Monitoring method and low-altitude flying object positioning method based on distributed hydrophone optical cable

Abstract

The present invention relates to the field of optical fiber sensing, and provides a monitoring method based on distributed hydrophone optical cables and a method for locating low-altitude flying objects. The monitoring method comprises: using a phase-sensitive optical time domain reflectometry device to respectively collect DAS raw data generated by a plurality of underwater optical cables affected by a target sound source; laying a plurality of underwater optical cables in water according to a preset arrangement and distribution; performing time synchronization and noise reduction processing on each DAS raw data to obtain DAS analysis data; processing each DAS analysis data to obtain the azimuth of the target sound source relative to each underwater optical cable; locating the target sound source according to the preset arrangement and distribution and azimuth. Compared with the prior art, the present invention utilizes the property of the optical cable being sensitive to sound waves / vibrations during the transmission of optical signals, and uses each position point in the underwater optical cable as a hydrophone, so that the underwater optical cable forms a dense hydrophone array, thereby effectively improving the accuracy of hydrophone monitoring.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing, and more specifically, to a monitoring method based on a distributed hydrophone optical cable and a low-altitude flying object positioning method. Background Art

[0002] The hydrophone is one of the important devices used for underwater acoustic detection, and has important applications in the fields of marine disaster warning, resource exploration, fish positioning, and channel development. The optical cable hydrophone is an underwater acoustic signal sensor based on optical cables and optoelectronic technology. It converts the underwater acoustic vibration into an optical signal through high-sensitivity optical coherence detection technology, and transmits the optical signal to the signal processing system through the optical cable, and extracts the acoustic signal information through the signal processing system. However, conventional optical cable hydrophones mainly install hydrophone sensors on the optical cable, and convert the vibration signals received by the hydrophone sensors into optical signals. Although the hydrophone sensors can be evenly distributed on the optical cable, there is still a certain distance between each two hydrophone sensors, resulting in insufficient accuracy of the measurement results. Summary of the invention

[0003] The present invention aims to overcome at least one defect of the above-mentioned prior art and provide a monitoring method and a low-altitude flying object positioning method based on distributed hydroacoustic optical cables, so as to improve the accuracy of hydroacoustic monitoring.

[0004] The technical solution adopted by the present invention is:

[0005] A first aspect of the present invention provides a monitoring method based on a distributed hydrophone optical cable, the monitoring method comprising:

[0006] The DAS raw data of a plurality of underwater optical cables are collected respectively by a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution; the DAS raw data is generated by a target sound source acting on the corresponding underwater optical cables;

[0007] Performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables;

[0008] Processing each of the DAS analysis data respectively to obtain the azimuth of the target sound source relative to each of the underwater optical cables;

[0009] The target sound source is located according to the preset arrangement distribution and the azimuth.

[0010] By utilizing the property of the optical cable being sensitive to sound waves / vibrations during the optical signal transmission process, the DAS raw data of a plurality of the underwater optical cables are collected by a phase-sensitive optical time domain reflectometry device, and each position point in the underwater optical cable is used as a hydrophone. The interval between each position point in the underwater optical cable is very small, so that the underwater optical cables form a dense hydrophone array, thereby effectively improving the accuracy of hydrophone monitoring;

[0011] At the same time, by setting a plurality of the underwater optical cables in the water and laying the underwater optical cables in the water in a preset arrangement and distribution, the plurality of the underwater optical cables can realize the positioning of the target sound source from multiple angles through their arrangement and distribution, thereby further improving the accuracy of hydroacoustic monitoring.

[0012] Furthermore, the processing of each of the DAS analysis data specifically includes:

[0013] Acquire a signal vector of an external signal field in a spatial domain through a plurality of position points in a target interval in the underwater optical cable; the target interval is a section of the optical cable on the underwater optical cable that is acted upon by the target sound source; process the signal vector of each position point through a linear time-invariant filter to obtain the filtered signal vector;

[0014] Summing the signal vectors after each filtering process to obtain an array output of the target interval;

[0015] Restoring the DAS analysis data corresponding to the target interval through a delay-sum beamformer;

[0016] The frequency wave number response of each of the underwater optical cables is obtained according to the restored DAS analysis data and the array output.

[0017] Each position point in the underwater optical cable is used as a hydrophone, and the underwater optical cable is used as a hydrophone array. The array positioning method is used to calculate each position point in the underwater optical cable and the DAS analysis data of each position point, so that the underwater optical cable can be used as a hydrophone array to effectively realize the positioning of the target sound source.

[0018] Furthermore, the step of obtaining the azimuth of the target sound source relative to each of the underwater optical cables specifically includes:

[0019] The target frequency of the target sound source is obtained, and the azimuth of the target sound source relative to each of the position points in the target interval is obtained according to the target frequency and the corresponding frequency wave number response of the underwater optical cable.

[0020] Furthermore, the noise reduction processing of the DAS raw data specifically includes:

[0021] Obtaining standard background noise data of each of the underwater optical cables, wherein the standard background noise data is obtained by pre-performing a background noise test on each of the underwater optical cables;

[0022] The DAS raw data collected from each of the underwater optical cables is subtracted from the corresponding standard background noise data in the frequency domain.

[0023] By performing a noise floor test in advance to obtain standard noise floor data for each underwater optical cable, and then in the actual monitoring process, the obtained DAS raw data is subtracted from the standard noise floor data, which can effectively reduce the noise of the DAS raw data, improve the signal-to-noise ratio in the data, and thus improve the accuracy of hydroacoustic monitoring.

[0024] Further, the plurality of underwater optical cables include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable;

[0025] The arrangement and distribution specifically include:

[0026] The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise;

[0027] The third underwater optical cable is laid in a vertical direction.

[0028] By providing three underwater optical cables and arranging the three underwater optical cables to form a "coordinate system" structure, the positioning of the target sound source can be more conveniently achieved through the "coordinate system" structure.

[0029] Furthermore, locating the target sound source according to the preset arrangement distribution and the azimuth angle specifically includes:

[0030] Acquire a first lateral position and a second lateral position of the target sound source respectively according to the first underwater optical cable and the second underwater optical cable, and the corresponding azimuth angles;

[0031] Acquire the longitudinal position of the target sound source according to the third underwater optical cable and the corresponding azimuth;

[0032] The target sound source is positioned according to the first lateral position, the second lateral position and the longitudinal position.

[0033] In a second aspect of the present application, a monitoring system based on a distributed hydrophone optical cable is further provided, the monitoring system comprising:

[0034] A data acquisition module is used to respectively collect DAS raw data of a plurality of underwater optical cables through a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution; the DAS raw data is generated by a target sound source acting on the corresponding underwater optical cables;

[0035] A synchronous noise reduction module, used for performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables;

[0036] A data processing module, used to process each of the DAS analysis data respectively to obtain the azimuth of the target sound source relative to each of the underwater optical cables;

[0037] A sound source localization module is used to locate the target sound source according to the preset arrangement distribution and the azimuth.

[0038] According to a third aspect of the present application, a computer storage medium is provided, on which a computer-readable program is stored. When the computer-readable program is executed, the above-mentioned monitoring method based on distributed hydroacoustic optical cable is implemented.

[0039] The present application also provides a method for locating low-altitude flying objects based on a distributed hydroacoustic optical cable, the method comprising:

[0040] The DAS raw data of a plurality of underwater optical cables are collected respectively by a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution; the DAS raw data is generated by the sound source generated by the low-altitude flying object acting on the corresponding underwater optical cable;

[0041] Performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables;

[0042] Processing each of the DAS analysis data respectively to obtain the azimuth of the low-altitude flying object relative to each of the underwater optical cables;

[0043] The low-flying object is positioned according to the preset arrangement distribution and the azimuth.

[0044] Further, the plurality of underwater optical cables include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable; the arrangement and distribution specifically include:

[0045] The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise;

[0046] The third underwater optical cable is laid in a vertical direction.

[0047] The fourth aspect of the present application also provides an electronic device, including a memory and a processor, wherein the memory stores computer-readable instructions, and the processor executes the computer-readable instructions to implement the monitoring method based on the distributed hydroacoustic optical cable described in the first aspect, or the low-altitude flying object positioning method based on the distributed hydroacoustic optical cable described in the third aspect.

[0048] The fifth aspect of the present application further provides a computer storage medium having a computer-readable program stored thereon. When the computer-readable program is executed, it implements the monitoring method based on the distributed hydroacoustic optical cable described in the first aspect, or the low-altitude flying object positioning method based on the distributed hydroacoustic optical cable described in the third aspect.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. The present invention utilizes the property of optical cables being sensitive to sound waves / vibrations during the process of transmitting optical signals, collects DAS raw data of a plurality of underwater optical cables through phase-sensitive optical time domain reflectometry equipment, and uses each position point in the underwater optical cables as a hydrophone. The intervals between each position point in the underwater optical cables are very small, so that the underwater optical cables form a dense hydrophone array, thereby effectively improving the accuracy of hydrophone monitoring.

[0051] 2. The present invention lays three underwater optical cables in the water, and lays the three underwater optical cables in the water as a "coordinate system" structure, and the three underwater optical cables serve as three coordinate axes of the "coordinate system" structure. Then, the DAS raw data of the three underwater optical cables serving as coordinate axes can be used to achieve accurate positioning of the target sound source. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The present invention is a flow chart of the steps of the monitoring method.

[0053] Figure 2 It is a system structure diagram of the detection system of the present invention.

[0054] Figure 3 It is a device structure diagram of the electronic device of the present invention.

[0055] The accompanying drawings are marked with: data acquisition module 11, synchronous noise reduction module 12, data processing module 13, sound source localization module 14, memory 21, processor 22, bus 23, and communication interface 24. DETAILED DESCRIPTION

[0056] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0057] Example 1

[0058] The hydrophone is one of the important devices used for underwater acoustic detection, and has important applications in the fields of marine disaster warning, resource exploration, fish positioning, and channel development. The optical cable hydrophone is an underwater acoustic signal sensor based on optical cable and optoelectronic technology. It converts the underwater acoustic vibration into an optical signal through high-sensitivity optical coherence detection technology, and transmits the optical signal to the signal processing system through the optical cable, and extracts the acoustic signal information through the signal processing system. However, the conventional optical cable hydrophone mainly sets a hydrophone sensor on the optical cable, senses and receives the sound waves and vibrations in the water through the hydrophone sensor, and converts the received sound wave signal and vibration signal into an optical signal. In the specific setting, in order to improve the positioning accuracy of the hydrophone sensor, the hydrophone sensors are usually evenly laid on the optical cable, so that the hydrophone sensors laid on the optical cable can form a hydrophone monitoring array, and then the positioning of the target sound source in the water is realized through array positioning calculation. However, even if hydroacoustic sensors are evenly laid on the optical cable, due to the technical limitations of the hydroacoustic sensors, the hydrophones will not be too close to each other, which will eventually lead to a decrease in the positioning accuracy of hydroacoustic monitoring. At the same time, since a large number of hydroacoustic monitors need to be arranged on the optical cable to form a hydroacoustic monitoring array, this will greatly increase the cost of hydroacoustic monitoring.

[0059] Distributed Acoustic Sensing (DAS) based on phase-sensitive optical time-domain reflectometry (φ-OTDR) has attracted widespread attention due to its distributed acoustic wave restoration / monitoring capabilities. It can detect and locate any number of acoustic waves on long-distance sensing optical cables, and has advanced technologies such as long detection distance, high spatial resolution, and the ability to detect simultaneous vibrations at multiple points. Therefore, distributed acoustic wave sensing based on phase-sensitive optical time-domain reflectometry can be well applied to hydroacoustic monitoring, positioning, and tracking.

[0060] Based on the above distributed acoustic wave sensing principle, in order to solve the accuracy problem of hydroacoustic monitoring in the prior art, such as Figure 1 As shown, this embodiment provides a monitoring method based on a distributed hydroacoustic optical cable, the method comprising:

[0061] S1: collecting DAS raw data of a plurality of underwater optical cables respectively by using a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution;

[0062] In this embodiment, by connecting the phase-sensitive optical time domain reflection device to the underwater optical cable, utilizing the characteristics of the underwater optical cable that is sensitive to sound sources and vibrations, when the target sound source passes through, it will cause disturbances to the underwater optical cable. The phase-sensitive optical time domain reflection device is used to collect the DAS raw data generated by the disturbance in the underwater optical cable, and then the target sound source can be located.

[0063] It is understandable that the underwater optical cable itself is sensitive to sound waves and vibrations. Combined with the phase-sensitive optical time domain reflection setting, the entire underwater optical cable can be used to sense sound waves and vibrations. Specifically, the underwater optical cable realizes the sensing of sound waves and vibrations through the position points set on it, and the position points are set at a preset spacing on the underwater optical cable; in fact, the position point is the smallest unit on the underwater optical cable that can detect sound waves and vibrations, which can be understood as a very small length of an optical cable segment, wherein the preset spacing, that is, the length of the optical cable segment is determined according to the accuracy of the phase-sensitive optical time domain reflection device. Therefore, each position point on the underwater optical cable is equivalent to a hydrophone, and the position point of the underwater optical cable depends on the accuracy of the phase-sensitive optical time domain reflection device, so that the entire underwater optical cable can form a very dense hydrophone monitoring array. In the actual operation process, a specific interval on the underwater optical cable can be selected for demodulation, which is convenient for adjusting the array element aperture, array spacing, array aperture and other parameters of the hydrophone monitoring array to achieve more accurate positioning.

[0064] In this embodiment, the underwater optical cable can be suspended in water. Specifically, the underwater optical cable can be suspended in water by zero gravity or buoy suspension. Preferably, because the attenuation of high-frequency signals is large when sound waves are transmitted in water, in order to detect wide-band sounds on the water surface, the underwater optical cable is laid as close to the water surface as possible.

[0065] Preferably, the underwater optical cable is provided with a sensitivity-enhancing optical fiber, and the monitoring accuracy of the underwater optical cable can be improved by the sensitivity-enhancing optical fiber;

[0066] Further, in this embodiment, the laid multiple underwater optical cables may include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable, and the arrangement distribution may specifically be:

[0067] The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise;

[0068] The third underwater optical cable is laid along the vertical direction; preferably, the third underwater optical cable intersects with the intersection of the first horizontal direction and the second horizontal direction. The first underwater optical cable, the second underwater optical cable and the third underwater optical cable are laid crosswise to form a "coordinate system" structure, and the three underwater optical cables correspond to the three coordinate axes of the "coordinate system" structure respectively. The DAS raw data of the target sound source monitored by the three coordinate axes can more accurately realize the monitoring and positioning of the target sound source.

[0069] S2: performing time synchronization and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables;

[0070] Specifically, in the present embodiment, since each of the phase-sensitive optical time-domain reflectometer devices can only be connected to one of the underwater optical cables for collection, three of the underwater optical cables require three phase-sensitive optical time-domain reflectometer devices. Therefore, it is necessary to perform time synchronization on the DAS raw data collected by each of the phase-sensitive optical time-domain reflectometer devices to avoid asynchrony between the DAS raw data and cause positioning deviations. Specifically, a GPS module can be set in the phase-sensitive optical time-domain reflectometer device to add time information to the DAS raw data, so that the DAS raw data can be time-synchronized according to the time information.

[0071] At the same time, in this embodiment, the underwater optical cable set in the water may be affected by the noise on the water surface, in the water, and under the water, so before the actual monitoring, it is necessary to perform a background noise test on the underwater optical cable in the air, in the water, and when sinking to the bottom of the actual position set in advance to obtain the corresponding standard background noise data. After obtaining the standard background noise data, the DAS raw data collected for each underwater optical cable can be subtracted from the corresponding standard background noise data in the frequency domain to achieve noise reduction of the DAS raw data.

[0072] Finally, the DAS raw data is subjected to time synchronization and noise reduction processing to obtain the corresponding DAS analysis data.

[0073] S3: Processing each of the DAS analysis data respectively to obtain the azimuth of the target sound source relative to each of the underwater optical cables;

[0074] Specifically, in this embodiment, the processing of the DAS analysis data may include:

[0075] A signal vector of an external signal field in airspace is obtained through a plurality of position points in a target interval in the underwater optical cable; wherein the target interval is an optical cable segment on the underwater optical cable affected by the target sound source. Preferably, an optical cable segment on the underwater optical cable where the amplitude of the target sound source received exceeds a preset amplitude can be selected to ensure that effective DAS analysis data can be obtained.

[0076] The signal vector obtained in the target interval of each underwater optical cable can be expressed as:

[0077]

[0078] In the formula, represents the distance between the position point numbered n and the position point numbered 1, and t is the corresponding sampling time. Corresponding to the demodulated data of different optical cable sections.

[0079] Processing the signal vector of each of the position points through a linear time-invariant filter to obtain the filtered signal vector;

[0080] Among them, the impulse response of the linear time-invariant filter is , n represents the number of the corresponding position point;

[0081] The signal vectors after each filtering process are summed to obtain the array output of the target interval; it can be understood that the sum of the signal vectors is to sum the signal vectors corresponding to all position points on the target interval in the underwater optical cable to calculate the array output of the target interval.

[0082] Then the array output can be expressed as:

[0083]

[0084] Where N is the total number of location points. Indicates the delay at different locations. Different locations correspond to different delays.

[0085] The DAS analysis data corresponding to the target interval is restored through a delay-sum beamformer; specifically, in order to obtain the array output corresponding to the target interval, for the data of each underwater optical cable, the DAS analysis data of the target interval thereon is obtained and restored.

[0086] It can be expressed as:

[0087]

[0088] In the formula, represents the manifold vector, which can be specifically expressed as:

[0089]

[0090] Where k indicates that the popular vector belongs to the k domain (wave number domain), represents the transpose symbol; H represents the manifold vector symbol; J is a complex number, and e is the natural logarithm.

[0091]

[0092]

[0093]

[0094]

[0095] is the target frequency of the target sound source, μ is the direction cosine, c is the signal propagation speed of the corresponding medium, N is the total number of position points of the target interval of the underwater optical cable, is the direction angle of the target sound source relative to the corresponding position point, d is the distance between each position point in the target interval, Indicates the distance between the corresponding position point numbered n and the position point numbered 1. Indicates the delay of the location numbered n; Represents the transpose symbol.

[0096] The frequency wave number response of each of the underwater optical cables is obtained based on the restored DAS analysis data and array output.

[0097] In this embodiment, based on the above formula, we can assume a basis function: ; Where P represents the distance between any position point and the position point numbered 1;

[0098] According to the basis functions, combined with the array output, the response of each array to a plane wave can be expressed as ;

[0099] In the frequency domain, this response can be expressed as:

[0100] That is the frequency wave number response.

[0101] As described above, the frequency wavenumber response includes direction cosines, and the direction cosines include the azimuth of the target sound source relative to the corresponding position point, so after obtaining the frequency wavenumber response, the azimuth can be obtained based on the frequency wavenumber response.

[0102] The frequency wavenumber response reflects the spatial relationship in the frequency domain, so specifically, the acquisition of the direction angle may include acquiring the target frequency of the target sound source, and acquiring the azimuth of the target sound source relative to each position point in each of the underwater optical cables based on the target frequency and the corresponding frequency wavenumber response of the underwater optical cable.

[0103] S4: Positioning the target sound source according to the preset arrangement distribution and the azimuth angle.

[0104] Specifically, in this embodiment, accurate positioning can be achieved according to the "coordinate system" structure constructed by the three underwater optical cables, which may specifically include:

[0105] According to the first underwater optical cable and the second underwater optical cable, and the corresponding azimuth angles, the first lateral position and the second lateral position of the target sound source are respectively obtained; that is, the first underwater optical cable and the second underwater optical cable, which are laid along the first horizontal direction and the second horizontal direction and cross-arranged, are respectively used as the x-axis and y-axis of the "coordinate system" structure, and the target interval on the x-axis and the y-axis are respectively obtained, and the azimuth angles of the target sound source relative to the target interval are obtained according to the DAS analysis data of the obtained target interval, and the first lateral position and the second lateral position of the target sound source relative to the x-axis and the y-axis are obtained through the azimuth angles.

[0106] According to the third underwater optical cable and the corresponding azimuth, the longitudinal position of the target sound source is obtained; that is, the third underwater optical cable arranged in the vertical direction is used as the z-axis of the "coordinate system" structure, and on the basis of obtaining the first lateral position and the second lateral position, the target area on the z-axis is obtained, and the azimuth angle of the target sound source relative to the position point on the obtained target interval is obtained according to the DAS analysis data of the obtained target area, and the longitudinal distance of the target sound source can be obtained through the azimuth;

[0107] Finally, the target sound source is positioned according to the first lateral position, the second lateral position and the longitudinal position.

[0108] Example 2

[0109] Based on the same inventive concept as the embodiment, Figure 2 As shown, this embodiment provides a monitoring system based on a distributed hydroacoustic optical cable, and the monitoring system includes:

[0110] The data acquisition module 11 is used to respectively collect DAS raw data of a plurality of underwater optical cables through a phase-sensitive optical time domain reflectometer; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution;

[0111] In this embodiment, by connecting the phase-sensitive optical time domain reflection device to the underwater optical cable, utilizing the characteristics of the underwater optical cable that is sensitive to sound sources and vibrations, when the target sound source passes through, it will cause disturbances to the underwater optical cable. The phase-sensitive optical time domain reflection device is used to collect the DAS raw data generated by the disturbance in the underwater optical cable, and then the target sound source can be located.

[0112] It is understandable that the underwater optical cable itself is sensitive to sound waves and vibrations. Combined with the phase-sensitive optical time domain reflection setting, the entire underwater optical cable can be used to sense sound waves and vibrations. Specifically, the underwater optical cable realizes the sensing of sound waves and vibrations through the position points set on it, and the position points are set at a preset spacing on the underwater optical cable; in fact, the position point is the smallest unit on the underwater optical cable that can detect sound waves and vibrations, which can be understood as a very small length of an optical cable segment, wherein the preset spacing, that is, the length of the optical cable segment is determined according to the accuracy of the phase-sensitive optical time domain reflection device. Therefore, each position point on the underwater optical cable is equivalent to a hydrophone, and the position point of the underwater optical cable depends on the accuracy of the phase-sensitive optical time domain reflection device, so that the entire underwater optical cable can form a very dense hydrophone monitoring array. In the actual operation process, a specific interval on the underwater optical cable can be selected for demodulation, which is convenient for adjusting the array element aperture, array spacing, array aperture and other parameters of the hydrophone monitoring array to achieve more accurate positioning.

[0113] In this embodiment, the underwater optical cable can be suspended in water. Specifically, the underwater optical cable can be suspended in water by zero gravity or buoy suspension. Preferably, because the attenuation of high-frequency signals is large when sound waves are transmitted in water, in order to detect wide-band sounds on the water surface, the underwater optical cable is laid as close to the water surface as possible.

[0114] Preferably, the underwater optical cable is provided with a sensitivity-enhancing optical fiber, and the monitoring accuracy of the underwater optical cable can be improved by the sensitivity-enhancing optical fiber.

[0115] Further, in this embodiment, the laid multiple underwater optical cables may include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable, and the arrangement distribution may specifically be:

[0116] The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise;

[0117] The third underwater optical cable is laid along the vertical direction; preferably, the third underwater optical cable intersects with the intersection of the first horizontal direction and the second horizontal direction.

[0118] The first underwater optical cable, the second underwater optical cable and the third underwater optical cable are cross-laid to form a "coordinate system" structure. The three underwater optical cables correspond to the three coordinate axes of the "coordinate system" structure respectively. The DAS raw data of the target sound source monitored by the three coordinate axes can more accurately realize the monitoring and positioning of the target sound source.

[0119] A synchronization and noise reduction module 12 is used to perform time synchronization and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables;

[0120] Specifically, in the present embodiment, since each of the phase-sensitive optical time-domain reflectometer devices can only be connected to one of the underwater optical cables for collection, three of the underwater optical cables require three phase-sensitive optical time-domain reflectometer devices. Therefore, it is necessary to perform time synchronization on the DAS raw data collected by each of the phase-sensitive optical time-domain reflectometer devices to avoid asynchrony between the DAS raw data and cause positioning deviations. Specifically, a GPS module can be set in the phase-sensitive optical time-domain reflectometer device to add time information to the DAS raw data, so that the DAS raw data can be time-synchronized according to the time information.

[0121] At the same time, in this embodiment, the underwater optical cable set in the water may be affected by the noise on the water surface, in the water, and under the water, so before the actual monitoring, it is necessary to perform a background noise test on the underwater optical cable in the air, in the water, and when sinking to the bottom of the actual position set in advance to obtain the corresponding standard background noise data. After obtaining the standard background noise data, the DAS raw data collected for each underwater optical cable can be subtracted from the corresponding standard background noise data in the frequency domain to achieve noise reduction of the DAS raw data.

[0122] Finally, the DAS raw data is subjected to time synchronization and noise reduction processing to obtain the corresponding DAS analysis data.

[0123] A data processing module 13 is used to process each of the DAS analysis data respectively to obtain the azimuth of the target sound source relative to each of the underwater optical cables;

[0124] Specifically, in this embodiment, the processing of the DAS analysis data may include:

[0125] A signal vector of an external signal field in airspace is obtained through a plurality of position points in a target interval in the underwater optical cable; wherein the target interval is an optical cable segment on the underwater optical cable affected by the target sound source. Preferably, an optical cable segment on the underwater optical cable where the amplitude of the target sound source received exceeds a preset amplitude can be selected to ensure that effective DAS analysis data can be obtained.

[0126] The signal vector obtained in the target interval of each underwater optical cable can be expressed as:

[0127]

[0128] In the formula, represents the distance between the position point numbered n and the position point numbered 1, and t is the corresponding sampling time. Corresponding to the demodulated data of different optical cable sections.

[0129] Processing the signal vector of each of the position points through a linear time-invariant filter to obtain the filtered signal vector;

[0130] Among them, the impulse response of the linear time-invariant filter is , n represents the number of the corresponding position point;

[0131] The signal vectors after each filtering process are summed to obtain the array output of the target interval; it can be understood that the sum of the signal vectors is to sum the signal vectors corresponding to all position points on the target interval in the underwater optical cable to calculate the array output of the target interval.

[0132] Then the array output can be expressed as:

[0133]

[0134] Where N is the total number of location points. Indicates the delay at different locations. Different locations correspond to different delays.

[0135] The DAS analysis data corresponding to the target interval is restored through a delay-sum beamformer; specifically, in order to obtain the array output corresponding to the target interval, for the data of each underwater optical cable, the DAS analysis data of the target interval thereon is obtained and restored.

[0136] It can be expressed as:

[0137]

[0138] In the formula, represents the manifold vector, which can be specifically expressed as:

[0139]

[0140] Where k indicates that the popular vector belongs to the k domain (wave number domain), represents the transpose symbol; H represents the manifold vector symbol; J is a complex number, and e is the natural logarithm.

[0141]

[0142]

[0143]

[0144] is the target frequency of the target sound source, μ is the direction cosine, c is the signal propagation speed of the corresponding medium, N is the total number of position points of the target interval of the underwater optical cable, is the direction angle of the target sound source relative to the corresponding position point, d is the distance between each position point in the target interval, Indicates the distance between the corresponding position point numbered n and the position point numbered 1. Indicates the delay of the location numbered n; Represents the transpose symbol.

[0145] The frequency wave number response of each of the underwater optical cables is obtained based on the restored DAS analysis data and array output.

[0146] In this embodiment, based on the above formula, we can assume a basis function: ; Where P represents the distance between any position point and the position point numbered 1;

[0147] According to the basis functions, combined with the array output, the response of each array to a plane wave can be expressed as ;

[0148] In the frequency domain, this response can be expressed as:

[0149] That is the frequency wave number response.

[0150] As described above, the frequency wavenumber response includes direction cosines, and the direction cosines include the azimuth of the target sound source relative to the corresponding position point, so after obtaining the frequency wavenumber response, the azimuth can be obtained based on the frequency wavenumber response.

[0151] The frequency wavenumber response reflects the spatial relationship in the frequency domain, so specifically, the acquisition of the direction angle may include acquiring the target frequency of the target sound source, and acquiring the azimuth of the target sound source relative to each position point in each of the underwater optical cables based on the target frequency and the corresponding frequency wavenumber response of the underwater optical cable.

[0152] The sound source localization module 14 is used to locate the target sound source according to the preset arrangement distribution and the azimuth.

[0153] Specifically, in this embodiment, accurate positioning can be achieved according to the "coordinate system" structure constructed by the three underwater optical cables, which may specifically include:

[0154] According to the first underwater optical cable and the second underwater optical cable, and the corresponding azimuth angles, the first lateral position and the second lateral position of the target sound source are respectively obtained; that is, the first underwater optical cable and the second underwater optical cable, which are laid along the first horizontal direction and the second horizontal direction and cross-arranged, are respectively used as the x-axis and y-axis of the "coordinate system" structure, and the target interval on the x-axis and the y-axis are respectively obtained, and the azimuth angles of the target sound source relative to the target interval are obtained according to the DAS analysis data of the obtained target interval, and the first lateral position and the second lateral position of the target sound source relative to the x-axis and the y-axis are obtained through the azimuth angles.

[0155] According to the third underwater optical cable and the corresponding azimuth angle, the longitudinal position of the target sound source is obtained; that is, the third underwater optical cable arranged in the vertical direction is used as the z-axis of the "coordinate system" structure, and on the basis of obtaining the first lateral position and the second lateral position, the target interval on the z-axis is obtained, and the azimuth angle of the target sound source relative to the position point on the obtained target interval is obtained according to the DAS analysis data of the selected target interval, and the longitudinal distance of the target sound source can be obtained through the azimuth angle;

[0156] Finally, the target sound source is positioned according to the first lateral position, the second lateral position and the longitudinal position.

[0157] Example 3

[0158] Based on the same inventive concept as that of Example 1, this embodiment provides a method for locating low-altitude flying objects based on a distributed hydroacoustic optical cable;

[0159] In this embodiment, the characteristic frequency of low-altitude flying objects is generally in the range of 50Hz~2000Hz. The demodulation frequency of the DAS demodulation system carried in the phase-sensitive optical time domain reflectometer is related to the length of the detection optical cable. For an optical cable with a length of 25km, the maximum non-aliasing demodulation frequency is 2000Hz; for an optical cable with a length of 50km, the maximum non-aliasing demodulation frequency is 1000Hz. Therefore, without adding amplification and relay, the underwater optical cable can basically meet the detection requirements of the target sound source frequency.

[0160] At the same time, the sound intensity of low-altitude flying objects is generally above 120dB SPL. After the sound wave passes through the air-water interface, it is attenuated by about 60dB. The hydroacoustic optical cable and phase-sensitive optical time domain reflectometry equipment have the ability to monitor 60dB SPL sound pressure signals (water noise has been taken into account). Therefore, the monitoring method of this embodiment can effectively monitor low-altitude flying objects on the water surface and locate and track them.

[0161] Based on the above content and the inventive concept of Example 1, this embodiment provides a method for locating low-altitude flying objects based on a distributed hydroacoustic optical cable, and the positioning method specifically includes:

[0162] A1: DAS raw data of a plurality of underwater optical cables are collected respectively by a phase-sensitive optical time domain reflectometer; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution;

[0163] The DAS raw data is generated by the sound source generated by the low-altitude flying object acting on the corresponding underwater optical cable;

[0164] The specific content of step A1 can refer to the specific description of step S1 in embodiment 1;

[0165] A2: performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables;

[0166] The specific content of step A2 can refer to the specific description of step S2 in embodiment 1;

[0167] A3: Processing each of the DAS analysis data respectively to obtain the azimuth of the low-altitude flying object relative to each of the underwater optical cables;

[0168] The specific content of step A3 can refer to the specific description of step S3 in embodiment 1;

[0169] A4: Positioning the low-altitude flying object according to the preset arrangement distribution and the azimuth;

[0170] The specific content of step A4 can refer to the specific description of step S4 in embodiment 1.

[0171] Example 4

[0172] Based on the same inventive concept as the embodiment, Figure 3 The present embodiment provides an electronic device, including a memory 21 and a processor 22, wherein the memory 21 stores computer-readable instructions, and the processor 22 executes the computer-readable instructions to implement a monitoring method based on a distributed hydroacoustic optical cable as described in Example 1, or a low-altitude flying object positioning method based on a distributed hydroacoustic optical cable as described in Example 3.

[0173] Preferably, the electronic device further includes a bus 23 and a communication interface 24 , and the processor 22 , the communication interface 24 and the memory 21 are connected via the bus 23 .

[0174] The memory 21 may include a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk storage. The communication connection between the system network element and at least one other network element is realized through at least one communication interface 24 (which may be wired or wireless), and the Internet, wide area network, local area network, metropolitan area network, etc. may be used. The bus 23 may be an ISA bus, a PCI bus, or an EISA bus, etc. The bus 23 may be divided into an address bus, a data bus, a control bus, etc. (not fully drawn in the figure).

[0175] The processor 22 may be an integrated circuit chip with signal processing capability. In the specific implementation process, each step in the above method embodiment may be completed by the hardware integrated logic circuit or software instructions in the processor 22. The above processor 22 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, which may implement or execute the methods, steps, and logic diagrams disclosed in the embodiments of the present invention. The general-purpose processor may be a microprocessor or the processor 22 may also be any conventional processor 22, etc. The steps of the method disclosed in conjunction with the embodiments of the present invention may be directly embodied as being executed by a hardware decoding processor, or may be executed by a combination of hardware and software modules in a decoding processor. The software module may be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory 21, and the processor 22 reads the information in the memory 21 and completes the steps of the method of the above embodiment in combination with its hardware.

[0176] An embodiment of the present invention further provides a computer-readable storage medium, which stores computer-executable instructions. When the computer-executable instructions are called and executed by the processor 22, the computer-executable instructions prompt the processor 22 to implement the above-mentioned monitoring method based on distributed hydroacoustic optical cable, or the above-mentioned low-altitude flying object positioning method based on distributed hydroacoustic optical cable. The specific implementation can be found in the embodiments, which will not be repeated here.

[0177] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0178] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A monitoring method based on distributed hydrophone optical cable, characterized in that: The monitoring method comprises: The DAS raw data of a plurality of underwater optical cables are collected respectively by a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution; the DAS raw data is generated by a target sound source acting on the corresponding underwater optical cables; Performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables; Processing each of the DAS analysis data respectively to obtain the azimuth of the target sound source relative to each of the underwater optical cables; Positioning the target sound source according to the preset arrangement distribution and the azimuth; The processing of each of the DAS analysis data specifically includes: Acquiring a signal vector of an external signal field in airspace through a plurality of position points in a target interval in the underwater optical cable; the target interval is a section of the optical cable on the underwater optical cable that is affected by the target sound source; Processing the signal vector of each of the position points through a linear time-invariant filter to obtain the filtered signal vector; Summing the signal vectors after each filtering process to obtain the array output of the target interval; Restoring the DAS analysis data corresponding to the target interval through a delay-sum beamformer; Acquiring a frequency wavenumber response of each of the underwater optical cables according to the restored DAS analysis data and the array output; The obtaining of the azimuth of the target sound source relative to each of the underwater optical cables specifically includes: Acquire a target frequency of the target sound source, and acquire an azimuth of the target sound source relative to each of the position points in the target interval according to the target frequency and the corresponding frequency wave number response of the underwater optical cable; The plurality of underwater optical cables include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable; The arrangement and distribution specifically include: The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise; The third underwater optical cable is laid in a vertical direction.

2. A monitoring method based on distributed hydroacoustic optical cable according to claim 1, characterized in that: The noise reduction processing of the DAS raw data specifically includes: Obtaining standard background noise data of each of the underwater optical cables, wherein the standard background noise data is obtained by pre-performing a background noise test on each of the underwater optical cables; The DAS raw data collected from each of the underwater optical cables is subtracted from the corresponding standard background noise data in the frequency domain.

3. The monitoring method based on distributed hydroacoustic optical cable according to claim 1 is characterized in that: The positioning of the target sound source according to the preset arrangement distribution and the azimuth angle specifically includes: Acquire a first lateral position and a second lateral position of the target sound source respectively according to the first underwater optical cable and the second underwater optical cable, and the corresponding azimuth angles; Acquire the longitudinal position of the target sound source according to the third underwater optical cable and the corresponding azimuth; The target sound source is positioned according to the first lateral position, the second lateral position and the longitudinal position.

4. A monitoring system based on distributed hydrophone optical cable, characterized in that: The monitoring system comprises: A data acquisition module is used to respectively collect DAS raw data of a plurality of underwater optical cables through a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution; the DAS raw data is generated by a target sound source acting on the corresponding underwater optical cables; A synchronous noise reduction module, used for performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables; A data processing module, used to process each of the DAS analysis data respectively to obtain the azimuth of the target sound source relative to each of the underwater optical cables; A sound source localization module, used to locate the target sound source according to the preset arrangement distribution and the azimuth; The processing of each of the DAS analysis data specifically includes: Acquiring a signal vector of an external signal field in airspace through a plurality of position points in a target interval in the underwater optical cable; the target interval is a section of the optical cable on the underwater optical cable that is affected by the target sound source; Processing the signal vector of each of the position points through a linear time-invariant filter to obtain the filtered signal vector; Summing the signal vectors after each filtering process to obtain the array output of the target interval; Restoring the DAS analysis data corresponding to the target interval through a delay-sum beamformer; Acquiring a frequency wavenumber response of each of the underwater optical cables according to the restored DAS analysis data and the array output; The obtaining of the azimuth of the target sound source relative to each of the underwater optical cables specifically includes: Acquire a target frequency of the target sound source, and acquire an azimuth of the target sound source relative to each of the position points in the target interval according to the target frequency and the corresponding frequency wave number response of the underwater optical cable; The plurality of underwater optical cables include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable; The arrangement and distribution specifically include: The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise; The third underwater optical cable is laid in a vertical direction.

5. A monitoring system based on distributed hydroacoustic optical cable according to claim 4, characterized in that: The noise reduction processing of the DAS raw data specifically includes: Obtaining standard background noise data of each of the underwater optical cables, wherein the standard background noise data is obtained by pre-performing a background noise test on each of the underwater optical cables; The DAS raw data collected from each of the underwater optical cables is subtracted from the corresponding standard background noise data in the frequency domain.

6. A monitoring system based on distributed hydrophone optical cable according to claim 4, characterized in that: The positioning of the target sound source according to the preset arrangement distribution and the azimuth angle specifically includes: Acquire a first lateral position and a second lateral position of the target sound source respectively according to the first underwater optical cable and the second underwater optical cable, and the corresponding azimuth angles; Acquire the longitudinal position of the target sound source according to the third underwater optical cable and the corresponding azimuth; The target sound source is positioned according to the first lateral position, the second lateral position and the longitudinal position.

7. A method for locating low-altitude flying objects based on distributed hydrophone optical cables, characterized in that: The positioning method comprises: The DAS raw data of a plurality of underwater optical cables are collected respectively by a phase-sensitive optical time domain reflectometry device; the plurality of underwater optical cables are laid in the water according to a preset arrangement and distribution; the DAS raw data is generated by the sound source generated by the low-altitude flying object acting on the corresponding underwater optical cable; Performing time synchronization processing and noise reduction processing on each of the DAS raw data to obtain DAS analysis data corresponding to each of the underwater optical cables; Processing each of the DAS analysis data respectively to obtain the azimuth of the low-altitude flying object relative to each of the underwater optical cables; Positioning the low-altitude flying object according to the preset arrangement distribution and the azimuth; The processing of each of the DAS analysis data specifically includes: Acquire a signal vector of an external signal field in airspace through a plurality of position points in a target section of the underwater optical cable; the target section is a section of the optical cable on the underwater optical cable affected by the low-altitude flying object; Processing the signal vector of each of the position points through a linear time-invariant filter to obtain the filtered signal vector; Summing the signal vectors after each filtering process to obtain the array output of the target interval; Restoring the DAS analysis data corresponding to the target interval through a delay-sum beamformer; Acquiring a frequency wavenumber response of each of the underwater optical cables according to the restored DAS analysis data and the array output; The obtaining of the azimuth angle of the low-altitude flying object relative to each of the underwater optical cables specifically includes: Acquire the target frequency of the low-altitude flying object, and acquire the azimuth of the low-altitude flying object relative to each position point in the target interval according to the target frequency and the corresponding frequency wave number response of the underwater optical cable; The plurality of underwater optical cables include a first underwater optical cable, a second underwater optical cable and a third underwater optical cable; The arrangement and distribution specifically include: The first underwater optical cable is laid along a first horizontal direction; the second underwater optical cable is laid along a second horizontal direction; the first horizontal direction and the second horizontal direction are arranged crosswise; The third underwater optical cable is laid in a vertical direction.

8. The method for locating low-altitude flying objects based on distributed hydrophone optical cables according to claim 7 is characterized in that: The noise reduction processing of the DAS raw data specifically includes: Obtaining standard background noise data of each of the underwater optical cables, wherein the standard background noise data is obtained by pre-performing a background noise test on each of the underwater optical cables; The DAS raw data collected from each of the underwater optical cables is subtracted from the corresponding standard background noise data in the frequency domain.

9. The method for locating low-altitude flying objects based on distributed hydrophone optical cables according to claim 7, characterized in that: The positioning of the low-altitude flying object according to the preset arrangement distribution and the azimuth angle specifically includes: According to the first underwater optical cable and the second underwater optical cable, and the corresponding azimuth angles, respectively acquiring a first lateral position and a second lateral position of the low-altitude flying object; Acquire the longitudinal position of the low-altitude flying object according to the third underwater optical cable and the corresponding azimuth; The low-flying object is positioned according to the first lateral position, the second lateral position and the longitudinal position.

10. An electronic device comprising a memory and a processor, characterized in that: The memory stores computer-readable instructions, and the processor executes the computer-readable instructions to implement the monitoring method based on the distributed hydroacoustic optical cable as described in any one of claims 1 to 3, or to implement the low-altitude flying object positioning method based on the distributed hydroacoustic optical cable as described in any one of claims 7 to 9.

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