A method for testing sensitivity of a fiber-optic curved array hydrophone

Abstract

The present application relates to the technical field of acoustic testing, and especially relates to a kind of sensitivity testing method of optical fiber curved array hydrophone, after determining the coordinates of sound source, optical fiber curved array hydrophone and standard hydrophone on water test platform, sound source emits single-frequency pulse signal, after data acquisition system obtains the signal received by standard hydrophone and the signal received by optical fiber curved array hydrophone respectively, data analysis system generates analog sound source signal, and direct wave received by standard hydrophone and optical fiber curved array hydrophone is quickly found using correlation algorithm, and the sensitivity testing of optical fiber curved array hydrophone is realized, the present application solves the synchronization problem of different acquisition systems, is an effective supplement to the existing sensitivity testing method of optical fiber curved array hydrophone, and has wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acoustic testing, and in particular to a sensitivity testing method for a fiber-optic curved array hydrophone. BACKGROUND

[0002] The fiber-optic curved array is a new type of underwater acoustic sensing array, which is widely used in underwater target detection, ocean monitoring and national defense. It is combined with the front end of an underwater vehicle to form a fiber-optic front-end conformal array, and is placed on the side of the underwater vehicle to form a fiber-optic side array.

[0003] The sensitivity of the fiber-optic curved array directly determines its ability to perceive weak acoustic signals. Through sensitivity testing, it can be verified whether the fiber-optic hydrophone unit has the expected effect, so after the array is formed, the sensitivity of each hydrophone of the fiber-optic curved array needs to be tested.

[0004] During sensitivity testing, the standard hydrophone directly acquires the sound pressure signal through a collection card, while the fiber-optic curved array hydrophone extracts the sound pressure signal through a soft demodulation algorithm, which needs to first acquire the phase information of the interference signal and then demodulate it into sound pressure information. This step involves filtering and other algorithms.

[0005] Chinese Patent No. CN114577323A proposes a fiber-optic hydrophone sensitivity measurement device and method based on the reciprocity fringe method, but it is for a single fiber-optic hydrophone. Chinese Patent No. CN117906741A proposes a device and method for measuring the low-frequency online sensitivity of a hydrophone array element, but it is for a piezoelectric hydrophone array, and there is no synchronization problem between different collection systems. Chinese Patent No. CN115015894A discloses a curved surface acoustic array hydrophone phase consistency online fast testing method, which intercepts the direct wave band of the hydrophone receiving signal of the curved surface acoustic array facing the sound source area, calculates the correlation coefficient of each measured hydrophone signal and the reference hydrophone, and obtains the phase difference between each measured hydrophone and the reference hydrophone according to the correlation coefficient, but it is also for a piezoelectric hydrophone array, and there is no synchronization problem between different collection systems. Moreover, it is for curved array phase consistency testing.

[0006] Therefore, for fiber-optic curved array hydrophone sensitivity testing, a testing method is needed to solve the synchronization problem between the fiber-optic curved array hydrophone data collection system and the standard hydrophone data collection system, to realize fast searching of the direct wave signals of the fiber-optic curved array hydrophones and the standard hydrophone, and to calculate the sensitivity of each fiber-optic curved array hydrophone. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application aims to provide a fiber curved array hydrophone sensitivity test method, which uses a correlation algorithm to solve the synchronization problem of different collection and demodulation systems and quickly find the direct waves received by the standard hydrophone and each hydrophone of the fiber curved array, thereby realizing fiber curved array hydrophone sensitivity test.

[0008] To achieve the above object, the present application provides the following technical scheme: a fiber curved array hydrophone sensitivity test method, comprising the following steps:

[0009] Step 1: determining the coordinates of the sound source, each hydrophone of the fiber curved array and the standard hydrophone on the water test platform;

[0010] Step 2: the sound source emits a single-frequency pulse signal, the standard hydrophone data collection system collects the signal received by the standard hydrophone, and the fiber curved array data collection system collects the signal received by each hydrophone of the fiber curved array;

[0011] Step 3: the data analysis system simulates the generation of the sound source emission signal TS0;

[0012] Step 4: obtaining the direct waves of each hydrophone of the fiber curved array and the direct wave of the standard hydrophone;

[0013] Step 5: calculating the sensitivity of each hydrophone of the fiber curved array by using a sensitivity calculation formula.

[0014] In some embodiments, in step 1, the coordinates of the sound source are denoted as S0(x0, y0, z0), the coordinates of the standard hydrophone are denoted as S1(x1, y1, z1), and the coordinates of each hydrophone of the fiber curved array are denoted as S ij (x ij ,y ij ,z ij ), the distance d from the sound source to the standard hydrophone and the distance d ij from the sound source to each hydrophone of the fiber curved array are calculated according to the distance formula:

[0015]

[0016]

[0017] wherein S ij represents the coordinates of the i-th row and j-th column hydrophone of the fiber curved array.

[0018] In some embodiments, in step 2, the standard hydrophone data collection system directly collects the sound pressure signal of the standard hydrophone; after the fiber curved array data collection system collects the interference signal of the fiber curved array hydrophone, the phase information in the interference signal is converted into a sound pressure signal by using a demodulation algorithm.

[0019] In some embodiments, in step 3, the data analysis system generates the acoustic source emission signal TS0 according to the frequency (fk), period (T), and wave number (N) of the acoustic source emission signal in combination with the sampling rate fs of the data acquisition system

[0020] TS0(t) = sig(t) * pulse(t) (3)

[0021] In formula (3), t is the data acquisition time of the data acquisition system, sig(t) is a sinusoidal signal, and pulse(t) is a pulse signal, and the mathematical expressions of the two are:

[0022] sig(t) = cos(2pi*fk*t) (4)

[0023]

[0024] In formula (5), t0 is determined by the frequency (fk) of the emission signal, the wave number (N), and the sampling rate fs of the data acquisition system:

[0025]

[0026] In some embodiments, in step 4, the correlation coefficient C of each hydrophone of the fiber curved array, the standard hydrophone, and the simulated acoustic source ij is as follows:

[0027]

[0028]

[0029] where L is the sampling length, RS ij is the acoustic signal received by the i-th row j-th column hydrophone of the fiber curved array, RS0 is the acoustic signal received by the standard hydrophone, k is the time offset of the correlation, and TS0[n+k] represents the value of the simulated acoustic source signal TS0 at time n+k;

[0030] The starting position of the direct wave received by each hydrophone of the fiber curved array is recorded as:

[0031] τ ij = argmax(C ij [k]) (9)

[0032] The starting position of the direct wave received by the standard hydrophone is recorded as:

[0033] τ0 = argmax(C0[k]) (10).

[0034] In some embodiments, in step 5, the sensitivity calculation formula in formula (11) is used to obtain the phase shift sensitivity of each hydrophone of the fiber curved array,

[0035]

[0036] Wherein: M φij is the sensitivity of the i-th row j-th column hydrophone in the optical fiber curved array, φ ij is the effective value of the phase shift of the interference light demodulated by the i-th row j-th column hydrophone in the optical fiber curved array, U is the effective value of the open circuit voltage received by the standard hydrophone, and M0 is the sensitivity of the standard hydrophone.

[0037] Compared with the prior art, the beneficial effects of the present application are that after the coordinates of the sound source, the hydrophones of the optical fiber curved array and the standard hydrophone are determined on the water test platform, the sound source emits a single frequency pulse signal, the data acquisition system acquires the signals received by the standard hydrophone and the hydrophones of the optical fiber curved array, and then the data analysis system quickly finds the direct wave received by the standard hydrophone and the hydrophones of the optical fiber curved array by using a correlation algorithm, thereby realizing the sensitivity test of the hydrophones of the optical fiber curved array and effectively supplementing the existing sensitivity test method of the hydrophones of the optical fiber curved array.

[0038] The details of one or more embodiments of the present application are presented in the following drawings and description to make the other features, purposes and advantages of the present application more clear, concise and easy to understand, and to make the present application more fully described and understood through the embodiments of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a sensitivity test diagram of the optical fiber curved array;

[0040] Figure 2 is the signal acquired by the data acquisition system;

[0041] Figure 3 is the signal emitted by the simulated sound source;

[0042] Figure 4 is the correlation coefficient calculation of the standard hydrophone and the simulated sound source;

[0043] Figure 5 is a direct wave searching diagram of the standard hydrophone;

[0044] Figure 6 is a flowchart of the present application. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0046] AsFigure 6 As shown, the present invention provides a technical solution: a method for testing the sensitivity of a fiber optic curved array hydrophone, the steps of which are as follows:

[0047] Step 1: Determine the coordinates of the sound source, each hydrophone in the fiber optic curved array, and the standard hydrophone on the water test platform;

[0048] Step 2: The sound source emits a single-frequency pulse signal, the standard hydrophone data acquisition system acquires the signal received by the standard hydrophone, and the fiber optic curved array data acquisition system acquires the signal received by each hydrophone in the fiber optic curved array.

[0049] Step 3: The data analysis system simulates and generates the sound source emission signal TS0;

[0050] Step 4: Obtain the direct waves from each hydrophone in the fiber optic curved array and the direct waves from the standard hydrophone;

[0051] Step 5: Calculate the sensitivity of each hydrophone in the fiber optic curved array using the sensitivity calculation formula.

[0052] In step 1, the coordinates of the sound source are denoted as S0(x0,y0,z0), the coordinates of the standard hydrophone are denoted as S1(x1,y1,z1), and the coordinates of each hydrophone in the fiber optic curved array are denoted as S... ij (x ij ,y ij ,z ij The distance d from the sound source to the standard hydrophone and the distance d from the sound source to each hydrophone in the fiber optic curved array are calculated according to the distance formula. ij :

[0053]

[0054]

[0055] Among them, S ij The coordinates of the hydrophone in the i-th row and j-th column of the fiber optic curved array are represented.

[0056] In step 2, the standard hydrophone data acquisition system directly acquires the sound pressure signal of the standard hydrophone; after the fiber optic curved array data acquisition system acquires the interference signal of the fiber optic curved array hydrophone, it converts the phase information in the interference signal into a sound pressure signal through a demodulation algorithm.

[0057] In step 3, the data analysis system simulates and generates the sound source emission signal TS0 based on the frequency (fk), period (T), and wavenumber (N) of the sound source emission signal, combined with the sampling rate fs of the data acquisition system.

[0058] TS0(t)=sig(t).*pulse(t) (3)

[0059] In formula (3), t is the data acquisition system acquisition time, sig(t) is a sinusoidal signal, pulse(t) is a pulse signal, and the mathematical expressions of the two are:

[0060] sig(t) = cos(2pi*fk*t) (4)

[0061]

[0062] In formula (5), t0 is determined by the frequency (fk) of the transmitted signal, the wave number (N), and the sampling rate fs of the data acquisition system:

[0063]

[0064] The correlation coefficient C of the optical fiber curved array hydrophone, the standard hydrophone, and the simulated sound source in step 4 is as follows: ij

[0065]

[0066]

[0067] where L is the sampling length, RS ij is the sound signal received by the i-th row j-th column hydrophone of the optical fiber curved array, RS0 is the sound signal received by the standard hydrophone, k is the time offset of the correlation, and TS0[n+k] represents the value of the simulated generated sound source signal TS0 at time n+k;

[0068] The starting position of the direct wave received by each hydrophone of the optical fiber curved array is recorded as:

[0069] τ ij = argmax(C ij [k]) (9)

[0070] The starting position of the direct wave received by the standard hydrophone is recorded as:

[0071] τ0= argmax(C0[k]) (10).

[0072] In step 5, the sensitivity calculation formula in formula (11) is used to obtain the phase shift sensitivity of each hydrophone of the optical fiber curved array,

[0073]

[0074] where M φij is the sensitivity of the i-th row j-th column hydrophone of the optical fiber curved array, φ ij is the effective value of the phase shift of the interference light demodulated by the i-th row j-th column hydrophone of the optical fiber curved array, U is the effective value of the open-circuit voltage received by the standard hydrophone, and M0 is the sensitivity of the standard hydrophone. ​

[0075] By the technical solution, the sensitivity of each hydrophone of the fiber curved array is tested on the water test platform, and the specific method is shown in the accompanying drawings. Figure 1 The fiber curved array is centrally opposite to the sound source position, the included angle between the normal direction of the curved surface of the fiber curved array and the direction of the sound source is near 0°, the sound source is placed at a position satisfying the far field condition, and then the coordinates of the sound source, the standard hydrophone and each hydrophone of the fiber curved array are determined, and the distance from the sound source to the standard hydrophone and the distance from the sound source to each hydrophone of the fiber curved array are calculated. The position satisfying the far field condition is a position where the distance between the sound source and the fiber curved array is greater than , L is the maximum aperture of the fiber curved surface, and λ is the signal wavelength.

[0076] In the data acquisition system, the data acquisition system of the standard hydrophone can be an oscilloscope, an NI collector and the like, and in this example, an NI collector is selected; the data acquisition system of the fiber curved array will perform algorithm operation after data acquisition, and converts the collected interference information into sound pressure information. The data acquisition system transmits the collected data to the data analysis system in real time. As shown in the drawings, the data collected by the standard hydrophone and the fiber curved array, in this example, the standard hydrophone and the fiber curved array are actually 1.5 m apart, and the theoretical direct wave interval is Figure 2 The general sound velocity is 1500 m / s, so theoretically t=0.001 s, but due to the problem of asynchronous collection system, the actual interval is about 0.12 s.

[0077] The data analysis system, in this example, a computer is selected; the simulation generates a sound source emission signal TS0, taking the frequency fk=6000 Hz, the wave number N=15, the emission period T=1 s and the sampling rate fs=50 kHz of the data acquisition system as an example, the simulated sound signal is as shown in the drawings. Figure 3

[0078] The correlation algorithm is used to obtain the direct wave of each hydrophone of the fiber curved array and the direct wave of the standard hydrophone, as shown in the drawings, taking the standard hydrophone as an example, the signal collected by the standard hydrophone is correlated with the simulated sound source signal, and the maximum value of each second region in the correlation calculation result is the starting point of the direct wave, as shown in the drawings. Figure 4 In the first second, the sampling point 3276 is the maximum point of the correlation coefficient, which coincides with the starting point (3276) of the direct wave collected by the standard hydrophone, and the direct wave received by each hydrophone of the fiber curved array is calculated in a similar manner. Figure 5

[0079] The sensitivity of each hydrophone of the fiber curved array is calculated, in this example, 10 waves are selected to calculate according to the following formula, and the sensitivity of each hydrophone of the fiber curved array is quickly obtained.

[0080] ​​​

[0081] The above embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

[0082] Although the embodiments of the present application have been shown and described, it should be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for testing sensitivity of a fiber-optic curved array hydrophone, the method comprising: The steps are: Step 1: determining the coordinates of the sound source, the hydrophones of the fiber-optic curved array and the standard hydrophone on the water test platform; Step 2: the sound source emits a single-frequency pulse signal, the standard hydrophone data acquisition system collects the signal received by the standard hydrophone, and the fiber-optic curved array data acquisition system collects the signal received by each hydrophone of the fiber-optic curved array; Step 3: Data analysis system simulates generation of acoustic source emission signal ; Step 4: using a correlation algorithm to obtain the direct wave received by the standard hydrophone and each hydrophone of the fiber-optic curved array; Correlation coefficient of fiber optic curved array hydrophone, standard hydrophone and simulated sound source in step 4 is of the formula: （7） （8） where L is the sampling length, is the acoustic signal received by the i-th row j-th column hydrophone of the fiber optic curved array, is the acoustic signal received by a standard hydrophone, and k is the time offset of the correlation, denotes the analog generated acoustic source signal at time n + k. The starting position of the direct wave received by each hydrophone of the fiber-optic curved array is recorded as: （9） The starting position of the direct wave received by the standard hydrophone is recorded as: （10）； Step 5: calculating the sensitivity of each hydrophone of the fiber-optic curved array using a sensitivity calculation formula.

2. The method of claim 1, wherein: In step 1, the coordinates of the sound source are denoted as , the coordinates of the standard hydrophone are denoted as , the coordinates of each hydrophone of the fiber curved array are denoted as , and the distance d from the sound source to the standard hydrophone and the distance d i from the sound source to each hydrophone of the fiber curved array are calculated according to the distance formula : （1） （2） where S ij represents the coordinates of the hydrophone in the i-th row and j-th column of the fiber-optic curved array.

3. The method of claim 2, wherein: In step 2, the standard hydrophone data acquisition system directly collects the sound pressure signal of the standard hydrophone; after the fiber-optic curved array data acquisition system collects the interference signal of the hydrophone of the fiber-optic curved array, the phase information in the interference signal is converted into a sound pressure signal through a demodulation algorithm.

4. The method of claim 3, wherein: In step 3, the data analysis system simulates the sound source emission signal according to the frequency , period T, and wave number N of the sound source emission signal in combination with the sampling rate fs of the data acquisition system （3） In formula (3), t is the data acquisition system acquisition time, is a sine signal, is a pulse signal, and the mathematical expressions of the two are: （4） （5） In formula (5): The frequency of the emitted signal The wave number N and the sampling rate fs of the data acquisition system determine: （6）。 5. The method of claim 1, wherein: In step 5, the phase shift sensitivity of each hydrophone of the fiber-optic curved array can be obtained by using the sensitivity calculation formula in formula (11), （11） Wherein: is the sensitivity of the i-th row j-th column hydrophone in the fiber-optic curved array, is the effective value of the phase shift of the interference light demodulated by the i-th row j-th column hydrophone in the fiber-optic curved array, is the effective value of the open-circuit voltage received by the standard hydrophone, is the sensitivity of the standard hydrophone.

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