Sensitivity testing method for optical fiber curved surface array hydrophone

Abstract

The invention relates to the technical field of acoustic testing, in particular to a method for testing sensitivity of optical fiber curved surface array hydrophones, which comprises the following steps of: after determining coordinates of a sound source, each hydrophone of an optical fiber curved surface array and a standard hydrophone on a water test platform, transmitting a single-frequency pulse signal by the sound source; after the data acquisition system respectively acquires a signal received by the standard hydrophone and signals received by each hydrophone of the optical fiber curved surface array, the data analysis system generates an analog sound source signal, and direct waves received by the standard hydrophone and each hydrophone of the optical fiber curved surface array are quickly found by using a related algorithm; the optical fiber curved surface array hydrophone sensitivity testing method solves the problem of synchronization of different acquisition systems, is an effective supplement to an existing optical fiber curved surface array hydrophone sensitivity testing method, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of acoustic testing, and specifically relates to a method for testing the sensitivity of an optical fiber curved array hydrophone. Background Art

[0002] The fiber optic curved array is a new type of hydroacoustic sensor array, which is widely used in underwater target detection, ocean monitoring and national defense. It is combined with the head end of the underwater vehicle to form a fiber optic head end conformal array; it 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 sound signals. Through the sensitivity test, it can be verified whether the fiber optic hydrophone unit has the expected effect. Therefore, after the array is formed, the sensitivity of each hydrophone in the fiber optic curved array needs to be tested.

[0004] During the sensitivity test, the standard hydrophone directly obtains the sound pressure signal through the acquisition card, while the fiber optic curved array hydrophones extract the sound pressure signal through the soft demodulation algorithm, which requires first obtaining the phase information of the interference signal and then demodulating it into sound pressure information. There are algorithms such as filtering in this step.

[0005] Chinese patent with publication number CN114577323A proposes a device and method for measuring the sensitivity of a fiber optic hydrophone based on the reciprocal fringe method, but it is aimed at a single fiber optic hydrophone; Chinese patent with publication number CN117906741A proposes a device and method for measuring the low-frequency online sensitivity of a hydrophone array element, but it is aimed at a piezoelectric hydrophone array, and there is no problem of synchronization between different acquisition systems; Chinese patent with publication number CN115015894A discloses an online rapid test method for the phase consistency of a curved acoustic array hydrophone, which intercepts the direct band of the hydrophone receiving signal of the curved acoustic array facing the sound source area, calculates the correlation coefficient between each measured hydrophone signal and the reference hydrophone, and obtains the phase difference between each measured hydrophone and the reference hydrophone based on the correlation coefficient, but it is also aimed at a piezoelectric hydrophone array, and there is no problem of synchronization between different acquisition systems, and it is aimed at the phase consistency test of the curved array.

[0006] Therefore, for the sensitivity test of fiber optic curved surface array hydrophones, a test method is needed to solve the synchronization problem between the fiber optic curved surface array hydrophone data acquisition system and the standard hydrophone data acquisition system, to achieve rapid search of the direct wave signals of each fiber optic curved surface array hydrophone and the standard hydrophone, and to calculate the sensitivity of each fiber optic curved surface array hydrophone. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a sensitivity test method for a fiber optic curved array hydrophone, which adopts a correlation algorithm to solve the synchronization problem of different acquisition and demodulation systems, quickly find the direct waves received by the standard hydrophone and the hydrophones of the fiber optic curved array, and realize the sensitivity test of the fiber optic curved array hydrophone.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for testing the sensitivity of a fiber optic curved array hydrophone, the steps of which are:

[0009] Step 1: Determine the coordinates of the sound source, each hydrophone of the optical 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 acquisition system collects the signal received by the standard hydrophone, and the optical fiber curved array data acquisition system collects the signal received by each hydrophone of the optical fiber curved array;

[0011] Step 3: The data analysis system simulates and generates the sound source emission signal TS0;

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

[0013] Step 5: Use the sensitivity calculation formula to calculate the sensitivity of each hydrophone in the fiber optic curved array.

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

[0015]

[0016]

[0017] Among them, S ij Represents the coordinates of the hydrophone in the i-th row and j-th column of the fiber optic curved array.

[0018] In some of the embodiments, 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, the phase information in the interference signal is converted into a sound pressure signal through a demodulation algorithm.

[0019] In some embodiments, in step 3, the data analysis system simulates and generates the sound source emission signal TS according to the frequency (fk), period (T), wave number (N) of the sound source emission signal combined 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 acquisition time of the data acquisition system, sig(t) is the sinusoidal signal, and pulse(t) is the pulse signal. 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), wave number (N) of the transmitted signal and the sampling rate fs of the data acquisition system:

[0025]

[0026] In some embodiments, the correlation coefficient C between each hydrophone of the optical fiber curved surface array, the standard hydrophone and the simulated sound source in step 4 is ij Is the following formula:

[0027]

[0028]

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

[0030] Then the starting position of the direct wave received by each hydrophone in the optical 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, the sensitivity calculation formula in formula (11) is used in step 5 to obtain the phase shift sensitivity of each hydrophone in the optical fiber curved surface array,

[0035]

[0036] Where: M φij is the sensitivity of the hydrophone in the i-th row and j-th column of the optical fiber curved array, φ ij is the effective value of the phase shift of the interference light demodulated by the hydrophone in the i-th row and j-th column 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.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: after the coordinates of the sound source, each hydrophone of the optical fiber curved surface array, and the standard hydrophone are determined on the water test platform, the sound source emits a single-frequency pulse signal, and after the data acquisition system obtains the signal received by the standard hydrophone and the signal received by each hydrophone of the optical fiber curved surface array, the data analysis system uses a related algorithm to quickly find the direct waves received by the standard hydrophone and each hydrophone of the optical fiber curved surface array, thereby realizing the sensitivity test of the optical fiber curved surface array hydrophone, which is an effective supplement to the existing sensitivity test method of the optical fiber curved surface array hydrophone.

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

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

[0040] Figure 2 The signal collected by the data acquisition system;

[0041] Figure 3 Transmitting a signal for a simulated sound source;

[0042] Figure 4 Calculation of correlation coefficient between standard hydrophone and simulated sound source;

[0043] Figure 5 Schematic diagram of direct wave search using a standard hydrophone;

[0044] Figure 6 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] like Figure 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:

[0047] Step 1: Determine the coordinates of the sound source, each hydrophone of the optical fiber 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 collects the signal received by the standard hydrophone, and the optical fiber curved array data acquisition system collects the signal received by each hydrophone of the optical fiber 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 of each hydrophone of the optical fiber curved array and the direct waves of the standard hydrophone;

[0051] Step 5: Use the sensitivity calculation formula to calculate the sensitivity of each hydrophone in the fiber optic curved array.

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

[0053]

[0054]

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

[0056] In step 2, the standard hydrophone data acquisition system directly acquires the sound pressure signal of the standard hydrophone; after the optical fiber curved surface array data acquisition system acquires the interference signal of the optical fiber curved surface array hydrophone, the phase information in the interference signal is converted 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 according to the frequency (fk), period (T), and wave number (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 acquisition time of the data acquisition system, sig(t) is the sinusoidal signal, and pulse(t) is the pulse signal. 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), wave number (N) of the transmitted signal and the sampling rate fs of the data acquisition system:

[0063]

[0064] The correlation coefficient C between each hydrophone of the fiber optic curved array, the standard hydrophone and the simulated sound source in step 4 ij Is the following formula:

[0065]

[0066]

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

[0068] Then the starting position of the direct wave received by each hydrophone in 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 equation (11) can be used to obtain the phase shift sensitivity of each hydrophone in the optical fiber curved array:

[0073]

[0074] Where: M φij is the sensitivity of the hydrophone in the i-th row and j-th column of the optical fiber curved array, φ ij is the effective value of the phase shift of the interference light demodulated by the hydrophone in the i-th row and j-th column 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] Through this technical solution, the sensitivity of each hydrophone of the optical fiber curved array is tested on the water test platform. The specific method is as shown in the attached Figure 1 As shown, the center of the fiber optic curved array faces the sound source, and the angle between the normal direction of the curved surface and the direction of the sound source is near 0°. After placing the sound source at a position that meets the far-field condition, the coordinates of the sound source, the standard hydrophone, and each hydrophone of the fiber optic curved array are determined, and then the distance from the sound source to the standard hydrophone and the distance from the sound source to each hydrophone of the fiber optic curved array are calculated. The far-field condition position is when the distance between the sound source and the fiber optic curved array is greater than The position of the fiber, L is the maximum aperture of the fiber 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, NI collector, etc. In this example, the NI collector is selected; the fiber optic curved array data acquisition system will perform algorithm calculations after data acquisition to convert the collected interference information into sound pressure information. The data acquisition system transmits the collected data to the data analysis system in real time. Figure 2 As shown in the figure, the data collected by the standard hydrophone and the fiber optic curved array. In this example, the standard hydrophone and the fiber optic curved array are actually 1.5m apart. Theoretically, the direct wave interval is The general speed of sound is 1500m / s, so theoretically t=0.001s, but due to the problem of asynchronous acquisition system, the actual interval is about 0.12s.

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

[0078] The correlation algorithm is used to obtain the direct waves of each hydrophone of the optical fiber curved array and the direct waves of the standard hydrophone, such as Figure 4 As shown in the figure, taking the standard hydrophone as an example, the signal collected by the standard hydrophone is correlated with the simulated sound source signal. The maximum value of the area per second in the correlation calculation result is the starting point of the direct wave, as shown in the attached figure. Figure 5 As shown, in the first second, the sampling point 3276 is the point with the maximum correlation coefficient, which coincides with the starting point (3276) of the direct wave collected by the standard hydrophone. The direct waves received by each hydrophone of the optical fiber curved array are calculated similarly.

[0079] The sensitivity calculation of each hydrophone of the optical fiber curved surface array, in this example, selects 10 waves and calculates according to the following formula to quickly obtain the sensitivity of each hydrophone of the optical fiber curved surface array.

[0080]

[0081] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

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

Claims

1. A method for testing the sensitivity of a fiber optic curved array hydrophone, characterized in that: The steps are: Step 1: Determine the coordinates of the sound source, each hydrophone of the optical fiber 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 optical fiber curved array data acquisition system collects the signal received by each hydrophone of the optical fiber curved array; Step 3: The data analysis system simulates and generates the sound source emission signal TS0; Step 4: Obtain the direct waves of each hydrophone of the optical fiber curved array and the direct waves of the standard hydrophone; Step 5: Use the sensitivity calculation formula to calculate the sensitivity of each hydrophone in the fiber optic curved array.

2. A method for testing the sensitivity of a fiber optic curved array hydrophone according to claim 1, characterized in that: In step 1, the coordinates of the sound source are marked as S0 (x0, y0, z0), the coordinates of the standard hydrophone are marked as S1 (x1, y1, z1), and the coordinates of each hydrophone in the fiber optic curved array are marked as S ij (x ij ,y ij ,z ij ), calculate the distance d from the sound source to the standard hydrophone and the distance d from the sound source to each hydrophone of the fiber optic curved array according to the distance formula ij : Among them, S ij Represents the coordinates of the hydrophone in the i-th row and j-th column of the fiber optic curved array.

3. A method for testing the sensitivity of a fiber optic curved array hydrophone according to claim 2, characterized in that: In step 2, the standard hydrophone data acquisition system directly acquires the sound pressure signal of the standard hydrophone; after the optical fiber curved surface array data acquisition system acquires the interference signal of the optical fiber curved surface array hydrophone, the phase information in the interference signal is converted into a sound pressure signal through a demodulation algorithm.

4. A method for testing the sensitivity of a fiber optic curved array hydrophone according to claim 4, characterized in that: In step 3, the data analysis system simulates and generates the sound source emission signal TS0 according to the frequency (fk), period (T), wave number (N) of the sound source emission signal combined with the sampling rate fs of the data acquisition system. TS0(t)=sig(t).*pulse(t) (3) In formula (3), t is the acquisition time of the data acquisition system, sig(t) is the sinusoidal signal, and pulse(t) is the pulse signal. The mathematical expressions of the two are: sig(t)=cos(2pi*fk*t) (4) In formula (5), t0 is determined by the frequency (fk), wave number (N) of the transmitted signal and the sampling rate fs of the data acquisition system:

5. The method for testing the sensitivity of a fiber optic curved array hydrophone according to claim 1, characterized in that: The correlation coefficient C between each hydrophone of the fiber optic curved array, the standard hydrophone and the simulated sound source in step 4 ij Is the following formula: Where L is the sampling length, RS ij is the acoustic signal received by the hydrophone in the i-th row and j-th column of the optical fiber curved surface array, RS0 is the acoustic signal received by the standard hydrophone, k is the relevant time offset, and TS0[n+k] represents the value of the simulated sound source signal TS0 at time n+k; Then the starting position of the direct wave received by each hydrophone in the optical fiber curved array is recorded as: τ ij =argmax(C ij [k]) (9) The starting position of the direct wave received by the standard hydrophone is recorded as: τ0=argmax(C0[k]) (10).

6. The method for testing the sensitivity of a fiber optic curved array hydrophone according to claim 1, characterized in that: In step 5, the sensitivity calculation formula in equation (11) can be used to obtain the phase shift sensitivity of each hydrophone in the optical fiber curved array: M φij =20log10(φ ij )-20log10(U)+20log10(d ij )-20log10(d)+M0(11) Where: M φij is the sensitivity of the hydrophone in the i-th row and j-th column of the optical fiber curved array, φ ij is the effective value of the phase shift of the interference light demodulated by the hydrophone in the i-th row and j-th column 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.

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