A device and method for measuring the sensitivity of optical fiber hydrophone based on reciprocity fringe method

Abstract

The present invention belongs to the field of acoustic metrology and testing technology, and specifically relates to a fiber optic hydrophone sensitivity measurement device and method based on reciprocal fringes. The device and method comprise an auxiliary transducer, a reciprocal transducer, a signal transmitter, a power amplifier, a current sampler, a laser, a photoelectric converter, a multi-channel signal acquisition processor, and the like. The device and method obtain the phase shift sensitivity of the fiber optic hydrophone by measuring three stages: the emission current of the auxiliary transducer and the open-circuit voltage of the reciprocal transducer, the emission current of the auxiliary transducer and the optical phase shift of the fiber optic hydrophone, and the emission current of the reciprocal transducer and the optical phase shift of the fiber optic hydrophone, combined with the free-field reciprocity constant. The present invention breaks with the original measurement method of the fiber optic hydrophone, utilizes the principle of sound field reciprocity and the principle of fiber optic hydrophone interference fringes, and introduces the reciprocal transducer as a key instrument for fiber optic hydrophone sensitivity measurement in the measurement method for the first time. The device has the advantages of high measurement accuracy and a large measurable dynamic range.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic measurement and testing, and in particular relates to a device and method for measuring the sensitivity of an optical fiber hydrophone based on reciprocity fringes. Background Art

[0002] Compared to traditional piezoelectric hydrophones, fiber-optic hydrophones offer numerous advantages, including immunity to electromagnetic interference, electrical insulation, corrosion resistance, high safety, high sensitivity, wide frequency response, compact size, light weight, ease of reuse, and ease of forming large-scale arrays. Consequently, their application in defense has become increasingly widespread, and they have become a key development direction for modern sonar. In 1976, after Bucaro et al. at the U.S. Naval Research Laboratory published the world's first paper on fiber-optic hydrophones, countries in Europe and the United States invested significant human, material, and financial resources in research and testing of fiber-optic hydrophones and arrays. Research and development of fiber-optic hydrophones in China started relatively late, with the first domestic sea trials of fiber-optic hydrophone arrays conducted in August 2002.

[0003] Interferometric fiber-optic hydrophones generally refer to interferometric fiber-optic hydrophone probes. Their principle is to convert sound pressure in water into optical phase changes. The ability of a fiber-optic hydrophone to detect optical phase changes, known as phase sensitivity, is a key indicator of the acoustic performance of a fiber-optic hydrophone probe. Currently, methods for calibrating the phase sensitivity of interferometric fiber-optic hydrophones include the Bessel function ratio method, phase-generated carrier (PGC) modulation and demodulation, and interference fringe counting. The Bessel function ratio method uses the ratio of the high-frequency components of the interferometric light intensity to determine the phase shift of the interferometric light intensity. Combined with the sound pressure measured by a standard hydrophone, the phase sensitivity of the interferometric fiber-optic hydrophone is obtained. This method offers advantages such as a simple optical system and easy operation. However, the Bessel function ratio is multi-valued, requiring a pre-determined signal interval within which the optical phase shift occurs. Furthermore, it cannot obtain the time-domain waveform of the acoustic wave. The PGC modulation and demodulation method uses high-frequency signal modulation and demodulation to determine the phase shift of an interferometric fiber optic hydrophone. This method can avoid interference from low-frequency external vibration signals, but its optical system is complex, requires multiple devices, and is expensive. It also cannot demodulate large acoustic wave signals. The interference fringe counting method uses the relationship between the time-domain image of the interference light intensity and the carrier modulation intensity to determine the phase shift of the interference light intensity. The phase shift sensitivity of the fiber optic hydrophone is then calculated using the sound pressure measured by a standard hydrophone.

[0004] In summary, current interferometric fiber optic hydrophone calibration methods rely on comparison methods, which cannot achieve accurate sensitivity measurements. This invention organically utilizes the principle of acoustic field reciprocity and the principle of fiber optic hydrophone interference fringes, overcoming the technical difficulties of absolute measurement using fiber optic hydrophones. Summary of the Invention

[0005] In view of the above, the present invention provides a fiber optic hydrophone sensitivity measurement device and method based on the reciprocity fringe method, which can achieve absolute measurement of the phase shift sensitivity of the fiber optic hydrophone and improve the measurement precision and accuracy of the phase shift sensitivity of the fiber optic hydrophone.

[0006] The present invention provides the following technical solutions:

[0007] A fiber optic hydrophone sensitivity measurement device based on the reciprocal fringe method includes: an auxiliary transducer for converting electrical signals into acoustic signals and radiating acoustic waves in water; a reciprocal transducer for mutual conversion between electrical signals and acoustic signals, radiating acoustic waves in water, or receiving acoustic waves in water and converting the received acoustic waves into electrical signals U1; a signal transmitter for generating a single-frequency pulse signal with functions such as adjusting signal frequency, amplitude, and pulse width; a power amplifier for amplifying the power of the single-frequency pulse signal and loading it onto the auxiliary transducer or the reciprocal transducer. two ends; a current sampler for sampling the single-frequency pulse signal after power amplification to generate a corresponding electrical signal U2, which represents the emission current signal of the auxiliary transducer or the reciprocal transducer; a laser for generating an optical signal; a photoelectric converter, one end of which is provided with a fiber optic hydrophone, and the photoelectric converter is used to convert the interference light signal of the fiber optic hydrophone into an electrical signal U3; a multi-channel signal acquisition processor for sampling the electrical signals U1, U2, and U3, and processing the signals to obtain the phase shift sensitivity of the fiber optic hydrophone;

[0008] The output end of the signal transmitter is connected to the output end of the power amplifier, the positive pole of the output end of the power amplifier is connected to the positive pole of the auxiliary transducer through the current sampler, the negative pole of the output end of the power amplifier is directly connected to the negative pole of the auxiliary transducer, the output end of the current sampler is connected to one input end of the multi-channel signal acquisition processor, and the positive and negative poles of the reciprocal transducer are connected to the other input end of the multi-channel signal acquisition processor through a coaxial cable.

[0009] Preferably, the non-reciprocity of the reciprocal transducer is within 0.3 dB.

[0010] Preferably, the power amplifier has an impedance matching function, and its power amplification of the electrical signal is linear amplification.

[0011] Preferably, the sampling frequency of the multi-channel signal acquisition processor is more than 100 times the frequency of the acoustic signal.

[0012] Preferably, the fiber optic hydrophone adopts an interference fiber optic hydrophone probe.

[0013] A method for measuring the sensitivity of a fiber-optic hydrophone based on the reciprocal fringe method described above is provided. The fiber-optic hydrophone sensitivity measurement device measures the phase shift sensitivity of the fiber-optic hydrophone by performing three-stage measurements: the emission current of the auxiliary transducer and the open-circuit voltage of the reciprocal transducer, the emission current of the auxiliary transducer and the optical phase shift of the fiber-optic hydrophone, and the emission current of the reciprocal transducer and the optical phase shift of the fiber-optic hydrophone. The method then combines the free-field reciprocity constant to obtain the phase shift sensitivity of the fiber-optic hydrophone. The specific implementation method is as follows:

[0014] Step 1: Place the auxiliary transducer and the reciprocal transducer in water. The distance d1 between the two satisfies the far-field condition. The auxiliary transducer radiates sound waves into the water. The amplitude of the auxiliary transducer's transmitting current I0 is measured. The amplitude of the reciprocal transducer's receiving electrical signal U1 is U FH ;

[0015] Step 2: Remove the reciprocal transducer and place the fiber optic hydrophone in the position where the reciprocal transducer was previously placed. Adjust the transmitting current of the auxiliary transducer so that the interference fringes of the fiber optic hydrophone interference signal are nπ, where n is an integer greater than 0. Record the amplitude I1 of the transmitting current at this time.

[0016] Step 3: Remove the auxiliary transducer and place the reciprocal transducer in water at a distance d2 from the fiber optic hydrophone. Similarly, adjust the transmitting current of the reciprocal transducer so that the interference fringes of the fiber optic hydrophone interference signal are mπ, where m is an integer greater than 0. Record the transmitting current I2 at this time. The sensitivity of the fiber optic hydrophone is:

[0017]

[0018] Where J is the free field reciprocity constant, which is Where ρ is the density in water, which is 1000 kg / m 3 ; f is the frequency of the sound wave.

[0019] Furthermore, during the entire measurement process, the fiber optic hydrophone showed no nonlinearity, which was verified by the following method:

[0020] During the measurement process of step 2, when the measured phase shift is π, the emission current amplitude of the auxiliary transducer (4) is I π1 ,like When , it indicates that the optical fiber hydrophone (5) is in a linear state. Similarly, in the measurement process of step 3, when the measured phase shift is π, the emission current amplitude of the auxiliary transducer (4) is I π2 ,like When , it indicates that the optical fiber hydrophone (5) is in a linear state.

[0021] Furthermore, the interference fringes of the optical fiber hydrophone interference signal are measured as follows: the amplitudes of adjacent non-maximum peaks and troughs are set to be equal, and the number of maximum peaks between the two is n1, then the phase shift of the interference signal at this time is n1π.

[0022] Furthermore, the auxiliary transducer and the reciprocal transducer are both within a linear operating range during the entire measurement process, and their total harmonic distortion is no more than 3%.

[0023] Furthermore, the phase shift of the optical fiber hydrophone is in a linear state within 3π.

[0024] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0025] The present invention breaks the original measurement method of fiber optic hydrophones, organically utilizes the principle of sound field reciprocity and the principle of fiber optic hydrophone interference fringes, and introduces the reciprocal transducer as a key instrument for fiber optic hydrophone sensitivity measurement in the measurement method for the first time. It has the advantages of high measurement accuracy and a large measurable dynamic range. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a module diagram of the optical fiber hydrophone sensitivity measurement device of the present invention;

[0027] Figure 2 Schematic diagram of interference signal when the phase shift is π according to the present invention;

[0028] Figure 3 This is a schematic diagram of the interference signal when the phase shift is 3π according to the present invention.

[0029] The following are marked in the figure:

[0030] 1-Signal transmitter; 2-Power amplifier; 3-Current sampler; 4-Auxiliary transducer; 5-Fiber optic hydrophone; 6-Photoelectric converter; 7-Multi-channel signal acquisition processor; 8-Reciprocal transducer; 9-Laser. DETAILED DESCRIPTION

[0031] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings so that those skilled in the art can more clearly understand how to practice the present invention. Although the present invention has been described with reference to its preferred embodiments, these embodiments are merely illustrative and are not intended to limit the scope of the present invention.

[0032] Combined with attachment Figure 1As shown, a fiber optic hydrophone sensitivity measurement device based on the reciprocal fringe method includes: an auxiliary transducer 4 for converting an electrical signal into an acoustic signal and radiating an acoustic wave in water; a reciprocal transducer 8 for converting electrical signals and acoustic signals to each other, radiating an acoustic wave in water, or receiving an acoustic wave in water and converting the received acoustic wave into an electrical signal U1; a signal transmitter 1 for generating a single-frequency pulse signal with functions such as adjusting the signal frequency, amplitude, and pulse width; a power amplifier 2 for amplifying the power of the single-frequency pulse signal and loading it on both ends of the auxiliary transducer 4 or the reciprocal transducer 8. end; a current sampler 3 for sampling the single-frequency pulse signal after power amplification to generate a corresponding electrical signal U2, which represents the emission current signal of the auxiliary transducer 4 or the reciprocal transducer 8; a laser 9 for generating an optical signal; a photoelectric converter 6, one end of which is provided with a fiber optic hydrophone 5, and the photoelectric converter 6 is used to convert the interference light signal of the fiber optic hydrophone 5 into an electrical signal U3; a multi-channel signal acquisition processor 7 for sampling the electrical signals U1, U2, and U3, and processing the signals to obtain the phase shift sensitivity of the fiber optic hydrophone 5;

[0033] The output end of the signal transmitter 1 is connected to the output end of the power amplifier 2, the positive pole of the output end of the power amplifier 2 is connected to the positive pole of the auxiliary transducer 4 through the current sampler 3, the negative pole of the output end of the power amplifier 2 is directly connected to the negative pole of the auxiliary transducer 4, the output end of the current sampler 3 is connected to the input end B of the multi-channel signal acquisition processor 7, and the positive and negative poles of the reciprocal transducer 8 are connected to the input end A of the multi-channel signal acquisition processor 7 through a coaxial cable.

[0034] Specifically, the non-reciprocity of the reciprocal transducer 8 is within 0.3 dB.

[0035] Specifically, the power amplifier 2 has an impedance matching function, and its power amplification of the electrical signal is linear amplification.

[0036] Specifically, the sampling frequency of the multi-channel signal acquisition processor 7 is more than 100 times the frequency of the acoustic signal.

[0037] Specifically, the fiber optic hydrophone 5 adopts an interference fiber optic hydrophone probe.

[0038] A method for measuring the sensitivity of a fiber optic hydrophone based on the reciprocal fringe method described above is provided. The fiber optic hydrophone sensitivity measurement device measures the phase shift sensitivity of the fiber optic hydrophone by measuring three stages: the emission current of the auxiliary transducer 4 and the open-circuit voltage of the reciprocal transducer 8; the emission current of the auxiliary transducer 4 and the optical phase shift of the fiber optic hydrophone 5; and the emission current of the reciprocal transducer 8 and the optical phase shift of the fiber optic hydrophone 5. The method is specifically implemented as follows:

[0039] Step 1: Place the auxiliary transducer 4 and the reciprocal transducer 8 in the water, with a distance d1 between them, sufficient for both to be in each other's far field. Set up the signal transmitter 1 to generate a sinusoidal pulse signal with a frequency of f. After amplification by the power amplifier 2, it acts on the fiber optic hydrophone 5, causing the fiber optic hydrophone 5 to generate an acoustic wave signal in the water. Under the action of the acoustic wave, the reciprocal transducer 8 generates an electrical signal U1 due to the piezoelectric effect. The multi-channel signal acquisition processor 7 converts U1 into a digital signal through AD, and calculates the amplitude U of the electrical signal U1 through Fourier transform. FH At the same time, the transmitting current U2 of the auxiliary transducer 4 measured by the current sampler 3 is converted into a digital signal by the multi-channel signal acquisition processor 7, and its amplitude I1 is calculated by Fourier transform.

[0040] Step 2: Take the reciprocal transducer 8 out of the water, and place the fiber optic hydrophone 5 at the position where the reciprocal transducer 8 was taken out, connect the optical output end of the fiber optic hydrophone 5 to the input end of the photoelectric converter 6, connect the output signal of the photoelectric converter 6 to the input end A of the multi-channel signal acquisition processor 7, and connect the laser 9 to the optical input end of the fiber optic hydrophone 5. Similarly, set the signal transmitter 1 to generate a sinusoidal pulse signal with a frequency of f, which generates an acoustic wave signal after power amplification. The acoustic wave acts on the fiber optic hydrophone 5 to change the length of the optical fiber, thereby causing the phase shift of the optical interference signal to change. The interference signal of the fiber optic hydrophone 5 is observed through the multi-channel signal acquisition processor 7. When there is only an extreme peak between the non-maximum peaks and troughs in the fringes of the interference signal, the interference signal is as follows: Figure 2 As shown, the phase shift at this time is π, and the multi-channel signal acquisition processor 7 is used to collect the emission current signal U2 of the auxiliary transducer 4 at this time and calculate its amplitude I π1 , adjust the amplitude of the sinusoidal pulse signal through the signal transmitter 1, and observe the interference signal of the optical fiber hydrophone 5 through the multi-channel signal acquisition processor 7 until the multi-channel signal acquisition processor 7 appears Figure 3 The interference fringes shown in FIG. 3 indicate that the optical phase shift is 3π at this time. The multi-channel signal acquisition processor 7 collects the emission current signal U2 of the auxiliary transducer 4 at this time and calculates its amplitude I1. If the value of d1 is less than 0.3dB, it indicates that the test is valid and the measurement in step 3 can be performed. Otherwise, change d1 and repeat the measurement in steps 1 and 2.

[0041] Step 3: Take out the auxiliary transducer 4, connect the negative pole of the reciprocal transducer 8 to the negative pole of the power amplifier 2, and connect the positive pole of the reciprocal transducer 8 to the current sampler 3. Place the reciprocal transducer 8 in water, and the distance between the reciprocal transducer 8 and the fiber optic hydrophone 5 is d2. Set the signal transmitter 1 to generate a sinusoidal pulse signal with a frequency of f, and after power amplification, the auxiliary transducer 4 generates an acoustic wave signal. Adjust the amplitude of the sinusoidal pulse signal, and observe the interference signal of the fiber optic hydrophone 5 through the multi-channel signal acquisition processor 7 until the multi-channel signal acquisition processor 7 appears. Figure 2 The interference signal shown in , then the phase shift at this time is π, the multi-channel signal acquisition processor 7 is used to collect the emission current signal U2 of the reciprocal transducer 8 at this time and calculate its amplitude I π2 , adjust the amplitude of the sinusoidal pulse signal through the signal transmitter 1, and observe the interference signal of the optical fiber hydrophone 5 through the multi-channel signal acquisition processor 7 until the multi-channel signal acquisition processor 7 appears Figure 3 The interference fringes shown,

[0042] That is, the optical phase shift at this time is 3π, and the current signal U2 generated by the reciprocal transducer 8 at this time is collected by the multi-channel signal acquisition processor 7 and its amplitude I2 is calculated. If the value is less than 0.3dB, the sensitivity M of the fiber optic hydrophone can be calculated. Φ for:

[0043]

[0044] Specifically, during the entire measurement process, the fiber optic hydrophone showed no nonlinearity, which was verified by the following method:

[0045] During the measurement process of step 2, when the measured phase shift is π, the emission current amplitude of the auxiliary transducer 4 is I π1 ,like When , it indicates that the optical fiber hydrophone 5 is in a linear state; in the measurement process of step 3, when the measured phase shift is π, the emission current amplitude of the auxiliary transducer 4 is I π2 ,like , it indicates that the optical fiber hydrophone 5 is in a linear state.

[0046] Specifically, the method for measuring the interference fringes of the interference signal of the optical fiber hydrophone 5 is as follows: the amplitudes of adjacent non-maximum peaks and troughs are set to be equal, and the number of maximum peaks between the two is n1, then the phase shift of the interference signal at this time is n1π.

[0047] Specifically, the auxiliary transducer 4 and the reciprocal transducer 8 are both within the linear operating range during the entire measurement process, and the total harmonic distortion thereof is no greater than 3%.

[0048] Specifically, the phase shift of the optical fiber hydrophone 5 is in a linear state within 3π.

[0049] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A fiber optic hydrophone sensitivity measurement device based on the reciprocity fringe method, characterized in that: include: The auxiliary transducer (4) is used to convert the electric signal into an acoustic signal and radiate the acoustic wave in water; the reciprocal transducer (8) is used to convert the electric signal into an acoustic signal, radiate the acoustic wave in water, or receive the acoustic wave in water and convert the received acoustic wave into the electric signal U1; the signal transmitter (1) is used to generate a single-frequency pulse signal; the power amplifier (2) is used to amplify the power of the single-frequency pulse signal and load it on both ends of the auxiliary transducer (4) or the reciprocal transducer (8); the current sampler (3) is used to perform current sampling on the single-frequency pulse signal after power amplification. Sampling to generate a corresponding electrical signal U2, which represents the emission current signal of the auxiliary transducer (4) or the reciprocal transducer (8); a laser (9), used to generate an optical signal; a photoelectric converter (6), wherein one end of the photoelectric converter (6) is provided with a fiber optic hydrophone (5), and the photoelectric converter (6) is used to convert the interference light signal of the fiber optic hydrophone (5) into an electrical signal U3; a multi-channel signal acquisition processor (7), used to sample the electrical signals U1, U2, and U3, and process the signals to obtain the phase shift sensitivity of the fiber optic hydrophone (5); The output end of the signal transmitter (1) is connected to the input end of the power amplifier (2); the positive electrode of the output end of the power amplifier (2) passes through the current sampler (3) and is connected to the positive electrode of the auxiliary transducer (4); the negative electrode of the output end of the power amplifier (2) is directly connected to the negative electrode of the auxiliary transducer (4); the output end of the current sampler (3) is connected to an input end of a multi-channel signal acquisition processor (7); and the positive and negative electrodes of the reciprocal transducer (8) are connected to the other input end of the multi-channel signal acquisition processor (7) via a coaxial cable; The optical fiber hydrophone sensitivity measurement device measures the optical fiber hydrophone's phase shift sensitivity by combining the free-field reciprocity constant with the emission current of the auxiliary transducer (4) and the open-circuit voltage of the reciprocal transducer (8), the emission current of the auxiliary transducer (4) and the optical phase shift of the optical fiber hydrophone (5), and the emission current of the reciprocal transducer (8) and the optical phase shift of the optical fiber hydrophone (5) in three stages.

2. The optical fiber hydrophone sensitivity measurement device based on the reciprocity fringe method according to claim 1, characterized in that: The non-reciprocity of the reciprocal transducer (8) is within 0.3 dB.

3. The optical fiber hydrophone sensitivity measurement device based on the reciprocity fringe method according to claim 1, characterized in that: The power amplifier (2) has an impedance matching function, and its power amplification of the electrical signal is linear amplification.

4. The device for measuring the sensitivity of a fiber-optic hydrophone based on the reciprocity fringe method according to claim 1, characterized in that: The sampling frequency of the multi-channel signal acquisition processor (7) is more than 100 times the frequency of the acoustic signal.

5. The optical fiber hydrophone sensitivity measurement device based on the reciprocity fringe method according to claim 1, characterized in that: The optical fiber hydrophone (5) adopts an interference type optical fiber hydrophone probe.

6. The method for measuring the sensitivity of a fiber-optic hydrophone based on the reciprocity fringe method according to claim 1, characterized in that: The specific implementation is as follows: Step 1: Place the auxiliary transducer (4) and the reciprocal transducer (8) in water, with the distance d1 between them satisfying the far-field condition. The auxiliary transducer (4) radiates sound waves into the water, and the amplitude of the transmitting current I0 of the auxiliary transducer (4) and the amplitude of the receiving electrical signal U1 of the reciprocal transducer (8) are measured to be U FH ; Step 2: Take out the reciprocal transducer (8), and place the fiber optic hydrophone (5) at the position where the reciprocal transducer (8) was previously placed, adjust the emission current of the auxiliary transducer (4) so ​​that the interference fringes of the interference signal of the fiber optic hydrophone (5) are nπ, where n is an integer greater than 0, and record the amplitude I1 of the emission current at this time; Step 3: Take out the auxiliary transducer (4) and place the reciprocal transducer (8) in water. The distance between the reciprocal transducer (8) and the optical fiber hydrophone (5) is d2. Similarly, adjust the emission current of the reciprocal transducer (8) so that the interference fringes of the interference signal of the optical fiber hydrophone (5) are mπ, where m is an integer greater than 0. Record the emission current I2 at this time. The sensitivity of the optical fiber hydrophone (5) is: Where J is the free field reciprocity constant, which is Where ρ is the density in water, which is 1000 kg / m 3 ;f is the frequency of the sound wave; During the measurement process of step 2, when the phase shift is measured at π, the emission current amplitude of the auxiliary transducer (4) is Iπ1. If When , it indicates that the optical fiber hydrophone (5) is in a linear state; in the measurement process of step 3, when the measured phase shift is π, the emission current amplitude of the reciprocal transducer (8) is Iπ2, if When , it indicates that the optical fiber hydrophone (5) is in a linear state.

7. The method for measuring the sensitivity of a fiber optic hydrophone based on the reciprocity fringe method according to claim 6, characterized in that: The method for measuring the interference fringes of the interference signal of the optical fiber hydrophone (5) is as follows: the amplitudes of adjacent non-maximum peaks and troughs are set to be equal, and the number of maximum peaks between the two is n1, then the phase shift of the interference signal at this time is n1π.

8. The method for measuring the sensitivity of a fiber optic hydrophone based on the reciprocity fringe method according to claim 6, characterized in that: The auxiliary transducer (4) and the reciprocal transducer (8) are both within a linear operating range during the entire measurement process, and their total harmonic distortion is no more than 3%.

9. The method for measuring the sensitivity of a fiber optic hydrophone based on the reciprocity fringe method according to claim 6, characterized in that: The phase shift of the optical fiber hydrophone (5) is in a linear state within 3π.

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