (w) shows the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference when the symbol coding is 10110, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.7, 0.3),Figure 3 In the diagram, (x) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, where the symbol encoding is 10111, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.4, 0.6). Figure 3 The value (y) represents the intensity distribution of the orbital angular momentum multiplexed Laguerre Gaussian beam without plane wave interference, with symbol encoding 11000, L1 = -2, L2 = 2, L3 = 1, and superposition weight (0, 0.6, 0.4). Figure 3 The value (z) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11001, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.1, 0.7, 0.2). Figure 3 (A) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11010, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.7, 0.1, 0.2). Figure 3 (B) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11011, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.1, 0.2, 0.7). Figure 3 (C) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11100, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.3, 0.3, 0.4). Figure 3 (D) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11101, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.1, 0.8, 0.1). Figure 3 (E) represents the intensity distribution of a Laguerre Gaussian beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11110, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.8, 0.1, 0.1). Figure 3 (F) represents the intensity distribution of a Laguerreotype beam with orbital angular momentum multiplexing without plane wave interference, with symbol encoding 11111, L1 = -2, L2 = 2, L3 = 1, and superposition weights of (0.1, 0.1, 0.8). The intensity distribution of both beams exhibits a ring-shaped distribution with a central dark core, and the rings are all the same size, making it impossible to directly distinguish the OAM mode values ​​from their intensity distribution. After the two multiplexed beams are coaxially interfered with the plane wave, as shown... Figure 3 As shown, Figure 3 In diagram (a), the interference intensity distribution of the orbital angular momentum multiplexed beam after interference with a plane wave is shown when the symbol code is 00000, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0, 0).Figure 3 Fig. 2 (b) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00001, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0, 1), Figure 3 Fig. 2 (c) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00010, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 1, 0), Figure 3 Fig. 2 (d) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (1, 0, 0), Figure 3 Fig. 2 (e) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00100, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.1, 0.9, 0), Figure 3 Fig. 2 (f) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00101, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.9, 0.1, 0), Figure 3 Fig. 2 (g) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00110, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.5, 0.5, 0), Figure 3 Fig. 2 (h) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00111, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.3, 0.7, 0), Figure 3 Fig. 2 (i) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01000, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.7, 0.3, 0), Figure 4 Fig. 2 (j) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01001, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.4, 0.6, 0), Figure 4 Fig. 2 (k) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01010, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.6, 0.4, 0), Figure 4 Fig. 2 (l) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01011, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.1, 0, 0.9), Figure 4Fig. 2 (m) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 01100, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.9, 0, 0.1), Figure 4 Fig. 2 (n) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 01101, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.5, 0, 0.5), Figure 4 Fig. 2 (o) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 01110, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.3, 0, 0.7), Figure 4 Fig. 2 (p) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 01111, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.7, 0, 0.3), Figure 4 Fig. 2 (q) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10000, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.4, 0, 0.6), Figure 4 Fig. 2 (r) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10001, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.6, 0, 0.4), Figure 4 Fig. 2 (s) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10010, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.1, 0.9), Figure 4 Fig. 2 (t) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.9, 0.1), Figure 4 Fig. 2 (u) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10100, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.5, 0.5), Figure 4 Fig. 2 (v) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10101, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.3, 0.7), Figure 4 Fig. 2 (w) shows the interference intensity distribution diagram of the orbital angular momentum multiplexed beam and the plane wave after interference when the symbol coding is 10110, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.7, 0.3), Figure 4Fig. 1 (x) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 10111, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.4, 0.6), Figure 4 Fig. 1 (y) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11000, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.6, 0.4), Figure 4 Fig. 1 (z) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11001, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.1, 0.7, 0.2), Figure 4 Fig. 1 (A) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11010, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.7, 0.1, 0.2), Figure 4 Fig. 1 (B) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.1, 0.2, 0.7), Figure 4 Fig. 1 (C) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11100, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.3, 0.3, 0.4), Figure 4 Fig. 1 (D) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11101, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.1, 0.8, 0.1), Figure 4 Fig. 1 (E) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11110, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.8, 0.1, 0.1), Figure 4 Fig. 1 (F) shows the intensity distribution of the interference light after the orbital angular momentum multiplexed beam and the plane wave interfere, where the symbol coding is 11111, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0.1, 0.1, 0.8), the interference pattern shows a fork-shaped distribution with a central dark spot, the difference is that the opening direction of the former fork-shaped stripe is upward, and the opening direction of the latter fork-shaped stripe is downward, the effect of interference is to improve the spectral analysis accuracy of the convolutional neural network in the decoding module and reduce the bit error rate.

[0075] The expression of the intensity distribution of the Laguerre-Gaussian beam after weight multiplexing and plane wave interference is as follows:

[0076] I = |E1 + E2| 2

[0077] = |∑ l w l E LG (r,φ,z)+e -ikx | 2

[0078] 32 kinds of multiplexed light beams correspond to 32 kinds of interference patterns after plane wave interference, each interference pattern corresponds to a code symbol, only three OAM modes can encode 32 code symbols, realizing 5bit transmission. The weight of the superposition of three different OAM mode values of Laguerre Gaussian beams is used for encoding, the weight information is effectively utilized, the capacity and efficiency of the limited OAM mode value are encoded, and the difference of the multiplexed light intensity distribution is increased by the method of plane wave interference, so as to reduce the error rate of the decoding module, realize reliable transmission, realize a 32ary orbital angular momentum multiplexing and coding and decoding method based on transfer learning, which can greatly improve the channel capacity of the communication system.

[0079] Specifically, the Laguerre Gaussian beams of weight multiplexing and plane wave interference are simulated, the different light intensity of the interference pattern is used for encoding, 32 kinds of multiplexed intensity patterns correspond to 32 kinds of interference patterns, and the data "00000-00001-00010-00011-00100-00101-00110-00111-01000-01001-01010-01011-01100-01101-01110-01111-10000-10001-10010-10011-10100-10101-10110-10111-11000-11001-11010-11011-11100-11101-11110-11111" is encoded into 32 kinds of interference patterns, Figure 4 The one-to-one correspondence between the interference light intensity distribution of the orbital angular momentum multiplexed light beams and the plane wave after interference and the code symbol is given, Figure 4 In (a), the symbol code is 00000, L1=-2, L2=2, L3=1, and the interference light intensity distribution of the vortex beam and the plane wave after interference when the superposition weight is (0, 0, 0) is shown, Figure 4 In (b), the symbol code is 00001, L1=-2, L2=2, L3=1, and the interference light intensity distribution of the orbital angular momentum multiplexed light beams and the plane wave after interference when the superposition weight is (0, 0, 1) is shown, Figure 4 In (c), the symbol code is 00010, L1=-2, L2=2, L3=1, and the interference light intensity distribution of the orbital angular momentum multiplexed light beams and the plane wave after interference when the superposition weight is (0, 1, 0) is shown, Figure 4Fig. 6 (d) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (1, 0, 0), Figure 4 Fig. 6 (e) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00100, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.1, 0.9, 0), Figure 4 Fig. 6 (f) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00101, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.9, 0.1, 0), Figure 5 Fig. 6 (g) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00110, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.5, 0.5, 0), Figure 5 Fig. 6 (h) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 00111, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.3, 0.7, 0), Figure 5 Fig. 6 (i) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01000, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.7, 0.3, 0), Figure 5 Fig. 6 (j) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01001, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.4, 0.6, 0), Figure 5 Fig. 6 (k) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01010, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.6, 0.4, 0), Figure 5 Fig. 6 (l) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01011, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.1, 0, 0.9), Figure 5 Fig. 6 (m) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01100, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.9, 0, 0.1), Figure 5 Fig. 6 (n) shows the intensity distribution of the interference light after the interference between the orbital angular momentum multiplexed light beam and the plane wave when the symbol code is 01101, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.5, 0, 0.5), Figure 5Fig. 2 (o) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 01110, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.3, 0, 0.7), Figure 5 Fig. 2 (p) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 01111, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.7, 0, 0.3), Figure 5 Fig. 2 (q) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10000, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.4, 0, 0.6), Figure 5 Fig. 2 (r) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10001, L1 = -2, L2 = -2, L3 = 1, and the superposition weight is (0.6, 0, 0.4), Figure 5 Fig. 2 (s) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10010, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.1, 0.9), Figure 5 Fig. 2 (t) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10011, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.9, 0.1), Figure 5 Fig. 2 (u) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10100, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.5, 0.5), Figure 5 Fig. 2 (v) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10101, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.3, 0.7), Figure 5 Fig. 2 (w) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10110, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.7, 0.3), Figure 5 Fig. 2 (x) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 10111, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.4, 0.6), Figure 5 Fig. 2 (y) shows the intensity distribution of the interference light after the interference of the orbital angular momentum multiplexed light beam and the plane wave when the symbol coding is 11000, L1 = -2, L2 = 2, L3 = 1, and the superposition weight is (0, 0.6, 0.4), Figure 5The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11001, L1=-2, L2=2, L3=1, and the superposition weight is (0.1, 0.7, 0.2), Figure 5 The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11010, L1=-2, L2=2, L3=1, and the superposition weight is (0.7, 0.1, 0.2), Figure 5 The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11011, L1=-2, L2=2, L3=1, and the superposition weight is (0.1, 0.2, 0.7), Figure 5 The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11100, L1=-2, L2=2, L3=1, and the superposition weight is (0.3, 0.3, 0.4), Figure 5 The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11101, L1=-2, L2=2, L3=1, and the superposition weight is (0.1, 0.8, 0.1), Figure 5 The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11110, L1=-2, L2=2, L3=1, and the superposition weight is (0.8, 0.1, 0.1), Figure 5 The interference light intensity distribution diagram after the orbital angular momentum multiplexed beam and the plane wave interfere when the symbol code is 11111, L1=-2, L2=2, L3=1, and the superposition weight is (0.1, 0.1, 0.8).

[0080] In practical applications, the orbital angular momentum multiplexed beam corresponding to the symbol code is obtained according to the spiral phase pattern corresponding to any one symbol code, and the specific process includes the following steps:

[0081] The spiral phase pattern corresponding to the symbol code is loaded on the spatial light modulator to obtain the orbital angular momentum multiplexed beam corresponding to the symbol code.

[0082] In practical applications, the orbital angular momentum multiplexed beam corresponding to the symbol code and the Gaussian plane wave are coaxially interfered to obtain an interference beam, and the specific process includes the following steps:

[0083] The orbital angular momentum multiplexed beam corresponding to the symbol code after being modulated by the spatial light modulator is coaxially interfered with the Gaussian plane wave to obtain an interference beam.

[0084] In practical applications, the atmospheric turbulence phase screen construction method includes the following steps:

[0085] The phase power spectrum of the random phase screen is obtained by the power spectrum of the simulated atmospheric turbulence, and the atmospheric turbulence phase screen is constructed according to the phase power spectrum of the random phase screen.

[0086] In practical applications, as shown in the figure, the phase power spectrum of the random phase screen is obtained by the power spectrum of the simulated atmospheric turbulence, and the atmospheric turbulence phase screen is constructed according to the phase power spectrum, specifically: Figure 5

[0087] The power spectrum inversion method is used to generate the random phase screen of the turbulence medium by using the Hill-Andrews spatial spectrum:

[0088]

[0089] In the two-dimensional space, for the atmospheric turbulence, a1=1.802, a2=0.254, a1 and a2 are constant and have no practical significance.

[0090]

[0091] Where k l =3.3 / l0, k0=2π / L0, k x and k y are the wave numbers in the x and y directions, respectively, and l0 and L0 represent the inner scale and outer scale of the turbulence, respectively. is the atmospheric turbulence intensity, is the wave number of the light beam.

[0092] The relationship between the phase spectrum and the atmospheric refractive index spectrum can be described as:

[0093]

[0094] The variance of the frequency domain distribution of the random phase screen is:

[0095]

[0096] Where N represents the number of sampling points, and Δx represents the sampling interval.

[0097] The formula for calculating the phase screen in the spatial domain is:

[0098]

[0099] Where FFT represents two-dimensional fast Fourier transform, C N×N is an N×N random phase matrix, which follows a Gaussian distribution, has a mean of 0, and a variance of 1.

[0100] After the interference light beam passes through the simulated atmospheric turbulence phase screen and transmits a certain distance, the electric field expression is:

[0101] ​

[0102] wherein FFT -1 denotes a two-dimensional fast inverse Fourier transform, denotes a Fresnel propagation function. Specifically, when simulating the transmission of an interference beam in an atmospheric turbulence environment, the light waist w0=2.5cm, the wavelength λ=632.8nm, the radial index p=0, the OAM mode number l1=-2, l2=2, l3=1, and the turbulence intensity is the inner size l0=0.003nm, the outer size L0=50m, the phase screen resolution N=300, and the interval Δz between phase screens =100m.

[0103] In actual application, the training process of the transfer learning network specifically includes:

[0104] obtaining a sample image and an orbital angular momentum spectrum of the sample image;

[0105] converting a binary bit stream corresponding to the sample image into a plurality of symbol codes according to a preset encoding scheme;

[0106] obtaining an orbital angular momentum multiplexed light beam corresponding to the symbol code according to a spiral phase pattern corresponding to any one of the symbol codes;

[0107] obtaining a sample interference light beam by coaxially interfering the orbital angular momentum multiplexed light beam corresponding to the symbol code and a Gaussian plane wave;

[0108] obtaining an interference sample interference light beam by subjecting the sample interference light beam to atmospheric interference simulated by an atmospheric turbulence phase screen;

[0109] collecting an intensity pattern of the interference sample interference light beam by a CCD camera as an image collecting device at a receiving end;

[0110] training a transfer learning network by taking the orbital angular momentum spectrum of the sample image as a label and according to the collected intensity pattern and the orbital angular momentum spectrum of the sample image. Specifically, the transfer learning network can be a convolutional neural network. First, the convolutional neural network is trained, and then the trained convolutional neural network is used to process the collected intensity pattern to obtain the orbital angular momentum spectrum of the interference light beam after interference, and then orbital angular momentum spectrum analysis is performed to restore the symbol code corresponding to the collected intensity pattern, thereby realizing decoding. Specifically, the collected interference light intensity distribution pattern (collected intensity pattern) is input into the convolutional neural network trained by a large amount of data. The convolutional neural network realizes orbital angular momentum spectrum analysis according to different intensity patterns, restores binary data according to the one-to-one correspondence between the intensity pattern and the symbol code, thereby restoring the original image information and realizing demodulation.

[0111] In practical applications, when training the convolutional neural network, the data set is constructed according to the light field expression of the orbital angular momentum multiplexing light beam and the light beam after interference with a plane wave after transmission in atmospheric turbulence, the image data set is an interference pattern, and the label is the OAM mode component and its weight corresponding to the interference pattern. The portability of the features extracted by the CNN can be used to extract features from the data set using a pre-trained network as a feature extractor to start training.

[0112] In practical applications, the transfer learning network uses the convolutional base of the VGG16 network trained on ImageNet as a feature extractor, uses a softmax function as a classifier, and uses a VGG16-based transfer learning architecture to perform orbital angular momentum spectrum analysis on the received interference pattern (intensity map of the interfered interference light beam), restores the symbol corresponding to the collected interference pattern to realize decoding. Specifically, as shown in Figure 5 The VGG16-based transfer learning architecture includes a convolution module and a classifier connected in sequence, the classifier includes a Flatten layer, a Dense layer (full connection layer) and a DropOut layer connected in sequence, each convolution base is composed of two convolution layers and a maximum pooling layer connected in sequence, the Flatten layer is used to one-dimensionize the multi-dimensional input, and the DropOut layer is added to prevent overfitting. The convolution base in the architecture is frozen, that is, the weight of one or more layers remains unchanged during the training process.

[0113] In practical applications, when training the VGG16-based transfer learning architecture, the image of the interference light beam after transmission through the simulated atmospheric turbulence is used to construct a data set, and the VGG16-based transfer learning architecture is trained.

[0114] The present application provides an orbital angular momentum weight multiplexing encoding optical communication method based on transfer learning. First, the image to be transmitted is converted into a binary code stream and then orbital angular momentum encoding is performed. Each five bits of binary information corresponds to a symbol, and a plurality of symbols corresponding to the image to be transmitted are obtained. A spatial light modulator loads the spiral phase pattern corresponding to the symbol, thereby generating an orbital angular momentum multiplexing light beam corresponding to the symbol. Then, the orbital angular momentum multiplexing light beam corresponding to the symbol is coaxially interfered with a Gaussian plane wave to increase the intensity pattern difference between orbital angular momentum multiplexing light beams with different weights. The interference light beam is transmitted through a simulated turbulence phase screen, and the interference pattern after transmission is collected at the receiving end. A trained convolutional neural network (transfer learning network) is used to perform orbital angular momentum spectrum analysis on the received interference light beam, classify the orbital angular momentum multiplexing light beams with different weights, restore the symbol corresponding to the interference pattern, restore the binary code stream, integrate and classify the data information, and obtain the original image information.

[0115] Compared with the prior art, the application has the following beneficial effects:

[0116] The weight information of the Laguerre Gaussian beam superposition of different OAM mode values is fully utilized for coding, so that the coding efficiency of the digital signal is further improved in the case of limited OAM mode values, the method of interference between the orbital angular momentum multiplexing beam and the plane wave is utilized to increase the difference in the light intensity performance of the vortex beam of the weight multiplexing, so that the identification accuracy of the transfer learning network is further improved at the receiving end, the bit error rate is reduced, and reliable transmission is realized.

[0117] Based on the same inventive concept, the embodiment of the application also provides a kind of light communication device for realizing the light communication method of utilizing orbital angular momentum multiplexing coding and based on transfer learning decoding described above using orbital angular momentum multiplexing coding and based on transfer learning decoding.The device, as shown in Figure 5 Figure 5 Figure 5 Figure 5 Figure 7 Figure 8 Figure 2 It includes:

[0118] The encoding module is used to convert the binary bit stream corresponding to the image to be transmitted into a plurality of symbol codes according to a preset encoding scheme; the preset encoding scheme includes a one-to-one correspondence between each symbol code and each orbital angular momentum multiplexing beam in the beam set; the beam set includes a plurality of orbital angular momentum multiplexing beams formed by superimposing each preset orbital angular momentum order with each preset superposition weight.

[0119] The orbital angular momentum multiplexing module is used to obtain the orbital angular momentum multiplexing beam corresponding to the symbol code according to the spiral phase map corresponding to any one symbol code; and coaxially interferes the orbital angular momentum multiplexing beam corresponding to the symbol code with a Gaussian plane wave to obtain an interference beam.

[0120] The beam transmission module is used to obtain the interference beam after interference by the atmospheric interference simulated by the atmospheric turbulence phase screen.

[0121] The beam receiving module is used to collect the intensity map of the interference beam after interference by the CCD camera as the image acquisition device at the receiving end, and input the collected intensity map into the trained transfer learning network to obtain the orbital angular momentum spectrum of the interference beam after interference.

[0122] The beam decoding module is used to recover the image to be transmitted according to the orbital angular momentum spectrum of the interference beam after interference and the preset encoding scheme.

[0123] As an optional implementation, the light communication device using orbital angular momentum multiplexing coding and based on transfer learning decoding further includes an image preprocessing module for binary encoding the image to be transmitted to obtain the binary bit stream corresponding to the image to be transmitted.

[0124] Any technical features in the above embodiments can be combined, and for the sake of brevity, not all possible combinations are described above, however, it should be understood that the application encompasses all possible combinations of the technical features unless such a combination is not technically possible.

[0125] The principles and implementation manners of the present application are described herein by using specific examples, and the above embodiments are only used to help understand the method of the present application and its core idea; meanwhile, according to the idea of the present application, the specific implementation manners and application scopes will be changed by those skilled in the art. In conclusion, the content of the present specification should not be understood as a limitation of the present application.

Claims

1. An optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning, characterized by, The optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning comprises: According to a preset encoding scheme, a binary bit stream corresponding to an image to be transmitted is converted into a plurality of symbol signs; the preset encoding scheme comprises a one-to-one correspondence relationship between each symbol sign and each orbital angular momentum multiplexing light beam in a light beam set; the light beam set comprises a plurality of orbital angular momentum multiplexing light beams formed by superimposing each preset orbital angular momentum order with each preset superposition weight; According to a spiral phase map corresponding to any one symbol sign, an orbital angular momentum multiplexing light beam corresponding to the symbol sign is obtained; The orbital angular momentum multiplexing light beam corresponding to the symbol sign and a Gaussian plane wave are coaxially interfered to obtain an interference light beam; The interference light beam passes through atmospheric interference simulated by an atmospheric turbulence phase screen to obtain an interfered interference light beam; A receiving end acquires an intensity map of the interfered interference light beam by using a CCD camera as an image acquisition device, inputs the acquired intensity map into a trained transfer learning network to obtain an orbital angular momentum spectrum of the interfered interference light beam, and restores the image to be transmitted according to the orbital angular momentum spectrum of the interfered interference light beam and the preset encoding scheme. According to a preset encoding scheme, a binary bit stream corresponding to an image to be transmitted is converted into a plurality of symbol signs, specifically comprising: 2.The optical communication method using orbital angular momentum multiplexing encoding and migration learning based decoding of claim 1, wherein, The binary bit stream corresponding to the image to be transmitted is obtained by binary encoding the image to be transmitted; According to a preset encoding scheme, a binary bit stream corresponding to an image to be transmitted is converted into a plurality of symbol signs; the preset encoding scheme comprises a one-to-one correspondence relationship between each symbol sign and each orbital angular momentum multiplexing light beam in a light beam set; the light beam set comprises a plurality of orbital angular momentum multiplexing light beams formed by superimposing each preset orbital angular momentum order with each preset superposition weight. According to a spiral phase map corresponding to any one symbol sign, an orbital angular momentum multiplexing light beam corresponding to the symbol sign is obtained, specifically comprising: 3.The optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning according to claim 2, wherein, The preset coding scheme includes 2 n one-to-one correspondence between 2 n orbital angular momentum multiplexing beams in the light beam set. 4.The optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning according to claim 1, wherein, The spiral phase map corresponding to the symbol sign is loaded on a spatial light modulator to obtain the orbital angular momentum multiplexing light beam corresponding to the symbol sign. The orbital angular momentum multiplexing light beam corresponding to the symbol sign and a Gaussian plane wave are coaxially interfered to obtain an interference light beam, specifically comprising: 5.The optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning according to claim 4, wherein, The orbital angular momentum multiplexing light beam corresponding to the symbol sign and a Gaussian plane wave are coaxially interfered to obtain an interference light beam, specifically comprising: The method for constructing the atmospheric turbulence phase screen specifically comprises: 6.The optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning according to claim 1, wherein, A phase power spectrum of a random phase screen is obtained from a power spectrum of the simulated atmospheric turbulence, and the atmospheric turbulence phase screen is constructed according to the phase power spectrum of the random phase screen. The training process of the transfer learning network specifically comprises: 7.The optical communication method using orbital angular momentum multiplexing encoding and decoding based on transfer learning of claim 1, wherein, A sample image and an orbital angular momentum spectrum of the sample image are obtained; According to a preset encoding scheme, a binary bit stream corresponding to an image to be transmitted is converted into a plurality of symbol signs; According to a spiral phase map corresponding to any one symbol sign, an orbital angular momentum multiplexing light beam corresponding to the symbol sign is obtained; The orbital angular momentum multiplexing light beam corresponding to the symbol sign and a Gaussian plane wave are coaxially interfered to obtain a sample interference light beam; The sample interference light beam passes through atmospheric interference simulated by an atmospheric turbulence phase screen to obtain an interfered sample interference light beam; A receiving end acquires an intensity map of the interfered sample interference light beam by using a CCD camera as an image acquisition device; ​ The sample image is taken as a label, and a transfer learning network is trained according to the collected intensity image and the orbital angular momentum spectrum of the sample image to obtain a trained transfer learning network. 8.The optical communication method using orbital angular momentum multiplexing encoding and migration learning based decoding of claim 1, wherein, The transfer learning network is a transfer learning architecture based on VGG16.

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