A method and system for measuring the vertical profile temperature of a body of water

Abstract

The present application relates to a kind of water body vertical profile temperature measurement method and system, belong to water body temperature field detection technical field.The method includes: obtaining the optical fiber phase change signal of multiple optical fiber channels, according to each the optical fiber phase change signal obtains multiple acoustic receiving signals;Each the acoustic emission signal corresponding to the acoustic receiving signal is obtained, according to each the acoustic emission signal and each the acoustic receiving signal obtains multiple propagation times, according to each the propagation time obtains water body vertical profile sound speed;According to the water body vertical profile sound speed, water body vertical profile temperature is calculated.This application is by using the principle that optical fiber phase change signal is influenced by acoustic signal and changes, causes the change of optical fiber phase change signal, uses optical fiber as the receiving equipment of acoustic signal, instead of originally high cost and difficult to install acoustic equipment, realizes the detection of water body temperature large range high accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water body temperature field detection, and in particular to a water body vertical profile temperature measurement method and system. BACKGROUND

[0002] Seawater temperature, salinity and depth are three important parameters of basic hydrological information of the ocean. In the development and utilization of marine resources, accurate mastery of these parameters is crucial for accelerating the research of marine development technology and promoting the development of China's marine development.

[0003] At present, local high-resolution water temperature is obtained by fixed-point or underway measurement technology such as Conductivity Temperature Depth (CTD). Although fixed-point or underway measurement technology such as CTD can obtain local water temperature data, it cannot realize high-resolution real-time monitoring of temperature in a large range of water.

[0004] Acoustic tomography technology has a wide range of applications in many fields. As a technology that reconstructs the internal structure of an object by measuring the path and time of sound waves propagating inside the object. In temperature field reconstruction, this technology measures the change of sound wave propagation speed at different temperatures, and then calculates the temperature distribution inside the object. This technology is non-contact and does not interfere with the measured temperature field, and has the advantages of wide temperature measurement range, strong environmental adaptability, and suitability for large-scale space.

[0005] Based on this evolution of acoustic tomography water temperature field detection technology, by emitting acoustic signals and receiving the time difference of their propagation in different water layers, the correspondence between the sound speed field and the temperature field, density field is established. When the sound wave passes through water masses with different physical properties, its propagation path and time delay will produce quantifiable changes. Through the phase difference of multi-point received signals, three-dimensional space reconstruction is carried out, and then the distribution characteristics of temperature, salinity and other parameters are deduced. Therefore, acoustic tomography water temperature field detection technology can be used for large-scale water temperature monitoring, and can monitor the temperature field and flow field of millions of square kilometers of sea area.

[0006] However, the traditional acoustic tomography water temperature field detection technology has the following limitations and challenges in temperature field reconstruction: 1. Precision problem: due to the complexity of water sound wave propagation and the influence of external interference, it is difficult to achieve high-precision water temperature field reconstruction.

[0007] 2. Speed problem, the traditional acoustic tomography method needs a long calculation time when processing a large amount of data, which cannot meet the real-time or near real-time demand.

[0008] And the existing acoustic tomography water temperature field detection technology is based on the old equipment with integrated receiving and transmitting, which is complex to install, high in installation cost and unable to be laid in detail, so that the acoustic tomography water temperature field detection technology based on the equipment is difficult to be applied in meter-level high-resolution temperature inversion and small-area (water vertical section) monitoring.

[0009] Therefore, the prior art lacks a large-scale high-precision water temperature field detection technology to compensate for the inaccuracy of measurement results caused by measurement noise equipment drift and other problems in engineering practice, and to lay a foundation for high-precision water temperature inversion. SUMMARY

[0010] The purpose of the present application is to provide a water vertical section temperature measurement method and system, which aims to solve the problem that the prior art is limited by acoustic measurement equipment and cannot perform large-scale high-precision water temperature detection.

[0011] The technical solution adopted by the present application to solve the technical problems is as follows:

[0012] The present application provides a water vertical section temperature measurement method, comprising the following steps:

[0013] Obtaining optical fiber phase change signals of multiple optical fiber channels, and obtaining multiple acoustic receiving signals according to the optical fiber phase change signals;

[0014] Obtaining acoustic emission signals corresponding to each acoustic receiving signal, obtaining multiple propagation times according to each acoustic emission signal and each acoustic receiving signal, and obtaining water vertical section sound velocity according to each propagation time;

[0015] The water vertical section temperature is calculated according to the water vertical section sound velocity.

[0016] In one embodiment, the optical fiber phase change signals of multiple optical fiber channels are obtained, comprising:

[0017] A distributed optical fiber acoustic wave sensing system containing a host, a switching cable and a sensitized submarine cable is deployed and settled to the bottom of the water as an acoustic signal receiving end, wherein the sensitized submarine cable adopts a spiral structure communication submarine cable;

[0018] A ship-borne active sound source emits a linear frequency modulation signal around the sensitized submarine cable, and records the positioning information of the sound source through differential GPS;

[0019] The distributed optical fiber acoustic wave sensing system collects optical fiber phase change signals of multiple optical fiber channels on the sensitized submarine cable in real time.

[0020] The sensitivity of signal receiving can be improved by replacing the ordinary communication cable with a sensitive cable with a spiral structure and sinking the cable to the bottom of the water as a sound signal receiving end by its own gravity. The optical fiber used in the distributed acoustic sensing system (DAS) can be pre-laid in the target area, even using the existing optical fiber communication network, without the need for additional installation of complex acoustic receiving equipment, which greatly reduces the deployment difficulty and cost of the transceiver system. In addition, the DAS technology can realize distributed acoustic signal receiving along the length of the optical fiber at a meter level or even higher interval, thereby significantly increasing the number of sound propagation paths, improving the situation where the number of paths is limited, and improving the spatial resolution of temperature inversion.

[0021] In one embodiment, the obtaining of the plurality of acoustic receiving signals according to the respective optical fiber phase change signals comprises:

[0022] For each of the optical fiber phase change signals, the length change of the optical fiber caused by the disturbance of the acoustic wave is calculated according to the optical fiber phase change signal: wherein, represents the demodulation phase of the optical fiber phase change signal at time, represents the refractive index of the optical fiber, represents the wavelength of the laser, represents the length change of the optical fiber caused by the disturbance of the acoustic wave at

[0023] The axial strain of the optical fiber is calculated according to the length change The axial strain of the optical fiber is calculated according to the length change The axial strain of the optical fiber is calculated according to the length change : ;

[0024] The axial strain of the optical fiber is calculated according to the length change The axial strain of the optical fiber is calculated according to the length change

[0025] In one embodiment, the obtaining of the plurality of acoustic receiving signals according to the respective optical fiber phase change signals comprises:

[0026] For each optical fiber channel, the peak delay time is obtained according to the acoustic receiving signal and the corresponding acoustic transmitting signal;

[0027] For each optical fiber channel, the peak delay time of a set number of adjacent optical fiber channels is obtained, and the peak delay time of the optical fiber channel and the average delay time of the peak delay time of each of the adjacent optical fiber channels are calculated;

[0028] For each optical fiber channel, the corresponding average delay time is taken as the propagation time.

[0029] In one embodiment, the peak delay time of the fiber channel comprises:

[0030] For each fiber channel, the correlation degree of each delay time is obtained by matching filtering the acoustic receiving signal with the acoustic transmitting signal, and is calculated as follows:

[0031]

[0032] wherein, is the correlation degree of the acoustic receiving signal and the acoustic transmitting signal when the delay time is represents the acoustic receiving signal at time represents the complex conjugate of the acoustic transmitting signal at time

[0033] The delay with the highest correlation degree between each delay is taken as the peak delay time.

[0034] In one embodiment, the vertical profile sound speed of the water body is obtained according to each propagation time, comprising:

[0035] The vertical profile of the water body is divided into a plurality of grids;

[0036] The slowness of each grid is calculated according to each propagation time:

[0037]

[0038] wherein, represents a vector composed of the slowness of each grid, represents a vector composed of each propagation time, represents a transpose, represents an error matrix, is an error coefficient, represents a matrix describing the relationship between the propagation time and the slowness;

[0039] For each grid, the inverse of the slowness is calculated to obtain the sound speed of the grid;

[0040] The combination of the sound speed of each grid is taken as the vertical profile sound speed of the water body.

[0041] In one embodiment, the vertical profile temperature of the water body is calculated according to the vertical profile sound speed of the water body, comprising:

[0042] The salinity and depth of each grid are obtained, and for each grid, the temperature of the grid is calculated according to the salinity, the depth and the sound speed;

[0043] ​​​​​The combination of the temperatures of each of the grids is taken as the vertical profile temperature of the water body.

[0044] In one embodiment, before obtaining the sound velocity in the vertical profile of the water body based on each of the propagation times, the method further includes:

[0045] Based on the average delay time, the distance between each acoustic receiving location and the sound source is calculated by solving the distance equation between each optical fiber channel and multiple sound sources.

[0046] Based on the distance equation and combined with the propagation time, the position of each fiber channel is corrected using the hypersurface intersection method or Gauss-Markov estimator.

[0047] In one embodiment, the hypersurface intersection method includes: locating the three-dimensional coordinates of the fiber optic channel by solving the distance equation, as follows:

[0048] ,

[0049] ,

[0050] in, Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates the first One sound source Axis coordinates Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates the relationship with the first The distance between the sound sources Indicates the speed of sound in the propagation medium. Indicates the fiber channel to the first The average delay time of each sound source;

[0051] The Gauss-Markov estimator includes:

[0052] The Gauss-Markov estimator was used to jointly invert the location of the sound source, the location of the fiber optic channel, and the sound velocity.

[0053] Optimize the location of the sound source and the fiber optic channel based on the spacing constraints of the enhanced submarine cable design;

[0054] The three-dimensional shape of the optical fiber in the enhanced submarine cable is reconstructed by interpolation.

[0055] In addition, to achieve the above object, the application further provides a water vertical section temperature measuring system, comprising:

[0056] An acoustic conversion module is configured to acquire fiber phase change signals of multiple fiber channels, and acquire multiple acoustic receiving signals according to the fiber phase change signals.

[0057] A sound velocity calculation module is configured to acquire acoustic emission signals corresponding to the acoustic receiving signals, acquire multiple propagation times according to the acoustic emission signals and the acoustic receiving signals, and acquire a water vertical section sound velocity according to the propagation times.

[0058] A temperature calculation module is configured to calculate a water vertical section temperature according to the water vertical section sound velocity.

[0059] The application has the following effects by using the above technical solutions:

[0060] The application uses optical fibers as acoustic signal receiving devices to replace the originally high-cost and difficult-to-install acoustic devices, and realizes large-range and high-precision detection of water temperature by using the principle that the fiber phase change signals are deformed and changed by acoustic signals. BRIEF DESCRIPTION OF DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced.

[0062] Figure 1 is a step flow chart of the water vertical section temperature measuring method provided in the preferred embodiment of the application.

[0063] Figure 2 is a structural schematic diagram of the high-sensitivity distributed optical fiber acoustic wave sensing system provided in the preferred embodiment of the application.

[0064] Figure 3 is a division schematic diagram of the water vertical section provided in the preferred embodiment of the application.

[0065] Figure 4 is a structural schematic diagram of the water vertical section temperature measuring provided in the preferred embodiment of the application. DETAILED DESCRIPTION

[0066] In order to make the objects, technical solutions and advantages of the application more clearly understood, the following will combine the drawings and specific embodiments to further describe the application.

[0067] The embodiments are further described in detail. It should be understood that the specific embodiments described herein are only used to explain the application, and do not limit the protection scope of the application.

[0068] Referring to Figure 1 and Figure 2 , the embodiment provides a water body vertical profile temperature measurement method, which comprises the following steps:

[0069] S1, obtaining the optical fiber phase change signals of a plurality of optical fiber channels, and obtaining a plurality of acoustic receiving signals according to each of the optical fiber phase change signals.

[0070] Specifically, referring to Figure 2 , in the embodiment, the acoustic signal is obtained based on the high-sensitivity distributed acoustic sensing (DAS) technology, and the DAS system is composed of a DAS host, a conversion cable and a sensitized submarine cable. In order to improve the signal receiving sensitivity, the spiral sensitized submarine cable is used instead of the ordinary communication submarine cable, and the submarine cable is settled to the bottom of the water by its own gravity, which is used as the underwater acoustic signal receiving end.

[0071] The optical fiber used by the DAS can be pre-laid in the target area, or even use the existing optical fiber communication network, without the need to install complex acoustic receiving equipment additionally, which greatly reduces the deployment difficulty and cost of the transceiver system. In addition, the DAS technology can realize distributed acoustic signal receiving along the length of the optical fiber at a meter level or even higher interval, thereby significantly increasing the number of acoustic propagation paths, improving the situation of limited path number, and improving the spatial resolution of temperature inversion.

[0072] In the embodiment, first, the shipborne active sound source equipment is used to emit a linear frequency modulation signal at the point around the sensitized submarine cable, and the high-precision positioning information of the sound source is obtained by using the differential GPS (Global Positioning System).

[0073] The mathematical expression of the linear frequency modulation (LFM) signal is:

[0074] ,

[0075] Among them, represents the linear frequency modulation signal at the moment t, represents the signal amplitude of the linear frequency modulation signal, represents the starting frequency of the linear frequency modulation signal, represents the modulation frequency of the linear frequency modulation signal, and specifically the modulation frequency is:

[0076] ,

[0077] ​wherein, denotes the terminal frequency of the chirp signal, denotes the signal duration of the chirp signal.

[0078] Then, according to the DAS phase demodulation principle, the axial strain of each optical fiber channel is converted into the received acoustic pressure and velocity signals to obtain the underwater acoustic propagation information.

[0079] Specifically, the phase demodulation formula of the DAS is:

[0080] ,

[0081] wherein, denotes the demodulation phase at the moment, denotes the optical fiber refractive index, denotes the laser wavelength, denotes the length change of the optical fiber caused by the acoustic wave disturbance at the moment, It can be seen that as the optical fiber is disturbed by the acoustic wave, the demodulation phase of the DAS will also change accordingly, therefore, based on the demodulation phase of the DAS, the length change of the optical fiber caused by the acoustic wave disturbance can be restored, and further the acoustic pressure signal and the velocity signal of the acoustic wave can be restored. Specifically, according to the length change

[0082] the axial strain of the optical fiber is calculated , and then the axial strain is converted into the velocity :

[0083] ,

[0084] The acoustic pressure and the velocity present a proportional relationship:

[0085] ,

[0086] wherein, denotes the density of the propagation medium, denotes the acoustic velocity, therefore, knowing the velocity clears the change relationship between the acoustic pressures at different moments, therefore, the velocity can be taken as the acoustic receiving signal.

[0087] Thus, through the restoration of the velocity , the DAS can restore the axial strain of the sensitized submarine cable according to the obtained signal, and further restore the acoustic receiving signal propagated to the sensitized submarine cable.

[0088] S2, acquiring an acoustic emission signal corresponding to each of the acoustic reception signals, acquiring a plurality of propagation times according to each of the acoustic emission signals and each of the acoustic reception signals, and acquiring a vertical profile sound speed of the water body according to each of the propagation times.

[0089] After that, the acquired acoustic reception signal of the underwater acoustic propagation information needs to be cross-correlated with the acoustic emission signal. Specifically, the acoustic reception signal received by the DAS is matched filtered with the acoustic emission signal of the sound source to generate a compressed pulse. The compressed pulse helps to improve the signal-to-noise ratio (SNR). Due to the poor consistency of the DAS channels, in order to improve the collection accuracy and accuracy of the acoustic signal, 21 adjacent channels (10 channels on the left and right of the target channel) are used for delay summation. A peak automatic search algorithm is used to extract the propagation time of each channel, that is, to extract the accurate delay time from the mixed multi-source signal.

[0090] Specifically, for each channel, the acoustic reception signal is matched filtered with the acoustic emission signal, and the output signal of the matched filtering is:

[0091] ,

[0092] Wherein, is the output signal, and the delay is Under the condition that the acoustic reception signal is matched with the acoustic emission signal, represents the acoustic reception signal at time represents the complex conjugate of the acoustic emission signal at time .

[0093] After that, for each channel, the peak delay time is extracted, wherein for the first channel, the peak delay time is obtained, a superscript is added to distinguish the delay time between receiving it and different sound sources, and then the peak delay times of the 21 channels are averaged to obtain the average delay time of each acoustic emission signal and the corresponding acoustic reception signal:

[0094] ,

[0095] Wherein, represents the average delay time of the acoustic emission signal of the first sound source, represents the number of channels, represents the peak delay time of the acoustic emission signal of the first channel and the first sound source, and in the embodiment ​The value is 21. Through averaging, spatial averaging can suppress random errors, making the correlation peak positions more statistically stable and providing reliable input for sound velocity inversion. Multi-channel processing overcomes the channel inconsistency defects of the DAS system, improving the resolution of temperature field inversion.

[0096] Then, based on the average delay time between each received acoustic signal and the transmitted acoustic signal, the distance between each receiving location and the sound source is calculated, thereby locating each sound source:

[0097] ,

[0098] in, Indicates the relationship with the first The distance between the sound sources It represents the speed of sound in the propagation medium.

[0099] By solving the distance equations between each fiber optic channel and multiple sound sources, and combining this with the hypersurface intersection method, the three-dimensional coordinates of the fiber optic channels are obtained:

[0100] ,

[0101] in, Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates the first One sound source Axis coordinates Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates.

[0102] In this embodiment, in addition to using the hypersurface intersection method to obtain the three-dimensional coordinates of the optical fiber channel, a Gauss-Markov estimator can also be used to perform joint inversion solving based on the design spacing of the enhanced submarine cable, thereby optimizing the cable position, source position, and signal propagation speed.

[0103] After locating each fiber optic channel, the three-dimensional shape of the sensitized submarine cable can be reconstructed by smoothing the fiber using interpolation methods (such as spline interpolation) based on its accurate position. Dynamic position correction via acoustic propagation time effectively solves the problem of underwater acoustic velocity tomography errors caused by the actual deployment location of the fiber being shifted due to water flow and gravity.

[0104] In this embodiment, after the three-dimensional shape positioning of the optical fiber of the sensitized submarine cable is completed, a transceiver asynchronous mode is used, that is, the acoustic emission signal of the underwater acoustic transmitter, and the DAS system only acoustically receives the signal. M transmitters sequentially emit different modal signals of the same order as the acoustic emission signal. In this embodiment, the duration of each signal is set to 3-8 seconds, and the transmitters are emitted in turn. A plurality of optical fiber channels are selected as underwater acoustic receiving units, and each underwater acoustic receiving unit records the corresponding acoustic receiving signal.

[0105] Please refer to Figure 3 , and then for each underwater acoustic receiving unit, the acoustic receiving signal and the acoustic emission signal are matched filtered to generate compressed pulses and extract the average delay time to obtain the propagation time . If M sound sources and N receivers are set, M*N sound rays will be generated, and M*N propagation times will be generated. In this embodiment, 3 sound sources and 7 receivers are specifically set, and a total of 21 sound rays are generated, and 21 propagation times are also generated: .

[0106] Among them, represents the transpose, represents a vector composed of the propagation times of each sound ray, represents the propagation time of the first sound ray, represents the propagation time of the second sound ray, represents the propagation time of the third sound ray, represents the propagation time of the fourth sound ray, represents the propagation time of the fifth sound ray, represents the propagation time of the 21st sound ray.

[0107] The vertical profile of the water body is divided into a plurality of square grids, and it is assumed that the sound speed of each grid is the same. The transmission time of the sound wave through each grid is proportional to the length of the grid. By measuring the transmission time of the sound through different grids, the sound speed of each grid can be calculated.

[0108] In this embodiment, the vertical profile of the water body is divided into 36 grids, and the length and width of each grid are , the slowness of each grid is defined as the reciprocal of the sound speed, and the slowness of the 36 grids is , wherein represents a vector composed of the slowness of each grid, represents the slowness of the first grid, represents the slowness of the second grid, represents the slowness of the third grid, represents the slowness of the fourth grid, represents the slowness of the fifth grid, The slowness of the 36th grid.

[0109] After that, the solution is solved with the target of , wherein is the error coefficient, is the error matrix, is the Jacobian matrix, which describes the linear relationship between the model parameters (slowness parameters) and the observation data (propagation time), and in the embodiment, is specifically:

[0110] ;

[0111] , wherein represents the propagation angle of the 1st sound ray, represents the propagation angle of the 2nd sound ray, represents the propagation angle of the 3rd sound ray, represents the propagation angle of the 4th sound ray, represents the propagation angle of the 5th sound ray, represents the propagation angle of the 6th sound ray, represents the propagation angle of the 7th sound ray, represents the propagation angle of the 21st sound ray.

[0112] As can be seen, the 36 grids have 36 slownesses, that is, 36 unknowns, and after excluding the 2 grids through which no sound ray passes, there are 34, and the number of equations is only 21, and considering that the unknowns in the system are more and the equation set is an underdetermined problem (the number of equations is less than the number of unknowns), the regularization inversion method is used for solving in the embodiment.

[0113] S3, the water body vertical section temperature is calculated according to the water body vertical section sound speed.

[0114] After the slowness of each grid is obtained, the sound speed of each grid can be obtained, and finally, the temperature of each grid can be calculated according to the sound speed, depth and salinity of each grid.

[0115] The application uses the optical fiber phase change signal as the receiving device of the acoustic signal, instead of the originally high-cost and difficult-to-install acoustic device, realizes the large-range and high-precision detection of the water body temperature, by using the principle that the optical fiber phase change signal is deformed by the influence of the acoustic signal, resulting in the change of the optical fiber phase change signal.

[0116] Please refer to Figure 4 , based on the above method, the application further provides a water body vertical section temperature measurement system, the water body vertical section temperature measurement system comprises:

[0117] An acoustic conversion module is configured to acquire fiber phase variation signals of a plurality of fiber channels, and acquire a plurality of acoustic receiving signals according to the fiber phase variation signals.

[0118] A sound velocity calculation module is configured to acquire an acoustic emission signal corresponding to each of the acoustic receiving signals, acquire a plurality of propagation times according to the acoustic emission signal and the acoustic receiving signal, and acquire a water body vertical profile sound velocity according to the propagation times.

[0119] A temperature calculation module is configured to calculate a water body vertical profile temperature according to the water body vertical profile sound velocity.

[0120] It should be noted that the water body vertical profile temperature measurement method provided by the above embodiment and the water body vertical profile temperature measurement system belong to the same concept, and the specific implementation process is detailed in the water body vertical profile temperature measurement method, which will not be repeated here.

[0121] To sum up, the application uses the fiber phase variation signal as the receiving device of the acoustic signal, instead of the originally high-cost and difficult-to-install acoustic device, to realize large-range and high-precision detection of the water body temperature, by using the principle that the fiber phase variation signal is deformed by the acoustic signal, resulting in changes in the fiber phase variation signal.

[0122] It should be noted that in this document, the terms "comprise", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or terminal including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or terminal. Without more limitations, the element defined by the statement "comprises a" does not exclude the presence of another identical element in the process, method, article or terminal including the element.

[0123] Of course, those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by a computer program instructing related hardware (such as a processor, a controller, etc.), and the program can be stored in a computer-readable storage medium. The program can include the processes of the above-mentioned method embodiments when executed. The storage medium can be a memory, a disk, an optical disk, etc.

[0124] It should be understood that the application is not limited to the above examples, and those skilled in the art can make improvements or modifications according to the above description, and all these improvements and modifications shall fall within the protection scope of the claims of the application.

Claims

1. A method of measuring the vertical profile temperature of a body of water, characterized by, The method comprises the following steps: obtaining a plurality of fiber phase change signals of a plurality of fiber channels, and obtaining a plurality of acoustic receiving signals according to the fiber phase change signals; the obtaining of the plurality of fiber phase change signals comprises: deploying a distributed fiber acoustic wave sensing system comprising a host, a conversion cable and a sensitized marine cable, and sinking to the bottom of the water as an acoustic signal receiving end, wherein the sensitized marine cable adopts a spiral structure communication marine cable; a ship-borne active sound source emits a linear frequency modulation signal around the sensitized marine cable, and records the positioning information of the sound source through differential GPS; and the distributed fiber acoustic wave sensing system collects the fiber phase change signals of a plurality of fiber channels on the sensitized marine cable in real time; obtaining an acoustic emission signal corresponding to each acoustic receiving signal comprises: for each fiber channel, obtaining a peak delay time according to the acoustic receiving signal and the corresponding acoustic emission signal; for each fiber channel, obtaining a peak delay time of a set number of adjacent fiber channels, calculating the peak delay time of the fiber channel, and the average delay time of the peak delay times of each adjacent fiber channel; for each fiber channel, taking the corresponding average delay time as a propagation time; obtaining a plurality of propagation times according to each acoustic emission signal and each acoustic receiving signal, and obtaining a water body vertical profile sound speed according to each propagation time; calculating a water body vertical profile temperature according to the water body vertical profile sound speed.

2. The method of claim 1, wherein, The method of obtaining a plurality of acoustic receiving signals according to each fiber phase change signal comprises: For each of the fiber phase change signals, the length change of the fiber caused by the acoustic wave disturbance is calculated based on the fiber phase change signal: ,in, Indicates the phase change signal in the optical fiber Demodulation phase at time, Indicates the refractive index of the optical fiber. Indicates the laser wavelength. express The change in length of the optical fiber caused by acoustic wave disturbance at any given moment; calculating an axial strain of the optical fiber from the length change further calculating a sound velocity from the axial strain calculating a sound velocity from the axial strain ; a velocity of the sound wave as the acoustic receive signal.

3. The method of claim 1, wherein, The method of calculating the peak delay time of the fiber channel comprises: for each fiber channel, performing matched filtering on the acoustic receiving signal and the acoustic emission signal to obtain the correlation of each delay time, and calculating as follows: ， wherein is a delay time, a degree of correlation of the acoustic receive signal and the acoustic transmit signal in case of a match, denotes the acoustic receive signal at the time instant, denotes the complex conjugate of the acoustic transmit signal at the time instant; taking the delay with the highest correlation between each delay as the peak delay time.

4. The method of claim 1, wherein, The method of obtaining a water body vertical profile sound speed according to each propagation time comprises: dividing the water body vertical profile into a plurality of grids; calculating the slowness of each grid according to each propagation time: ， wherein, a vector representing the slowness composition of each grid, a vector representing the travel time composition of each grid, denotes the transpose, denotes the error matrix, is the error coefficient, denotes a matrix describing the relationship between travel time and slowness; for each grid, calculating the inverse of the slowness to obtain the sound speed of the grid; taking the combination of the sound speeds of each grid as the vertical profile sound speed.

5. The method of claim 4, wherein, The method of calculating a water body vertical profile temperature according to the water body vertical profile sound speed comprises: obtaining the salinity and depth of each grid, and for each grid, calculating the temperature of the grid according to the salinity, the depth and the sound speed; taking the combination of the temperatures of each grid as the water body vertical profile temperature.

6. The method of claim 1, wherein, Before obtaining a water body vertical profile sound speed according to each propagation time, the method further comprises: calculating the distance between each acoustic receiving position and the sound source according to the average delay time, and solving the distance equation between each fiber channel and a plurality of sound sources; based on the distance equation, combining each propagation time, and correcting the position of each fiber channel through a hypersurface intersection method or a Gauss-Markov estimator.

7. The method of claim 6, wherein, The hypersurface intersection method comprises: positioning the three-dimensional coordinates of the fiber channel by solving the distance equation, and calculating as follows: ， ， in, Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates the first One sound source Axis coordinates Indicates fiber channel Axis coordinates Indicates fiber channel Axis coordinates Indicates the relationship with the first The distance between the sound sources Indicates the speed of sound in the propagation medium. Indicates the fiber channel to the first The average delay time of each sound source; The Gauss-Markov estimator comprises: The Gaussian-Markov estimator is used to jointly invert the sound source position, the position of the optical fiber channel and the sound velocity; The sound source position and the position of the optical fiber channel are optimized based on the sensitivity cable design interval constraint; The three-dimensional shape of the optical fiber of the sensitivity cable is reconstructed by interpolation.

8. A water body vertical profile temperature measurement system, characterized by, The water body vertical section temperature measurement system is used to complete the water body vertical section temperature measurement method in any one of claims 1-7, comprising: An acoustic conversion module is configured to obtain optical fiber phase change signals of a plurality of optical fiber channels, and obtain a plurality of acoustic receiving signals according to the optical fiber phase change signals; A sound velocity calculation module is configured to obtain acoustic emission signals corresponding to each acoustic receiving signal, obtain a plurality of propagation times according to each acoustic emission signal and each acoustic receiving signal, and obtain a water body vertical section sound velocity according to each propagation time; A temperature calculation module is configured to calculate a water body vertical section temperature according to the water body vertical section sound velocity.

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