Optical communication equipment suitable for deep sea underwater robot

Abstract

The invention relates to the technical field of underwater wireless optical communication, in particular to optical communication equipment suitable for a deep sea underwater robot. The method comprises the following steps: a signal modulation unit loads a data signal needing to be transmitted to Gaussian laser generated by a laser, and loads a modulation signal to the Gaussian laser; the spatial light modulation unit converts the modulated Gaussian laser into a non-diffraction light beam; the optical transmitting unit is used for aligning and directionally transmitting non-diffraction light beams through a PI D control algorithm; the optical receiving unit collects the non-diffracting light beams transmitted from the optical transmitting unit and performs primary focusing on the non-diffracting light beams; the optical noise reduction unit uses a filtering module to remove scattered light of different wavebands, and uses a shading module to further eliminate noise in an area near a non-diffracting beam phase singular point; and the signal demodulation unit demodulates the modulation signal detected by the detector. The laser communication technology is adopted in the design, and the advantages of medium and long distance, high speed and miniaturization are simultaneously met under the condition of low power consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater wireless optical communication, and in particular to an optical communication device suitable for a deep-sea underwater robot. Background Art

[0002] In recent years, as the guidance of the concept of building a community with a shared future for the ocean continues to deepen, underwater communications have gradually become a focus of attention. Traditional underwater communications usually use acoustic communications, but acoustic communications have problems such as low speed, poor safety, high energy consumption, significant multipath effects, and inconsistent speeds in different waters. Therefore, there is an urgent need for an underwater wireless laser communication technology with higher speed, low energy consumption, and high safety. However, underwater wireless laser communications currently generally have problems such as short communication distance and obvious underwater noise. Especially under natural conditions, background light and scattered light of the signal itself will become noise in the underwater wireless laser communication system. Therefore, an optical communication device suitable for deep-sea underwater robots is designed. Summary of the invention

[0003] The purpose of the present invention is to provide an optical communication device suitable for deep-sea underwater robots to solve the problems of low rate, poor safety, high energy consumption, significant multipath effect and inconsistent speed in different waters in acoustic communication proposed in the above background technology.

[0004] To achieve the above object, the present invention provides an optical communication device suitable for a deep-sea underwater robot, comprising:

[0005] A signal modulation unit, wherein the signal modulation unit loads the data signal to be transmitted onto the Gaussian laser generated by the laser, and loads the Gaussian laser with a modulation signal;

[0006] A spatial light modulation unit, wherein the spatial light modulation unit converts the modulated Gaussian laser into a non-diffraction light beam;

[0007] An optical transmitting unit, wherein the optical transmitting unit aligns and directs the emission of a non-diffraction light beam through a PID control algorithm;

[0008] An optical receiving unit, which collects the non-diffraction light beam transmitted from the optical transmitting unit and performs preliminary focusing;

[0009] An optical noise reduction unit, wherein the optical noise reduction unit uses a filter module to remove scattered light of different wavelength bands, and uses a light shielding module to further eliminate noise in the vicinity of a phase singularity of a non-diffracting light beam;

[0010] A signal demodulation unit demodulates the modulated signal detected by the detector to restore the information loaded by the Gaussian laser.

[0011] As a further improvement of the technical solution, the signal modulation unit loads the data signal to be transmitted onto the Gaussian laser generated by the laser, and loads the modulation signal onto the Gaussian laser, including the following steps:

[0012] S1.1. Prepare the data to be transmitted and encode the data;

[0013] S1.2. Select the modulation mode as ASK modulation, and optimize the ASK modulation by considering the attenuation and absorption of the modulation signal;

[0014] S1.3, using the selected modulation method, mapping the encoded data stream to the carrier signal;

[0015] S1.4. Load the modulated signal onto the Gaussian laser generated by the laser.

[0016] As a further improvement of the technical solution, the S1.2, ASK modulation is:

[0017] s(t)=A(t)·cos(2πf c t+β);

[0018] Considering the attenuation and absorption of the modulation signal, the amplitude-shift keying (ASK) modulation is optimized as follows:

[0019] s1(t)=G(t)·A(t)·cos(2πf c t+β);

[0020] Where s(t) represents the modulated signal; A(t) represents the amplitude function; f c represents the carrier frequency; β represents the phase shift; s1(t) represents the modulated signal considering the attenuation and absorption of the modulated signal; G(t) represents the dynamic range adjustment factor, which is used to compensate for the attenuation and absorption of the modulated signal during underwater propagation.

[0021] As a further improvement of the technical solution, the spatial light modulation unit converts the modulated Gaussian laser into a non-diffraction light beam, comprising the following steps:

[0022] S2.1. Determine the order, wavelength and other parameters of the required non-diffraction beam;

[0023] S2.2, use the mathematical software MATLAB to calculate the corresponding phase distribution;

[0024] S2.3, generating a two-dimensional matrix hologram according to the calculated phase distribution;

[0025] S2.4. Load the generated hologram onto the spatial light modulator SLM to ensure that each pixel on the spatial light modulator SLM can be modulated according to the phase delay indicated by the hologram.

[0026] As a further improvement of the technical solution, the optical emission unit aligns and directs the emission of the non-diffraction light beam through a PID control algorithm, comprising the following steps:

[0027] S3.1, set the parameters of the PID control algorithm and initialize the position of the transmitting unit;

[0028] S3.2, using sensors installed around the optical transmitting unit to detect whether the transmitting beam is correctly aimed at the target;

[0029] S3.3, calculating the deviation between the actual position and the target position according to the signal strength fed back by the sensor;

[0030] S3.4, calculating the control signal based on the current error through the PID control algorithm;

[0031] S3.5, transmitting the control signal output by the PID control algorithm to the optical transmitting unit to adjust the angle and position of the transmitting unit;

[0032] S3.6. Repeat steps S3.2 to S3.5 until the position of the optical emitting unit reaches the expected target position and maintains a stable alignment state.

[0033] As a further improvement of the technical solution, in S3.4, the control signal is calculated based on the current error by the PID control algorithm as follows:

[0034]

[0035] Where, u(t) represents the control signal; K p Represents proportional gain; K i Indicates the integral gain; K d represents the differential gain; t represents the time variable; e(t) represents the difference between the actual pointing direction of the current beam and the target pointing direction; τ represents the integral variable.

[0036] As a further improvement of the technical solution, the optical noise reduction unit uses a filter module to remove scattered light of different bands, including the following steps:

[0037] S4.1. Measure the spectral characteristics of the optical signal, determine the main wavelength band of the signal and the wavelength band of the scattered light, record the data of the light intensity changing with the wavelength, analyze the data and mark the signal wavelength band to be retained and the scattered light wavelength band to be removed;

[0038] S4.2. Select the appropriate filter module type according to the results of the spectrum analysis, and determine the center wavelength, bandwidth, and transmittance of the filter module;

[0039] S4.3. Use optical simulation software to simulate the transmittance of the filter module to light of different wavelengths;

[0040] S4.4. Use the gradient descent method to optimize the design parameters of the filter module.

[0041] As a further improvement of the technical solution, the use of the shading module to further eliminate the noise in the vicinity of the phase singularity of the non-diffracting light beam includes the following steps:

[0042] S5.1. Use the numerical simulation software COMSOL Multiphysics to establish a propagation model of a non-diffraction beam, simulate the light field distribution, and identify the position of the phase singularity.

[0043] S5.2. Design the preliminary shape and size of the shading module according to the position of the phase singularity;

[0044] S5.3. Use genetic algorithm to optimize the shape and size of the shading module to ensure that it can accurately cover the phase singularity area, and use finite element analysis to verify whether the design of the shading plate can effectively reduce noise;

[0045] S5.4. Use the particle swarm optimization algorithm to adjust the position of the shading module.

[0046] As a further improvement of the technical solution, in S5.4, the particle swarm optimization algorithm is:

[0047] x j (t+1)=x j (t)+vx j (t+1);

[0048] y j (t+1)=y j (t)+vy j (t+1);

[0049] Among them, x j (t) represents the horizontal coordinate position of the shading module on the two-dimensional plane; y j (t) represents the ordinate position of the shading module on the two-dimensional plane; vx j (t+1) represents the velocity component of the shading module along the x direction at the next moment; vy j (t+1) represents the velocity component of the shading module along the y direction at the next moment; t represents the time variable.

[0050] As a further improvement of the technical solution, the signal demodulation unit demodulates the modulated signal detected by the detector to restore the information loaded by the Gaussian laser, including the following steps:

[0051] S6.1, converting the received optical signal into an electrical signal through a detector;

[0052] S6.2, use a bandpass filter to remove unwanted frequency components and shape the signal to have a clearer pulse shape;

[0053] S6.3, ensuring synchronization between the receiving end and the transmitting end by sending a synchronization signal;

[0054] S6.4, for the amplitude modulation ASK method, the original data is recovered by comparing the amplitude of the signal;

[0055] S6.5, performing digital signal processing on the demodulated signal;

[0056] S6.6. Use the bit error rate (BER) detection method to evaluate the quality of the demodulated signal and determine the number of error bits by comparing it with a reference signal. If bit errors occur during signal transmission, use error correction coding to correct the errors.

[0057] S6.7. Decode the demodulated signal to restore the original digital information.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] 1. The optical communication equipment for deep-sea underwater robots adopts laser communication technology, which meets the advantages of medium and long distance, high speed and miniaturization under the condition of low power consumption. The modulated Gaussian laser is converted into a non-diffraction beam by using a spatial light modulation unit, and the PID control algorithm is combined for alignment and directional emission. This optical communication equipment can maintain the good shape and intensity of the beam in the deep-sea underwater environment. This design effectively improves the stability of the communication link, reduces the signal attenuation and interference caused by the underwater environment, and thus ensures the reliability and accuracy of data transmission.

[0060] 2. In the optical communication equipment suitable for deep-sea underwater robots, the Gaussian beam emitted by the laser is modulated into a non-diffraction beam by combining a spatial light modulator and an optical noise reduction unit. The non-diffraction beam has a higher transmittance in water and can achieve longer-distance communication. At the same time, its self-focusing and self-healing properties provide a method for improving anti-interference and noise removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is the overall flow chart of the present invention;

[0062] Figure 2 It is the spatial light intensity distribution diagram of each order non-diffraction light beam-Bessel light beam of the present invention;

[0063] Figure 3 This is the spatial light intensity distribution diagram of the non-diffraction light beam-vortex light before and after denoising;

[0064] The meaning of each number in the figure is:

[0065] 1. Signal modulation unit; 2. Spatial light modulation unit; 3. Optical transmitting unit; 4. Optical receiving unit; 5. Optical noise reduction unit; 6. Signal demodulation unit. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0067] Example: See Figure 1 As shown, an optical communication device suitable for a deep-sea underwater robot is provided, comprising:

[0068] The signal modulation unit 1 loads the data signal to be transmitted onto the Gaussian laser generated by the laser, and loads the modulation signal onto the Gaussian laser;

[0069] Among them, the role of the laser is to generate a carrier of communication signals so that the signal can be loaded onto this carrier for transmission. Usually, the laser generated by the laser is a Gaussian beam;

[0070] In this embodiment, the signal modulation unit 1 loads the data signal to be transmitted onto the Gaussian laser generated by the laser, and loads the modulation signal onto the Gaussian laser, including the following steps:

[0071] S1.1. Prepare the data to be transmitted, which can be any form of data, such as text, images, videos, etc., and encode the data to convert it into a form suitable for transmission, usually binary code. This step also includes error detection and correction codes (such as FEC codes) to help the receiving end correct errors that may occur during the transmission process;

[0072] S1.2. Select the modulation mode as ASK modulation, and optimize the ASK modulation by considering the attenuation and absorption of the modulation signal;

[0073] Among them, ASK is one of the simplest modulation methods and is easy to implement because it only requires changing the amplitude of the carrier signal. Due to the simplicity of ASK, it is usually less expensive than other more complex modulation methods (such as PSK or QAM), especially in hardware implementation. The demodulation of ASK signals is relatively simple, and the data can be recovered by simply detecting the amplitude change of the signal, which reduces the complexity of the receiving end. Amplitude-shifted ASK modulation is:

[0074] s(t)=A(t)·cos(2πf c t+β);

[0075] In deep sea environment, light will be affected by absorption and scattering, resulting in weakened signal strength. By optimizing ASK modulation, this attenuation can be compensated to a certain extent, improving the detectability and reliability of the signal; by introducing the dynamic range adjustment factor, it can better adapt to the characteristics of the underwater channel, thereby improving the anti-interference ability of the signal, which means that even when the signal strength is weakened, it can maintain a high data transmission quality; by optimizing ASK modulation, the signal can maintain its original characteristics as much as possible during the transmission process, reduce the information loss caused by environmental factors, and thus improve the efficiency of data transmission; the optimization of ASK modulation can improve performance without increasing the complexity of the system, making the design of the entire communication system more concise and efficient; considering the problem of modulated signal attenuation and absorption, the amplitude keying ASK modulation is optimized as follows:

[0076] s1(t)=G(t)·A(t)·cos(2πf c t+β);

[0077] Where s(t) represents the modulated signal, that is, the signal value at time t; A(t) represents the amplitude function, which represents the instantaneous amplitude of the signal. It changes according to the data to be transmitted. If a digital signal is transmitted, "1" usually corresponds to a higher amplitude, and "0" corresponds to a lower amplitude or zero amplitude; f c represents the carrier frequency, that is, the center frequency of the unmodulated signal, which determines the frequency component of the signal; t represents the time variable; β represents the phase offset, which is a constant representing the initial phase of the carrier signal relative to a reference point; s1(t) represents the modulated signal considering the attenuation and absorption of the modulated signal; G(t) represents the dynamic range adjustment factor, which is used to compensate for the attenuation and absorption of the modulated signal during underwater propagation;

[0078] S1.3, using the selected modulation method, mapping the encoded data stream to the carrier signal;

[0079] S1.4. Load the modulated signal onto the Gaussian laser generated by the laser (use a driving circuit to control the current or voltage of the laser, thereby changing the characteristics of the laser (such as intensity, frequency or phase) so that it carries data information).

[0080] The spatial light modulation unit 2 converts the modulated Gaussian laser into a non-diffraction light beam, which has the ability of self-focusing and self-healing, can maintain a good shape and strength in water, and improves the anti-interference ability;

[0081] In this embodiment, the spatial light modulation unit is a spatial light modulator, which can modulate the Gaussian beam emitted by the laser into a non-diffraction beam. The non-diffraction beam has strong anti-interference performance and a higher transmittance in water than the Gaussian beam. The spatial light intensity distribution of each order of non-diffraction beam (Bessel beam) is as follows: Figure 2 As shown in the figure, the spatial light intensity distribution of each order of non-diffracting light beam (Bessel beam) is annular. The higher the order, the more obvious the characteristics of its phase singularity, and the larger the area of ​​the central zero light intensity.

[0082] The spatial light modulation unit 2 converts the modulated Gaussian laser into a non-diffraction light beam, including the following steps:

[0083] S2.1. Determine the order, wavelength and other parameters of the required non-diffraction beam;

[0084] S2.2, use the mathematical software MATLAB to calculate the corresponding phase distribution;

[0085] S2.3, generating a two-dimensional matrix hologram according to the calculated phase distribution;

[0086] Among them, each row and each column of this matrix represents the position of a pixel on the spatial light modulator (SLM), and each element value in the matrix represents the amount of phase delay that needs to be applied to the pixel at that position, and represents the phase delay that should be applied to each pixel point on the spatial light modulator SLM;

[0087] S2.4. Load the generated hologram onto the spatial light modulator SLM to ensure that each pixel on the spatial light modulator SLM can be modulated according to the phase delay indicated by the hologram.

[0088] The optical transmitting unit 3 uses a PID control algorithm to align and direct the emission of a non-diffraction light beam, ensuring that the light beam can be accurately transmitted to the receiving end;

[0089] In this embodiment, the optical transmitting unit includes a collimator and a galvanometer, which can collimate the emitted non-diffraction light beam and align the light beam to the signal receiving end; the laser, the signal modulation unit, the spatial light modulation unit and the optical transmitting unit constitute the signal transmitting end;

[0090] Among them, in an underwater environment, due to the influence of factors such as water flow and turbulence, the direction of the light beam is prone to deviation. The PID control algorithm can adjust the direction of the light beam in real time to ensure that the light beam is accurately aligned with the receiving end, thereby improving the reliability and stability of communication; PID control can provide dynamic tracking capabilities, and even if the position of the receiving end changes, the position of the transmitting end can be adjusted in time to maintain the alignment of the light beam; through continuous error correction, the PID control algorithm can ensure that the light beam always remains in a stable state during transmission, reducing signal loss or interruption caused by changes in the external environment; the optical transmitting unit 3 aligns and directs the emission of a diffraction-free light beam through the PID control algorithm, including the following steps:

[0091] S3.1. Set the parameters of the PID control algorithm (proportional coefficient P, integral coefficient I, differential coefficient D) and initialize the position of the transmitting unit;

[0092] S3.2, using sensors (such as photoelectric sensors, infrared sensors, etc.) installed around the optical transmitting unit 3 to detect whether the transmitting light beam is correctly aimed at the target;

[0093] S3.3, calculating the deviation between the actual position and the target position according to the signal strength fed back by the sensor;

[0094] S3.4. Calculate the control signal based on the current error through the PID control algorithm. The control signal consists of a proportional term (directly adjusted according to the error size), an integral term (accumulating historical errors to eliminate static errors) and a differential term (predicting the change trend of the error to reduce overshoot);

[0095] Furthermore, the control signal is calculated based on the current error through the PID control algorithm:

[0096]

[0097] Wherein, u(t) represents a control signal, that is, a command signal for adjusting the direction of the optical transmitting unit 3, such as the rotation angle or speed of the motor; K p Represents the proportional gain, which determines the degree of direct impact of the error on the output; K i Represents the integral gain, which is used to eliminate steady-state errors and adjust the output by integrating the accumulated error over time; K d represents the differential gain, which adjusts the output according to the rate of change of the error, helping to reduce overshoot and improve the response speed of the system; t represents the time variable; e(t) represents the difference between the actual direction of the current beam and the target direction; τ represents the integral variable, which takes values ​​from 0 to t during the integration process;

[0098] S3.5, transmitting the control signal output by the PID control algorithm to the optical transmitting unit 3, adjusting the angle and position of the transmitting unit;

[0099] S3.6, repeat steps S3.2 to S3.5 until the position of the optical emitting unit 3 reaches the expected target position and maintains a stable alignment state.

[0100] The optical receiving unit 4 collects the non-diffraction light beam transmitted from the optical transmitting unit 3 and performs preliminary focusing;

[0101] In this embodiment, the optical receiving unit receives and focuses the light signal received by the optical window, so that it passes through the optical noise reduction unit and is successfully detected by the detector;

[0102] The optical noise reduction unit 5 uses a filter module to remove scattered light of different wavelength bands, and uses a light shielding module to further eliminate noise in the vicinity of the phase singularity of the non-diffracted light beam;

[0103] In this embodiment, the optical noise reduction unit is a circular shading plate. The size of the circular shading plate is related to the type of non-diffracting light modulated by the spatial light modulator and its topological charge. The larger the topological charge, the larger the area of ​​the phase singularity, and the larger the area of ​​the shading plate. The stray light does not have the characteristic of phase singularity after passing through the optical focusing unit, so the stray light will gather near the phase singularity. The shading plate can reduce the influence of stray light on the signal light. The spatial light intensity distribution of the non-diffracting light beam (vortex light) before and after denoising is shown in the figure. Figure 3 As shown (the left figure shows the spatial light intensity distribution of the non-diffracting beam (vortex light) before denoising, and the right figure shows the spatial light intensity distribution of the non-diffracting beam (vortex light) after denoising), the non-diffracting beam (vortex light) in the figure has a ring-shaped distribution in the spatial light field. Before denoising, there is interference from stray light in the center. After passing through the denoising unit, the central stray light has been completely filtered out;

[0104] Wherein, using a filter module (filter) to remove scattered light of different wavelength bands includes the following steps:

[0105] S4.1. Measure the spectral characteristics of the optical signal, determine the main wavelength band of the signal and the wavelength band of the scattered light, record the data of the light intensity changing with the wavelength, analyze the data and mark the signal wavelength band to be retained and the scattered light wavelength band to be removed;

[0106] S4.2. Select the appropriate filter module type according to the results of spectral analysis, such as narrowband filter, long-wave pass filter, short-wave pass filter, etc., and determine the center wavelength, bandwidth, and transmittance of the filter module;

[0107] S4.3. Use optical simulation software to simulate the transmittance of the filter module to light of different wavelengths;

[0108] S4.4. Use the gradient descent method to optimize the design parameters of the filter module to achieve the best filtering effect.

[0109] Furthermore, a shading module (black shading plate) is used to further eliminate the noise in the vicinity of the phase singularity of the non-diffracting light beam, including the following steps:

[0110] S5.1. Use the numerical simulation software COMSOL Multiphysics to establish a propagation model of a non-diffraction beam, simulate the light field distribution, and identify the position of the phase singularity.

[0111] S5.2. Design the preliminary shape and size of the shading module according to the position of the phase singularity;

[0112] S5.3. Use genetic algorithm to optimize the shape and size of the shading module to ensure that it can accurately cover the phase singularity area, and use finite element analysis to verify whether the design of the shading plate can effectively reduce noise;

[0113] S5.4, using particle swarm optimization algorithm to adjust the position of the shading module;

[0114] Furthermore, in deep-sea underwater environments, there may be noise interference near the phase singularity of the non-diffracting light beam. The PSO algorithm can accurately find the optimal position of the shading module to ensure that the shading module can cover these phase singularity areas, thereby reducing the impact of noise on the signal; through the PSO algorithm, the position of the shading module can be dynamically adjusted to achieve the optimal shading effect. This method can find the global optimal solution in multiple dimensions, rather than the local optimal solution, thereby improving the shading efficiency of the shading module; the underwater environment may change continuously, such as water flow, temperature and other factors may cause the propagation characteristics of the light beam to change, the PSO algorithm can dynamically adjust the position of the shading module according to real-time data to adapt to these changes; the particle swarm optimization algorithm is:

[0115] x j (t+1)=x j (t)+vx j (t+1);

[0116] y j (t+1)=y j (t)+vy j (t+1);

[0117] Among them, x j (t) represents the horizontal coordinate position of the shading module on the two-dimensional plane; y j (t) represents the ordinate position of the shading module on the two-dimensional plane; vx j (t+1) represents the velocity component of the shading module along the x direction at the next moment; vy j(t+1) represents the velocity component of the shading module along the y direction at the next moment; t represents the time variable.

[0118] The signal demodulation unit 6 demodulates the modulated signal detected by the detector and restores the information loaded by the Gaussian laser;

[0119] In this embodiment, the signal demodulation unit can demodulate the signal loaded in the electrical signal detected by the detector, and the optical receiving unit, the optical noise reduction unit, the detector and the signal modulation unit constitute a signal receiving end;

[0120] The demodulation signal detected by the detector is demodulated to restore the information loaded by the Gaussian laser, including the following steps:

[0121] S6.1. The detector converts the received optical signal into an electrical signal, which is usually in the form of current or voltage. The detector can convert the received optical signal into an electrical signal and transmit it to the back-end circuit for demodulation;

[0122] S6.2, use a bandpass filter to remove unwanted frequency components, such as noise or DC components, and shape the signal to give it a clearer pulse shape for subsequent processing;

[0123] S6.3, ensuring synchronization between the receiving end and the transmitting end by sending a synchronization signal, which can be used to adjust the clock frequency of the receiving end to be consistent with that of the transmitting end;

[0124] S6.4, for the amplitude modulation ASK method, the original data is recovered by comparing the amplitude of the signal;

[0125] S6.5, performing digital signal processing on the demodulated signal, such as sampling, quantization and encoding;

[0126] S6.6. Use the bit error rate (BER) detection method to evaluate the quality of the demodulated signal and determine the number of error bits by comparing it with a reference signal. If bit errors occur during signal transmission, error correction coding (such as FEC) is used to correct the errors. Error correction coding requires adding redundant information at the transmitter and using this information to correct the errors at the receiver.

[0127] S6.7. Decode the demodulated signal to restore the original digital information.

[0128] In this embodiment, the working process of the optical communication equipment suitable for deep-sea underwater robots is specifically as follows: a modulated signal is loaded onto the Gaussian beam on the laser, where the modulation mode is not limited, and the modulated signal is transmitted to the spatial light modulator; the spatial light modulator converts the received Gaussian beam after the loaded signal into a non-diffraction beam, and the type and topological charge of the modulated non-diffraction beam are specified according to actual conditions. The larger the number of topological cores, the larger the area of ​​its phase singularity, that is, the larger the area of ​​the middle 0 light intensity point, which can make the filtering effect of the subsequent steps better. At the same time, the larger the number of topological cores, the higher the transmittance underwater and the longer the transmission distance; the non-diffraction beam passing through the spatial light modulator is transmitted to the optical transmitting unit, and the non-diffraction beam is smoothly transmitted to the signal receiving end through beam shaping, collimation and alignment of the galvanometer; the signal receiving end first focuses the signal after receiving it, and then passes the focused non-diffraction beam through the optical noise reduction unit; the non-diffraction light When the beam passes through the optical noise reduction unit, it first passes through the filter to filter out the stray light with band changes caused by scattering, and then passes through the non-diffraction light filter baffle. When passing through the filter baffle, the signal light forms a ring with an area larger than the filter baffle, so it is not blocked and passes smoothly; while the stray light does not have the properties of the vortex light phase singularity, it will be focused near the non-diffraction light beam phase singularity when passing through the focusing unit, and will be blocked by the baffle to achieve the effect of noise reduction. It should be noted that the size of the baffle is related to the type of non-diffraction light beam modulated by the spatial light modulator and the number of non-diffraction light beam topological cores. While ensuring the passage of the non-diffraction light beam, it is necessary to try to ensure that most of the stray light is filtered out; the low-noise non-diffraction light beam passing through the optical noise reduction unit passes through the detector, is converted into an electrical signal by the detector, and is demodulated by the demodulator to complete the underwater wireless laser communication with medium and long distance, high speed, low power consumption, high security and high anti-interference.

[0129] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. An optical communication device suitable for deep-sea underwater robots, characterized in that: include: A signal modulation unit (1), wherein the signal modulation unit (1) loads a data signal to be transmitted onto a Gaussian laser generated by a laser, and loads a modulation signal onto the Gaussian laser; A spatial light modulation unit (2), wherein the spatial light modulation unit (2) converts the modulated Gaussian laser into a non-diffraction light beam; An optical emitting unit (3), wherein the optical emitting unit (3) aligns and directs the emission of a non-diffraction light beam through a PID control algorithm; An optical receiving unit (4), wherein the optical receiving unit (4) collects the non-diffraction light beam transmitted from the optical transmitting unit (3) and performs preliminary focusing; An optical noise reduction unit (5), wherein the optical noise reduction unit (5) uses a filter module to remove scattered light of different wavelength bands, and uses a light shielding module to further eliminate noise in an area near a phase singularity of a non-diffracted light beam; A signal demodulation unit (6) is used to demodulate the modulation signal detected by the detector and restore the information loaded by the Gaussian laser.

2. The optical communication device suitable for deep-sea underwater robots according to claim 1, characterized in that: The signal modulation unit (1) loads the data signal to be transmitted onto the Gaussian laser generated by the laser, and loads the modulation signal onto the Gaussian laser, comprising the following steps: S1.

1. Prepare the data to be transmitted and encode the data; S1.

2. Select the modulation mode as ASK modulation, and optimize the ASK modulation by considering the attenuation and absorption of the modulation signal; S1.3, using the selected modulation method, mapping the encoded data stream to the carrier signal; S1.

4. Load the modulated signal onto the Gaussian laser generated by the laser.

3. The optical communication device suitable for deep-sea underwater robots according to claim 2, characterized in that: The S1.2, ASK modulation is: s(t)=A(t)·cos(2πf c t+β); Considering the attenuation and absorption of the modulation signal, the amplitude-shift keying (ASK) modulation is optimized as follows: s1(t)=G(t)·A(t)·cos(2πf c t+β); Where s(t) represents the modulated signal; A(t) represents the amplitude function; f c represents the carrier frequency; β represents the phase shift; s1(t) represents the modulated signal considering the attenuation and absorption of the modulated signal; G(t) represents the dynamic range adjustment factor, which is used to compensate for the attenuation and absorption of the modulated signal during underwater propagation.

4. The optical communication device suitable for deep-sea underwater robots according to claim 3, characterized in that: The spatial light modulation unit (2) converts the modulated Gaussian laser into a non-diffraction light beam, comprising the following steps: S2.

1. Determine the order, wavelength and other parameters of the required non-diffraction beam; S2.2, use the mathematical software MATLAB to calculate the corresponding phase distribution; S2.3, generating a two-dimensional matrix hologram according to the calculated phase distribution; S2.

4. Load the generated hologram onto the spatial light modulator SLM to ensure that each pixel on the spatial light modulator SLM can be modulated according to the phase delay indicated by the hologram.

5. The optical communication device suitable for deep-sea underwater robots according to claim 4, characterized in that: The optical emission unit (3) aligns and directs the emission of a non-diffraction light beam through a PID control algorithm, comprising the following steps: S3.1, set the parameters of the PID control algorithm and initialize the position of the transmitting unit; S3.2, using sensors installed around the optical transmitting unit (3) to detect whether the transmitting light beam is correctly aimed at the target; S3.3, calculating the deviation between the actual position and the target position according to the signal strength fed back by the sensor; S3.4, calculating the control signal based on the current error through the PID control algorithm; S3.5, transmitting the control signal output by the PID control algorithm to the optical transmitting unit (3), adjusting the angle and position of the transmitting unit; S3.6, repeat steps S3.2 to S3.5 until the position of the optical emitting unit (3) reaches the expected target position and maintains a stable alignment state.

6. The optical communication device suitable for deep-sea underwater robots according to claim 5, characterized in that: In S3.4, the control signal is calculated based on the current error by the PID control algorithm: Where, u(t) represents the control signal; K p Represents proportional gain; K i Indicates the integral gain; K d represents the differential gain; t represents the time variable; e(t) represents the difference between the actual pointing direction of the current beam and the target pointing direction; τ represents the integral variable.

7. The optical communication device suitable for deep-sea underwater robots according to claim 6, characterized in that: The optical noise reduction unit (5) uses a filter module to remove scattered light of different wavelength bands, comprising the following steps: S4.

1. Measure the spectral characteristics of the optical signal, determine the main wavelength band of the signal and the wavelength band of the scattered light, record the data of the light intensity changing with the wavelength, analyze the data and mark the signal wavelength band to be retained and the scattered light wavelength band to be removed; S4.

2. Select the appropriate filter module type according to the results of the spectrum analysis, and determine the center wavelength, bandwidth, and transmittance of the filter module; S4.

3. Use optical simulation software to simulate the transmittance of the filter module to light of different wavelengths; S4.

4. Use the gradient descent method to optimize the design parameters of the filter module.

8. The optical communication device suitable for deep-sea underwater robots according to claim 7, characterized in that: The method of further eliminating the noise in the vicinity of the phase singularity of the non-diffracting light beam by using the shading module comprises the following steps: S5.

1. Use the numerical simulation software COMSOL Multiphysics to establish a propagation model of a non-diffraction beam, simulate the light field distribution, and identify the position of the phase singularity. S5.

2. Design the preliminary shape and size of the shading module according to the position of the phase singularity; S5.

3. Use genetic algorithm to optimize the shape and size of the shading module to ensure that it can accurately cover the phase singularity area, and use finite element analysis to verify whether the design of the shading plate can effectively reduce noise; S5.

4. Use the particle swarm optimization algorithm to adjust the position of the shading module.

9. The optical communication device suitable for deep-sea underwater robots according to claim 8, characterized in that: In S5.4, the particle swarm optimization algorithm is: Among them, x j (t) represents the horizontal coordinate position of the shading module on the two-dimensional plane; y j (t) represents the ordinate position of the shading module on the two-dimensional plane; vx j (t+1) represents the velocity component of the shading module along the x direction at the next moment; vy j (t+1) represents the velocity component of the shading module along the y direction at the next moment; t represents the time variable.

10. The optical communication device suitable for deep-sea underwater robots according to claim 9, characterized in that: The signal demodulation unit (6) demodulates the modulated signal detected by the detector to restore the information loaded by the Gaussian laser, including the following steps: S6.1, converting the received optical signal into an electrical signal through a detector; S6.2, use a bandpass filter to remove unwanted frequency components and shape the signal to have a clearer pulse shape; S6.3, ensuring synchronization between the receiving end and the transmitting end by sending a synchronization signal; S6.4, for the amplitude modulation ASK method, the original data is recovered by comparing the amplitude of the signal; S6.5, performing digital signal processing on the demodulated signal; S6.

6. Use the bit error rate (BER) detection method to evaluate the quality of the demodulated signal and determine the number of error bits by comparing it with a reference signal. If bit errors occur during signal transmission, use error correction coding to correct the errors. S6.

7. Decode the demodulated signal to restore the original digital information.

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