Air-to-water cross-medium laser communication device based on linear-nonlinear mechanism

Abstract

The utility model discloses an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism, and belongs to the technical field of cross-medium communication. The device comprises a signal sending mechanism and a signal receiving mechanism, the signal sending mechanism is arranged on an aerial platform, the signal receiving mechanism is arranged in an underwater space, the signal sending mechanism comprises a first laser and a second laser, and the first laser and the second laser are both connected with a signal modulation module. The signal modulation module controls the two lasers to emit laser beams, the output ends of the two lasers are connected with the beam splitting equipment, the beam splitting equipment divides the light beams output by the lasers into two beams, the first beam is output and enters the energy monitoring module, and the second beam is vertically incident to a water-gas interface; the signal receiving mechanism comprises a signal processing module, a data acquisition device and a hydrophone, the speed, effectiveness and stability of air-to-water cross-medium communication are improved, and reliable and efficient underwater acoustic communication is realized.

Description

Technical Field

[0001] The present application belongs to the field of cross-medium communication technology, and more specifically, to an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism. Background Art

[0002] Cross-media communication is a key technology for integrated sea, air and space communication networking. Cross-media communication can break the boundaries between different communication media, realize direct communication between air platforms and underwater targets, and solve the problem of surface communication relay, thereby promoting seamless transmission and efficient interconnection of information. Cross-media communication technology provides a guarantee for the free flow of information between multiple fields such as the ocean, air and underwater, greatly improving the coverage, continuity and reliability of the communication network.

[0003] In the prior art, the laser-induced acoustic communication of the cross-media communication system mainly uses the synchronization sequence method to achieve code element synchronization. Before sending data, it is necessary to first send a synchronization sequence known to both communicating parties. The receiving party performs code element synchronization by detecting this sequence. The operation mode of the system requires the retrieval of the synchronization sequence. It takes a long time to establish clock synchronization, and occupies a certain amount of information bits, which reduces the communication rate and effectiveness. When there are errors in the transmission, clock synchronization cannot be established. Utility Model Content

[0004] The utility model aims at the technical problems existing in the prior art and provides an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism.

[0005] In order to solve the above technical problems, the utility model includes a signal sending mechanism and a signal receiving mechanism. The signal sending mechanism is arranged on an aerial platform, and the signal receiving mechanism is arranged in an underwater space. The signal sending mechanism includes a signal modulation module and a laser. The laser is connected to the signal modulation module. The signal modulation module obtains information to be sent, modulates the information to be sent and converts it into a laser control signal. The signal modulation module controls the laser to emit a laser beam. The laser includes a first laser and a second laser. The output ends of the two lasers are both connected to a beam splitting device. The beam splitting device divides the light beam output by the laser into two beams, wherein the first beam is output to enter an energy monitoring module, and the second beam is vertically incident on the water-air interface.

[0006] The signal receiving mechanism includes a signal processing module, a data acquisition device and a hydrophone. The laser acoustic signal generated by the signal sending mechanism on the water surface is transmitted through the hydroacoustic channel. After receiving the laser acoustic signal, the hydrophone converts the acoustic signal into an electrical signal, and the signal is collected through the data acquisition device. The collected signal is transmitted to the signal processing module.

[0007] Preferably, the light beam output by the laser is divided into two beams by a beam splitter, the first beam enters the energy monitoring module with 2% energy, and the second beam is vertically incident on the water-gas interface through an optical fiber, and the energy of the two lasers is controlled to produce thermal expansion and optical breakdown effects respectively, thereby converting the laser pulse signal into an acoustic signal;

[0008] When high-energy light is absorbed by water, a linear or nonlinear photoacoustic process will occur depending on the light irradiance and whether the properties of the water medium change. The thermal expansion mechanism is a linear mechanism, and the light breakdown mechanism is a nonlinear mechanism. The absorption of high light energy produces local temperature fluctuations in the water medium, thereby causing volume fluctuations, which will produce propagating acoustic signals.

[0009] Preferably, the signal receiving mechanism locates the laser-induced acoustic signal according to the position of the optical breakdown signal, divides the sampling signal, and retains the thermal expansion part. The signal receiving mechanism uses the first optical breakdown signal as the start code of the code element, the second optical breakdown signal as the end code of the code element, and the part between the two optical breakdown signals as the information code. The information code is stored, and the thermal expansion part is retained for decoding to obtain the transmitted information.

[0010] Preferably, the signal modulation module receives segmented binary sequence data, and generates two clock signals and two control signals according to the segmented binary sequence, and respectively controls two lasers to emit lasers. The two clock signals are completely synchronized, and the two control signals work in sequence.

[0011] Preferably, the signal sending mechanism also includes a laser rangefinder, which is connected to the signal modulation module. The laser rangefinder is arranged on the transmission route before the laser beam is incident on the water-gas interface after being split by the beam splitting device. The laser rangefinder includes a first laser rangefinder and a second laser rangefinder. The signal modulation module reads the distance data of the first laser rangefinder and the second laser rangefinder respectively, and then adjusts the target focal length of the first laser and the second laser as needed.

[0012] Preferably, the beam splitting device completes the energy distribution of laser energy separation and transmission and reflection energy detection; the beam splitting device includes a beam splitting plate, on which a beam splitter is arranged, the beam splitter includes a first beam splitter and a second beam splitter, the first beam splitter is connected to the first laser, the second beam splitter is connected to the second laser, and the first beam splitter and the second beam splitter are both 45° lenses.

[0013] Preferably, the data acquisition device comprises a data acquisition card, a first end of the data acquisition card is connected to the hydrophone, and a second end of the data acquisition card is connected to the signal processing module;

[0014] The hydrophone includes a fiber laser and a fiber sensor. An optical fiber with a periodic light field is formed in the hydrophone, which selectively feeds back light of a specific wavelength. The laser beam generates a frequency shift of light of a specific wavelength in the hydrophone.

[0015] Preferably, the signal receiving mechanism also includes a preamplifier.

[0016] Preferably, the signal modulation module includes a main control chip, a data storage module and a signal amplification module. The main control chip generates four control signals, which are amplified by the signal amplification module and then transmitted to the laser.

[0017] Preferably, the laser is a Nd:YGA focal length adjustable laser, and the hydrophone is a distributed feedback fiber laser hydrophone.

[0018] Compared with the prior art, the utility model has the following beneficial effects:

[0019] The utility model obtains the information to be transmitted through a signal sending mechanism, converts the information to be sent into a binary form, segments the data into a binary sequence of uniform length, and transmits the segmented binary sequence to a signal modulation module. The signal modulation module generates two clock signals and two control signals according to the segmented binary sequence, and respectively controls two lasers to emit laser beams. The light beam output by the laser is divided into two beams by a beam splitter, wherein a partial energy state of one beam enters an energy monitoring module so as to detect the energy of each laser pulse, and the other beam is vertically incident on the water-air interface through an optical fiber, and thermal expansion and optical breakdown effects are respectively generated by controlling the different energies of the two lasers, thereby converting the laser pulse signal into an acoustic signal that propagates in all directions underwater, and receiving the acoustic signal at any position underwater through a hydrophone, and demodulating the received signal to obtain the sending information, thereby completing the cross-medium communication from air to water. The utility model improves the speed, effectiveness and stability of the air-to-water cross-medium communication by utilizing an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism joint modulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 This is a schematic diagram of the structure of the cross-medium laser communication device of the utility model;

[0022] Figure 2This is a schematic diagram of the working process of the cross-medium laser communication device of the utility model.

[0023] Symbols in the figure:

[0024] 1. The first laser; 2. The second laser; 3. The signal modulation module; 4. The energy monitoring module; 5. The water-air interface; 6. The signal processing module; 7. The hydrophone; 8. The first spectroscope; 9. The second spectroscope; 10. The first laser rangefinder; 11. The second laser rangefinder; 12. The data acquisition card; 13. The preamplifier; 14. The optical fiber. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the following is a further detailed description of an air-to-water trans-medium laser communication device based on linear-nonlinear mechanism joint modulation provided by the present application in combination with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] See also Figure 1 The utility model provides an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism, comprising a signal sending mechanism and a signal receiving mechanism, wherein the signal sending mechanism is arranged on an aerial platform, and the signal receiving mechanism is arranged in an underwater space, the signal sending mechanism comprises a signal modulation module 3 and a laser, the laser is connected to the signal modulation module 3, the signal modulation module is used to obtain information to be sent, modulate the information to be sent and convert it into a laser control signal, the signal modulation module 3 controls the laser to emit a laser beam, the laser comprises a first laser 1 and a second laser 2, the output ends of the two lasers are both connected to a beam splitting device, the beam splitting device divides the light beam output by the laser into two beams, wherein the first beam is output and enters an energy monitoring module 4, and the second beam is vertically incident on a water-air interface 5; the signal receiving mechanism comprises a signal processing module 6, a data acquisition device and a hydrophone 7, the laser acoustic signal generated by the signal sending mechanism on the water surface is propagated through an underwater acoustic channel, the hydrophone 7 converts the acoustic signal into an electrical signal after receiving the laser acoustic signal, performs signal acquisition through the data acquisition device, and the acquired signal is transmitted to the signal processing module 6.

[0027] The utility model obtains the information to be transmitted through a signal sending mechanism, converts the information to be sent into a binary form, segments the data into a binary sequence of uniform length, and transmits the segmented binary sequence to a signal modulation module 3. The signal modulation module 3 generates two clock signals and two control signals according to the segmented binary sequence, and respectively controls two lasers to emit laser beams. The light beam output by the laser is divided into two beams by a beam splitter, wherein a partial energy state of one beam enters an energy monitoring module 4 so as to detect the energy of each laser pulse, and the other beam is vertically incident on a water-air interface 5 through an optical fiber 14. By controlling the different energies of the two lasers, thermal expansion and optical breakdown effects are respectively generated, and then the laser pulse signal is converted into an acoustic signal to propagate in all directions underwater. The acoustic signal is received at any position underwater by a hydrophone 7, and the received signal is demodulated to obtain the sending information, thereby completing the cross-medium communication from air to water. The utility model improves the speed, effectiveness and stability of air-to-water cross-medium communication by utilizing an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism joint modulation.

[0028] In this embodiment, the signal sending mechanism is a signal sending end, which is used to transmit and process signals, and the signal receiving mechanism is a signal receiving end, which is used to receive laser signals transmitted by the signal sending mechanism. The signal sending end and the signal receiving end are respectively arranged in the air and the water, so as to perform air-to-water cross-medium laser communication.

[0029] Specifically, the signal transmission mechanism includes two lasers with adjustable focal length, a beam splitter, an optical fiber 14, an energy monitoring module 4, a signal modulation module 3, and a laser rangefinder. The segmented binary sequence is transmitted to the signal modulation module 3, and the signal modulation module 3 generates two clock signals and two control signals according to the segmented binary sequence, respectively controlling the two lasers to emit lasers. The two lasers work together to transmit information by outputting laser beams. The beam splitter separates the laser energy, and the laser output beam is divided into two beams through the beam splitter, one of which enters the energy monitoring module 4 with 2% energy to detect the energy of each laser pulse; the other beam is vertically incident on the water-air interface 5 through the optical fiber, controlling the energy of the two lasers to produce thermal expansion and optical breakdown effects respectively, and then converting the laser pulse signal into an acoustic signal to propagate in all directions underwater.

[0030] In this embodiment, when high-energy light is absorbed by water, a linear or nonlinear photoacoustic process will occur depending on the light irradiance and whether the properties of the water medium change. The thermal expansion mechanism is a linear mechanism, and the light breakdown mechanism is a nonlinear mechanism. The absorption of high light energy produces local temperature fluctuations in the water medium, thereby causing volume fluctuations, and volume fluctuations will produce propagating sound signals.

[0031] Furthermore, in this embodiment, since the irradiance of light is jointly determined by the laser wavelength, output energy and spot size, and since the parameters of the laser are fixedly set and the laser rangefinder is operated to ensure that the focal length is always located at the water-gas interface, thereby ensuring that the spot size is basically constant, the two excitation states of the laser sound can be achieved by controlling the laser energy.

[0032] In this embodiment, the beam splitter device completes the energy separation of laser energy and the energy distribution of transmission and reflection energy detection. The beam splitter device includes a beam splitter plate, on which a beam splitter is arranged. The beam splitter includes a first beam splitter 8 and a second beam splitter 9. The first beam splitter 8 is connected to the first laser 1, and the second beam splitter 9 is connected to the second laser 2. Both the first beam splitter 8 and the second beam splitter 9 are 45° lenses. Since the beam splitter plate has a specific reflection and transmission ratio, the laser can be divided into two beams according to a predetermined ratio. By adjusting the characteristics of the beam splitter plate, 98% of the laser beam is transmitted and 2% of the laser beam is reflected for energy detection, thereby achieving the required energy distribution.

[0033] The signal modulation module 3 is the control module of the laser, which controls the two lasers to emit laser beams, and modulates the information to be sent and converts it into a laser control signal. The signal modulation module 3 includes a main control chip, a data storage module and a signal amplification module. The main control chip is STC12CA60S2. The main control chip generates four control signals, which are amplified by the signal amplification module and then transmitted to the laser.

[0034] The energy monitoring module 4 is used to detect the energy of each laser pulse, and the energy monitoring module may be a laser energy monitor.

[0035] Furthermore, the signal sending mechanism also includes a laser rangefinder, which is connected to the signal modulation module 3. The laser rangefinder is arranged on the transmission route before the laser beam is incident on the water-gas interface after being split by the beam splitting device. The laser rangefinder includes a first laser rangefinder 10 and a second laser rangefinder 11. The signal modulation module 3 reads the distance data of the first laser rangefinder 10 and the second laser rangefinder 11 respectively, and then adjusts the target focal length of the first laser 1 and the second laser 2 as needed.

[0036] This embodiment can measure the distance from the water surface by setting a laser rangefinder at the signal sending end. The laser is provided with an electric focusing device, and the laser focal length is adjusted by the electric focusing device to ensure that the focus is always located at the water-air interface, which is convenient for energy control. By adding laser rangefinders to the transmitting ends of the two lasers, the single-chip microcomputer of the main control chip periodically reads the distance data from the laser rangefinder, calculates the target focal length to which the spectroscope needs to be adjusted, and determines the direction and number of steps of lens movement based on the current lens position and the target focal length. During the lens adjustment process, the feedback information of the lens position is updated in real time for precise control.

[0037] Specifically, Figure 1 As shown, the signal receiving mechanism includes a signal processing module 6, a data acquisition card 12, a preamplifier 13 and a hydrophone 7. Data acquisition is performed through the data acquisition card 12. The first end of the data acquisition card 12 is connected to the hydrophone 7, and the second end of the data acquisition card 12 is connected to the signal processing module 6. The data acquisition card 12 transmits the electrical signal to the signal processing module 6. The hydrophone 7 includes a fiber laser and a fiber sensor. The laser acoustic signal generated by the laser on the water surface is propagated through the hydroacoustic channel. The hydrophone 7 receives the laser acoustic signal generated by the laser on the water surface and converts the acoustic signal into an electrical signal. Signal acquisition is performed through the data acquisition card 12, and the acquired signal is transmitted to the signal processing module 6. The hydrophone 7 processes and receives the hydroacoustic signal to obtain the frequency and phase information of the hydroacoustic signal, thereby realizing the detection and measurement of the hydroacoustic signal.

[0038] In this embodiment, when the laser beam emitted by the fiber laser passes through a periodic feedback grating structure, only light of a specific wavelength can be fed back, thereby forming an optical fiber with a periodic light field. The light field is called a fiber grating, and the fiber grating can play a role in selectively feeding back light of a specific wavelength. In a distributed feedback fiber laser hydrophone, the laser beam first passes through a polarizer so that only light of a specific polarization direction is excited in the optical fiber. Then, this laser beam of a specific polarization direction is input into the feedback grating region in a long optical fiber. When the hydroacoustic signal acts near the optical fiber sensor, the hydroacoustic signal will cause a slight change in the length of the optical fiber. This length change is reflected in the fiber grating, causing a slight change in the period of the fiber grating. This period change will change the phase of the specific wavelength light fed back, thereby generating a frequency shift of the specific wavelength light. By measuring the change in the optical frequency, the frequency and phase information of the hydroacoustic signal can be obtained, thereby realizing the detection and measurement of the hydroacoustic signal.

[0039] As a preferred embodiment of the present application, the laser used in the present application is a Nd:YGA focal length adjustable laser, and the hydrophone 7 is a distributed feedback fiber laser hydrophone, specifically a DFB-FL high frequency hydrophone.

[0040] In this embodiment, the signal modulation module 3 receives the binary sequence data after segmentation. The signal modulation module 3 generates two clock signals and two control signals according to the binary sequence after segmentation, and controls the first laser 1 and the second laser 2 to emit lasers respectively. The two clock signals are completely synchronized, thereby ensuring the accuracy of the code element, and the two control signals work in sequence. At the starting position and the end position of the code element, the first control signal controls the first laser 1 to generate a light breakdown signal as the code element start code and the end code, and in the middle part of the code element, the second control signal controls the second laser 2 to generate a thermal expansion signal to transmit information. The working process of the control module mainly depends on the main control chip. The main control chip generates four control signals, which are amplified by the signal amplification module, and then the amplified signals are transmitted to the laser. The laser adopts the TTL level standard, that is, the logic high level is defined as +5V, and the logic low level is between 0V and +0.8V. The amplification module should ensure that the voltage is stable and meets the TTL level standard.

[0041] In this embodiment, since the amplitude of the optical breakdown signal is much higher than the amplitude of the thermal expansion signal, rapid positioning can be achieved in the sampled signal. The optical breakdown signal generated by the first laser 1 is a start code and a stop code, and the thermal expansion signal part generated by the second laser 2 between the two optical breakdown signals is an information code. The information code is stored and the rest is discarded, which can reduce the amount of calculation. Then, the information code is stored, and the thermal expansion part is retained by decoding to obtain the sent information.

[0042] The present application utilizes a light breakdown mechanism as the start code and end code of a code element. Since the amplitude of the light breakdown mechanism is significantly higher than that of the thermal expansion mechanism, the code element position can be quickly located in the received signal and clock synchronization can be achieved, thereby avoiding the problem of long synchronization time caused by retrieving a synchronization sequence. The number of bits occupied is significantly lower than that of the synchronization sequence, thereby improving effectiveness and making the laser communication between the aerial platform and the underwater target more reliable and efficient. This solves the problem of long synchronization time and large amount of calculation in the prior art which mainly utilizes the thermal expansion mechanism and adopts a synchronization sequence to perform clock synchronization.

[0043] Figure 2 The schematic diagram of the working process of the cross-medium laser communication device of the utility model includes the following steps:

[0044] Acquire information to be sent, segment the information to be sent, and segment the data into binary sequences;

[0045] The segmented binary sequence is transmitted to the signal modulation module. The signal modulation module 3 generates two clock signals and two control signals according to the segmented binary sequence to control the two lasers to emit laser beams respectively.

[0046] The beam output by the laser is divided into two beams by the beam splitter. The first beam enters the laser energy monitor at 2% energy state, and the second beam is vertically incident on the water-air interface 5 through the optical fiber 14. The energy of the two lasers is controlled to produce thermal expansion and optical breakdown effects respectively, and the laser pulse signal is converted into an acoustic signal to propagate in all directions underwater.

[0047] The hydrophone 7 receives the laser acoustic signal generated by the laser on the water surface, converts the acoustic signal into an electrical signal, and transmits the collected signal to the signal processing module 6;

[0048] The laser-induced acoustic signal is located according to the position of the optical breakdown signal, and the sampled signal is divided, retaining the thermal expansion part;

[0049] The retained thermal expansion part is decoded to obtain the transmitted information and complete the cross-media communication.

[0050] The utility model obtains the information to be transmitted through a signal sending mechanism, converts the information to be sent into a binary form, segments the data into a binary sequence of uniform length, and transmits the segmented binary sequence to a signal modulation module. The signal modulation module generates two clock signals and two control signals according to the segmented binary sequence, and respectively controls two lasers to emit laser beams. The light beam output by the laser is divided into two beams by a beam splitter, wherein a partial energy state of one beam enters a laser energy monitor so as to detect the energy of each laser pulse, and the other beam is vertically incident on the water-air interface through an optical fiber, and thermal expansion and optical breakdown effects are respectively generated by controlling the different energies of the two lasers, thereby converting the laser pulse signal into an acoustic signal that propagates in all directions underwater, and receiving the acoustic signal at any position underwater through a hydrophone, and demodulating the received signal to obtain the sending information, thereby completing the cross-medium communication from air to water. The utility model improves the speed, effectiveness and stability of the air-to-water cross-medium communication by utilizing an air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism joint modulation.

[0051] In the description of the present invention, it should be understood that terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0052] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0053] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism, comprising a signal sending mechanism and a signal receiving mechanism, wherein the signal sending mechanism is arranged on an aerial platform, and the signal receiving mechanism is arranged in an underwater space, characterized in that: The signal sending mechanism includes a signal modulation module and a laser, the laser is connected to the signal modulation module, the signal modulation module obtains information to be sent, modulates the information to be sent and converts it into a laser control signal, the signal modulation module controls the laser to emit a laser beam, the laser includes a first laser and a second laser, the output ends of the two lasers are connected to a beam splitting device, the beam splitting device splits the light beam output by the laser into two beams, wherein the first beam is output to enter the energy monitoring module, and the second beam is vertically incident on the water-gas interface; The signal receiving mechanism includes a signal processing module, a data acquisition device and a hydrophone. The laser acoustic signal generated by the signal sending mechanism on the water surface is propagated through the hydroacoustic channel. After receiving the laser acoustic signal, the hydrophone converts the acoustic signal into an electrical signal, and performs signal acquisition through the data acquisition device, and the acquired signal is transmitted to the signal processing module.

2. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The light beam output by the laser is divided into two beams by a beam splitter. The first beam enters the energy monitoring module with 2% of the energy, and the second beam is vertically incident on the water-gas interface through an optical fiber. The energy of the two lasers is controlled to produce thermal expansion and optical breakdown effects respectively, thereby converting the laser pulse signal into an acoustic signal.

3. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 2, characterized in that: The signal receiving mechanism locates the laser-induced acoustic signal according to the position of the optical breakdown signal, divides the sampling signal, and retains the thermal expansion part. The signal receiving mechanism uses the first optical breakdown signal as the start code of the code element, the second optical breakdown signal as the end code of the code element, and the part between the two optical breakdown signals as the information code.

4. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The signal modulation module receives segmented binary sequence data, and generates two clock signals and two control signals according to the segmented binary sequence, and controls two lasers to emit lasers respectively.

5. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The signal sending mechanism also includes a laser rangefinder, which is connected to the signal modulation module. The laser rangefinder is arranged on the transmission route before the laser beam is incident on the water-gas interface after being split by the beam splitting device. The laser rangefinder includes a first laser rangefinder and a second laser rangefinder. The signal modulation module reads the distance data of the first laser rangefinder and the second laser rangefinder respectively, and then adjusts the target focal length of the first laser and the second laser as needed.

6. The air-to-water cross-medium laser communication device based on a linear-nonlinear mechanism according to any one of claims 1-5, characterized in that: The beam splitting device completes the energy distribution of laser energy separation and transmission and reflection energy detection; the beam splitting device includes a beam splitting plate, a beam splitter is arranged on the beam splitting plate, and the beam splitter includes a first beam splitter and a second beam splitter, the first beam splitter is connected to the first laser, the second beam splitter is connected to the second laser, and the first beam splitter and the second beam splitter are both 45° lenses.

7. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The data acquisition device comprises a data acquisition card, a first end of the data acquisition card is connected to the hydrophone, and a second end of the data acquisition card is connected to the signal processing module; The hydrophone comprises a fiber laser and a fiber sensor. An optical fiber with a periodic light field is formed in the hydrophone, which selectively feeds back light of a specific wavelength. The laser beam generates a frequency shift of the light of the specific wavelength in the hydrophone.

8. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The signal receiving mechanism also includes a preamplifier.

9. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The signal modulation module includes a main control chip, a data storage module and a signal amplification module. The main control chip generates four control signals, which are amplified by the signal amplification module and then transmitted to the laser.

10. The air-to-water trans-medium laser communication device based on a linear-nonlinear mechanism according to claim 1, characterized in that: The laser is a Nd:YGA focal length adjustable laser, and the hydrophone is a distributed feedback fiber laser hydrophone.

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