A self-calibration high intensity fiber hydrophone based on end-face reflection principle

Abstract

The application provides a self-calibration high-intensity optical fiber hydrophone based on an end face reflection principle and relates to the technical field of hydrophones.The application comprises the following steps: a laser light source emits a first laser beam, a fiber optical isolator inhibits reflection and outputs a second laser beam, a fiber adjustable optical attenuator adjusts incident power and outputs a third laser beam, a 1x2 fiber coupler divides the third laser beam into a fourth laser beam and a fifth laser beam, a first photoelectric detector monitors power, a fiber circulator transmits the fifth laser beam to a fiber sensing module, generates reflected light and transmits the reflected light to a second photoelectric detector, and the second photoelectric detector converts the reflected light into a voltage signal, a data acquisition card acquires the signal, a signal demodulation processing unit calculates sound pressure sensitivity according to a mapping relationship formula of the voltage signal and the sound pressure, and a standard voltage module provides a standard voltage for the data acquisition card.The application solves the problems that a high-intensity hydrophone cannot be reused and cannot be self-calibrated after being damaged in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrophone, in particular to a self-calibration high-intensity optical fiber hydrophone based on end face reflection principle. BACKGROUND

[0002] High Intensity Focused Ultrasound (HIFU-High Intensity Focused Ultrasound) has the characteristics of strong directivity, good penetration, focus, no radiation, etc., and is widely used in medical fields such as tumor treatment, ultrasonic lithotripsy, and tissue destruction. HIFU technology focuses high-intensity focused ultrasound waves on the lesion site, uses high-heat effect, cavitation effect, mechanical effect and acoustic chemical effect to cause coagulation necrosis of the target tumor tissue, so as to achieve the purpose of "removing" the lesion, and provides a non-invasive or minimally invasive method for treating diseased tissues, which has been paid more and more attention and developed in recent years.

[0003] In order to ensure the accuracy of HIFU treatment dose and the safety of treatment, it is necessary to accurately measure the peak sound pressure and sound pressure spatial distribution of HIFU sound field, that is, to realize the quantitative measurement of HIFU sound field distribution. The existing quantitative measurement of HIFU sound field distribution is usually obtained by three-dimensional scanning using a high-intensity hydrophone. High-intensity hydrophone is a kind of hydrophone used for high sound pressure measurement, including needle-shaped hydrophone with protective shell and membrane hydrophone, hydrophone based on sound wave reflection or scattering, and optical fiber hydrophone, etc. Compared with ordinary piezoelectric hydrophone, it is more suitable for high sound pressure environment. However, due to the negative pressure phase of HIFU focal region causing cavitation effect, the cavitation bubble is violently inflated and collapsed under the action of positive / negative pressure of sound wave, producing transient high temperature (>5000 K), high pressure (>1 GPa) and shock wave, which also easily leads to the depolarization of sensitive elements of traditional piezoelectric high-intensity hydrophone (such as PZT ceramic) or dielectric breakdown (such as PVDF film), causing damage or reducing the service life.

[0004] The maximum measurable sound pressure amplitude of needle-shaped and membrane hydrophone with protective shell reaches 20 MPa, which prevents the direct action of cavitation and shock wave by covering a metal protective layer on the surface of piezoelectric vibration element to improve the damage threshold, but will reduce the bandwidth of the hydrophone and affect the flatness of its frequency response. The reflection or scattering type high-intensity hydrophone avoids the destructive damage caused by direct measurement by arranging reflection / scattering bodies to avoid the sound focus position of the receiving surface, but the size of the reflection / scattering body affects the sensitivity, spatial resolution and bandwidth of the hydrophone, which needs to be considered to obtain the best measurement ability.

[0005] Compared with piezoelectric sensing technology, the fiber hydrophone generally uses a single-mode optical fiber as a sensitive element, and provides a solution for accurate measurement of the HIFU complex sound field by virtue of its physical characteristics of high pressure resistance, high temperature resistance and cavitation impact resistance, the inhibition ability of the fiber core ultra-micropore diameter (4.4 μm) to the space average effect, and the advantages of wide frequency band, high dynamic range and anti-electromagnetic interference. The sound pressure sensitivity is the main technical index of the hydrophone, which is defined as the ratio of the output voltage of the hydrophone to the acting sound pressure, and the accuracy thereof directly determines the accuracy of the measured sound pressure, so that the calibration is generally used after the calibration of the calibration laboratory.

[0006] The Fabry-Perot fiber hydrophone is an interference type fiber hydrophone, which is based on the Fabry-Perot interference principle, and a Fabry-Perot cavity is constructed by constructing two low reflectivity and parallel end faces at the end of the optical fiber, that is, the Fabry-Perot cavity. The reflected light of the laser beam incident to the two end faces returns along the original path and interferes. When the sound pressure between the two end faces changes, the distance between the end faces also changes, thereby causing the change of the interference signal intensity. The measured sound pressure is obtained by solving the relationship between the interference signal intensity and the sound pressure. The determination of the sound pressure sensitivity needs to be realized by a certain calibration method through the calibration laboratory;

[0007] The Fabry-Perot fiber hydrophone depends on the design and performance of the cavity and the reflecting end face to a great extent due to the complex structure, and the manufacturing process is complex, so that the Fabry-Perot resonant cavity cannot be reused after being damaged, and can only be re-produced or scrapped, thereby the use cost is high. SUMMARY

[0008] In order to overcome the deficiencies of the prior art, the purpose of the present application is to provide a self-calibration high-strength fiber hydrophone based on the end face reflection principle, which solves the problems of the prior art that the high-strength hydrophone cannot be reused after being damaged and cannot be self-calibrated.

[0009] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0010] A self-calibration high-strength fiber hydrophone based on the end face reflection principle, comprising:

[0011] A laser light source, a fiber optical isolator, a fiber optical adjustable optical attenuator, a 1x2 fiber coupler, a first photodetector, a fiber optical circulator, a fiber sensing module, a second photodetector, a data acquisition card, a signal demodulation processing unit, and a standard voltage module;

[0012] The laser light source is connected with the fiber optical isolator, the fiber adjustable optical attenuator and the 1x2 fiber coupler in sequence, the 1x2 fiber coupler is connected with the first photoelectric detector and the fiber ring respectively, the fiber ring is connected with the fiber sensing module and the second photoelectric detector respectively, and the second photoelectric detector is connected with the data acquisition card and the signal demodulation processing unit.

[0013] The laser light source is used for emitting a first laser beam, the fiber optical isolator is used for inhibiting the backward reflection of the first laser beam and outputting a second laser beam, the fiber adjustable optical attenuator is used for adjusting the incident power of the second laser beam and outputting a third laser beam, the 1x2 fiber coupler is used for splitting the third laser beam and outputting a fourth laser beam and a fifth laser beam, the first photoelectric detector is used for receiving the fourth laser beam and performing power monitoring, the fiber ring is used for transmitting the fifth laser beam to the fiber sensing module and receiving the reflected light of the fiber sensing module and transmitting the reflected light to the second photoelectric detector, the fiber sensing module is used for reflecting the fifth laser beam by using the fiber core-medium refractive index difference to generate reflected light, the second photoelectric detector is used for converting the reflected light into a voltage signal, the data acquisition card is used for acquiring the voltage signal, the signal demodulation processing unit is used for calculating the sound pressure sensitivity according to a mapping relationship formula between the voltage signal and the sound pressure, and the standard voltage module is used for providing a standard voltage for the data acquisition card.

[0014] Preferably, the power of the fifth laser beam is greater than the power of the fourth laser beam.

[0015] Preferably, the mapping relationship formula between the sound pressure and the reflectivity is as follows:

[0016] ;

[0017] Wherein, p is the sound pressure of the measured sound field, is the refractive index of the fiber core, is the refractive index of the water medium, is a constant with a value of 7.44, is a constant with a value of 295.5MPa, is the standard atmospheric pressure, is the reflectivity in the water medium without the action of the sound field, is the change amount of the reflectivity with the action of the sound field.

[0018] Preferably, the fiber sensing module comprises:

[0019] a fiber sensing end, a fiber core and a fiber end face;

[0020] the fiber end face and the measured sound field are placed in the water medium;

[0021] The water tank is used for placing the water medium, the optical fiber sensing end is used for receiving the fifth laser beam and transmitting to the optical fiber end face through the optical fiber core, the optical fiber end face is used for realizing the mapping of the acoustic wave of the measured acoustic field and the fifth laser beam according to the refractive index difference of the core-medium to obtain reflected light, and the optical fiber core is further used for transmitting the reflected light to the optical fiber sensing end to send to the second photoelectric detector.

[0022] Preferably, the optical fiber sensing end is a single-mode optical fiber after removing the coating layer.

[0023] A self-calibration method of a high-strength optical fiber hydrophone, the method comprising:

[0024] Collecting a voltage signal of the second photoelectric detector;

[0025] Determining a voltage-sound pressure mapping formula according to the voltage signal and the mapping relationship formula of the sound pressure and the reflectivity;

[0026] Using the voltage-sound pressure mapping formula and a standard voltage provided by a standard voltage module to perform sensitivity self-calibration of the optical fiber hydrophone.

[0027] Preferably, the expression of the voltage-sound pressure mapping formula is:

[0028] ;

[0029] Wherein, p is the sound pressure of the measured acoustic field, is the refractive index of the optical fiber core, is the refractive index of the water medium, is a constant with a value of 7.44, is a constant with a value of 295.5 MPa, is the standard atmospheric pressure, is the reflection coefficient, is the output voltage of the second photoelectric detector without the action of the acoustic field, is the change amount of the output voltage of the second photoelectric detector with the action of the acoustic field.

[0030] The present application discloses the following technical effects:

[0031] The present application provides a self-calibration high-strength optical fiber hydrophone based on the end face reflection principle, comprising:

[0032] A laser light source, a fiber optical isolator, a fiber adjustable optical attenuator, a 1x2 fiber coupler, a first photoelectric detector, a fiber optical circulator, a fiber sensing module, a second photoelectric detector, a data acquisition card, a signal demodulation processing unit, a standard voltage module; the laser light source is sequentially connected with the fiber optical isolator, the fiber adjustable optical attenuator and the 1x2 fiber coupler, the 1x2 fiber coupler is connected with the first photoelectric detector and the fiber optical circulator respectively, the fiber optical circulator is connected with the fiber sensing module and the second photoelectric detector respectively, and the second photoelectric detector is connected with the data acquisition card and the signal demodulation processing unit; the laser light source is used for emitting a first laser beam, the fiber optical isolator is used for inhibiting backward reflection of the first laser beam, outputting a second laser beam, the fiber adjustable optical attenuator is used for adjusting incident power of the second laser beam, outputting a third laser beam, the 1x2 fiber coupler is used for splitting the third laser beam, outputting a fourth laser beam and a fifth laser beam, the first photoelectric detector is used for receiving the fourth laser beam and performing power monitoring, the fiber optical circulator is used for transmitting the fifth laser beam to the fiber sensing module and transmitting reflected light of the fiber sensing module to the second photoelectric detector, the fiber sensing module is used for reflecting the fifth laser beam by using fiber core-medium refractive index difference to generate reflected light, and the second photoelectric detector is used for converting the reflected light into a voltage signal, the data acquisition card is used for collecting the voltage signal, the signal demodulation processing unit is used for calculating sound pressure sensitivity according to a mapping relationship formula of the voltage signal and sound pressure, and the standard voltage module is used for providing a standard voltage for the data acquisition card. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0034] Figure 1 A self-calibration high-intensity fiber hydrophone structure schematic diagram based on end face reflection principle is provided for the embodiments of the present application.

[0035] Figure 2 A fiber sensing module structure schematic diagram is provided for the embodiments of the present application.

[0036] Figure 3 A fiber sensing principle schematic diagram based on end face reflection is provided for the embodiments of the present application.

[0037] BRIEF DESCRIPTION OF DRAWINGS

[0038] 1-laser light source, 2-fiber optical isolator, 3-fiber adjustable optical attenuator, 4-fiber coupler, 5-first photodetector, 6-fiber circulator, 7-fiber sensing module, 8-second photodetector, 9-data acquisition card, 10-signal demodulation processing unit, 11-standard voltage module, 12-fiber core, 13-fiber end face, 14-measured acoustic field, 15-water medium, 16-water tank, 17-fiber sensing end. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely 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 work fall within the scope of protection of the present application.

[0040] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0041] As Figure 1 shown, the present application provides a self-calibration high-strength fiber hydrophone based on end face reflection principle, characterized in that it comprises:

[0042] laser light source 1, fiber optical isolator 2, fiber adjustable optical attenuator 3, 1x2 fiber coupler 4, first photodetector 5, fiber circulator 6, fiber sensing module 7, second photodetector 8, data acquisition card 9, signal demodulation processing unit 10, standard voltage module 11;

[0043] The laser light source 1 is connected with the fiber optical isolator 2, fiber adjustable optical attenuator 3 and 1x2 fiber coupler 4 in sequence, the 1x2 fiber coupler 4 is connected with the first photodetector 5 and fiber circulator 6 respectively, the fiber circulator 6 is connected with the fiber sensing module 7 and second photodetector 8 respectively, and the second photodetector 8 is connected with the data acquisition card 9 and signal demodulation processing unit 10;

[0044] The laser source 1 is used to emit a first laser beam, the fiber optical isolator 2 is used to inhibit the back reflection of the first laser beam, output a second laser beam, the fiber tunable optical attenuator 3 is used to adjust the incident power of the second laser beam, output a third laser beam, the 1x2 fiber coupler 4 is used to split the third laser beam, output a fourth laser beam and a fifth laser beam, the first photodetector 5 is used to receive the fourth laser beam and perform power monitoring, the fiber circulator 6 is used to transmit the fifth laser beam to the fiber sensing module 7, and receive the reflected light of the fiber sensing module 7 and transmit it to the second photodetector 8, the fiber sensing module 7 is used to reflect the fifth laser beam by using the fiber core-medium refractive index difference to generate reflected light, the second photodetector 8 is used to convert the reflected light into a voltage signal, the data acquisition card 9 is used to acquire the voltage signal, the signal demodulation processing unit 10 is used to calculate the sound pressure sensitivity according to the voltage signal and the mapping relationship formula of sound pressure and reflectivity, and the standard voltage module 11 is used to provide a standard voltage for the data acquisition card 9.

[0045] The mapping relationship formula of sound pressure and reflectivity is:

[0046] ;

[0047] Wherein, p is the sound pressure of the measured sound field, is the refractive index of the fiber core, is the refractive index of the water medium, is a constant with a value of 7.44, is a constant with a value of 295.5MPa, is the standard atmospheric pressure, is the reflectivity in the water medium without the action of the sound field, is the change amount of reflectivity with the action of the sound field.

[0048] The relationship between reflectivity and voltage is: .

[0049] Further, the power of the fifth laser beam is greater than the power of the fourth laser beam.

[0050] Specifically, the laser source 1 emits a laser beam with stable power, which passes through the fiber optical isolator 2 and the fiber adjustable optical attenuator 3 in turn, and is split by the 1x2 fiber coupler 4, one beam with smaller power is incident to the first photodetector 5 for monitoring the output optical power of the laser source 1, and the other beam with larger power is incident from the first port of the fiber loop mirror 6 as a measurement beam, and is emitted from the second port of the fiber loop mirror 6, the emitted light reaches the fiber end face 13 of the fiber sensing module 7 along the fiber and emits a reflection, the reflected light returns along the original path, is incident from the second port of the fiber loop mirror 6, and is emitted from the third port of the fiber loop mirror 6 and received by the second photodetector 8, when the sound pressure at the fiber end face 13 of the fiber sensing end 17 module changes, the optical power received by the second photodetector 8 also changes correspondingly, the photovoltage signal is collected by the data acquisition card 9, and after demodulation processing by the signal demodulation processing unit 10, the sound pressure measurement is realized; the standard voltage module 11 can output a standard voltage, after replacing the connection between the data acquisition card 9 and the second photodetector 8 with the standard voltage module 11, the calibration of the data acquisition card 9 is realized by comparing the voltage measurement value with the standard voltage. The first photodetector 5 can realize real-time monitoring of the stability of the output optical power of the laser source 1, and is used to feedback and compensate the influence of the change of the optical power of the light source on the sound pressure measurement.

[0051] Further, the fiber sensing module 7 comprises:

[0052] the fiber sensing end 17, the fiber core 12, and the fiber end face 13;

[0053] the fiber end face 13 and the measured sound field 14 are placed in the water medium 15;

[0054] the water tank 16 is used for placing the water medium 15, the fiber sensing end 17 is used for receiving the fifth laser beam and transmitting the fifth laser beam to the fiber end face 13 through the fiber core 12, the fiber end face 13 is used for realizing the mapping of the sound wave of the measured sound field 14 and the fifth laser beam according to the refractive index difference between the core and the medium, so as to obtain reflected light, and the fiber core 12 is also used for transmitting the reflected light to the fiber sensing end 17 to send to the second photodetector 8.

[0055] Specifically, the fiber sensing principle based on end reflection is as follows: Figure 2As shown, including optical fiber sensing end 17, optical fiber core 12, optical fiber end face 13, measured acoustic field 14, water medium 15, water tank 16. Among them, the laser fiber sensing end 17 is generally a single-mode optical fiber after removing the coating layer, the optical fiber end face 13 and the measured acoustic field 14 are placed in the water medium 15, the laser propagates along the optical fiber core 12 to the optical fiber end face 13, and due to the difference in refractive index between the optical fiber core 12 and the water medium 15, the laser exists at the optical fiber end face 13. Transmission and reflection, wherein the reflected light returns along the original path of the optical fiber core 12, and the reflectivity R of the optical fiber end face 13 is directly related to the sound pressure p of the measured acoustic field 14 at this position, that is, R=f(p), and the sound pressure measurement can be realized by measuring the voltage signal output by the second photodetector 8.

[0056] The embodiment also provides a self-calibration method of the high-strength optical fiber hydrophone, and the method comprises:

[0057] Collecting a voltage signal of the second photodetector;

[0058] Determining a voltage-sound pressure mapping formula according to the voltage signal and a mapping relationship formula of the sound pressure and the reflectivity;

[0059] Using the voltage-sound pressure mapping formula and a standard voltage provided by a standard voltage module to perform sensitivity self-calibration of the optical fiber hydrophone.

[0060] Specifically, the reusable characteristics and the self-calibration principle of the optical fiber hydrophone are as follows:

[0061] The physical action path of the sound pressure to the output voltage of the photodetector is: sound pressure→water medium density→water medium refractive index→interface reflectivity→reflected light optical power→photodetector output voltage. According to the Tate equation, the Gradstondale relationship equation, the Fresnel theorem and the photovoltage conversion relationship of the detector in fluid mechanics, the relationship (voltage-sound pressure mapping formula) between the sound pressure p and the output voltage change rate of the photodetector can be derived as follows:

[0062] (1)

[0063] Among them, p is the sound pressure of the measured acoustic field, is the refractive index of the optical fiber core, is the refractive index of the water medium, is a constant with a value of 7.44, is a constant with a value of 295.5 MPa, is the standard atmospheric pressure, is the reflection coefficient, is the output voltage of the second photodetector without the action of the sound field, is the output voltage change of the second photodetector with the action of the sound field.

[0064] Specifically, is a variable related to the truncation of the fiber end face, the stray light received by the photodetector, and the photoelectric conversion coefficient of the photodetector; , , , , is a constant term related to the refractive index of the fiber core, the refractive index and density of the water medium under normal pressure, which has no effect on subsequent measurement results after being determined. Therefore, the value of is determined by measuring the voltage, that is, the mapping relationship between the output voltage of the photodetector and the measured sound pressure. Further, the sensitivity of the fiber hydrophone is traced to the standard voltage module to realize self-calibration of the sensitivity.

[0065] Moreover, the sensitive element of the hydrophone is only the fiber end face, and its structure is very simple, and even if it is damaged, it can be reacquired through the common fiber cutting operation in the field. Considering that there will be certain differences in the condition of the fiber end face after each cutting, therefore, the sensitivity of the hydrophone needs to be self-calibrated through the above-mentioned voltage measurement before the sound pressure measurement can continue.

[0066] Since the sensitivity of the hydrophone depends on the corresponding relationship between the output voltage of the photodetector and the measured sound pressure, according to formula (1), the value of can be determined by measuring the voltage, that is, the self-calibration of the sensitivity can be realized. The value of Figure 3 depends on the three voltage values output by the second photodetector 8. The specific principle of the self-calibration process is shown in O When the fiber end face is placed in the water medium, the photoelectric voltage U B output by the second photodetector is composed of three parts: the dark voltage U S output by the photodetector, the photoelectric voltage U R caused by the stray light in the optical path, and the photoelectric voltage U S caused by the reflected light of the fiber end face, and has the following relationship:

[0067] (2)

[0068] The key to realizing the self-calibration of the sensitivity of the hydrophone is to obtain the photoelectric voltage U R caused by the stray light in the optical path and the photoelectric voltage U O caused by the reflected light of the fiber end face. U B can be directly obtained by measuring the output voltage of the second photodetector when the fiber end face is placed in the water medium. U RThe value of the fiber end face can be placed in the refractive index matching liquid medium, which can be a certain concentration of sucrose solution or glycerol solution, and the refractive index is the same as that of the fiber core. At this time, the reflectivity of the laser at the fiber end face is zero, and the photoelectric voltage output by the second photodetector is recorded as U M Therefore, we have:

[0069] (3)

[0070] Further, the value of U can be obtained according to formulas (1) and (2) S The value of U is:

[0071] (4)

[0072] U can be expressed as:

[0073] (5)

[0074] Therefore, by measuring the voltage output of the second photodetector when the fiber end face is in water and the refractive index matching liquid medium, and the dark voltage of the second photodetector, the value of U can be obtained, and then the relationship between the sound pressure and the output voltage of the photodetector is obtained by formula (1):

[0075] (6)

[0076] According to formula (6), the voltage signal collected by the data acquisition card can be used to calculate the sound pressure sensitivity of the fiber hydrophone by using the signal demodulation processing unit, and the sensitivity can be traced to the standard voltage module through voltage measurement, thereby realizing the self-calibration of the sensitivity of the fiber hydrophone.

[0077] where p is the sound pressure of the measured sound field, is the refractive index of the fiber core, is the refractive index of the water medium, is a constant with a value of 7.44, is a constant with a value of 295.5 MPa, is the standard atmospheric pressure, is the reflectivity in the water medium without sound field action, is the change amount of reflectivity with sound field action.

[0078] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between each embodiment can be referred to each other.

[0079] ​The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A self-calibrating high-strength fiber-optic hydrophone based on the principle of end-face reflection, characterized in that, It comprises: a laser light source, a fiber optical isolator, a fiber adjustable optical attenuator, a 1x2 fiber coupler, a first photodetector, a fiber optical circulator, a fiber sensing module, a second photodetector, a data acquisition card, a signal demodulation processing unit, and a standard voltage module; the laser light source is connected with the fiber optical isolator, the fiber adjustable optical attenuator, and the 1x2 fiber coupler in sequence, the 1x2 fiber coupler is connected with the first photodetector and the fiber optical circulator respectively, the fiber optical circulator is connected with the fiber sensing module and the second photodetector respectively, and the second photodetector is connected with the data acquisition card and the signal demodulation processing unit; the laser light source is used for emitting a first laser beam, the fiber optical isolator is used for suppressing backward reflection of the first laser beam, outputting a second laser beam, the fiber adjustable optical attenuator is used for adjusting incident power of the second laser beam, outputting a third laser beam, the 1x2 fiber coupler is used for splitting the third laser beam, outputting a fourth laser beam and a fifth laser beam, the first photodetector is used for receiving the fourth laser beam and performing power monitoring, the fiber optical circulator is used for transmitting the fifth laser beam to the fiber sensing module and receiving reflected light of the fiber sensing module to the second photodetector, the fiber sensing module is used for reflecting the fifth laser beam by using a fiber core-medium refractive index difference to generate reflected light, and the second photodetector is used for converting the reflected light into a voltage signal, the data acquisition card is used for collecting the voltage signal, the signal demodulation processing unit is used for calculating sound pressure sensitivity according to a mapping relationship formula of the voltage signal and sound pressure, and the standard voltage module is used for providing a standard voltage for the data acquisition card.

2. A self-calibrating high intensity fiber hydrophone based on end-face reflection principle according to claim 1, characterized in that, The power of the fifth laser beam is greater than the power of the fourth laser beam.

3. A self-calibrating high intensity fiber hydrophone based on end-face reflection principle according to claim 1, characterized in that, The mapping relationship formula of the sound pressure and the reflectivity is: ； where p is the sound pressure of the sound field being measured, n is the refractive index of the optical fiber core, n is the refractive index of the water medium, C is a constant with a value of 7.44, C is a constant with a value of 295.5 MPa, P is the standard atmospheric pressure, R is the reflectance in the water medium when there is no sound field, ΔR is the change in reflectance when there is a sound field.

4. A self-calibrating high intensity fiber hydrophone based on end-face reflection principle according to claim 1, characterized in that, The fiber sensing module comprises: a fiber sensing end, a fiber core, and a fiber end face; the fiber end face and the measured sound field are placed in a water medium; the fiber sensing end is used for receiving the fifth laser beam and transmitting the fifth laser beam to the fiber end face through the fiber core, the fiber end face is used for obtaining reflected light according to a fiber core-medium refractive index difference, realizing mapping of the sound pressure of the measured sound field and the reflected light, and the fiber core is further used for transmitting the reflected light to the fiber sensing end to send to the second photodetector.

5. A self-calibrating high-strength fiber-optic hydrophone based on the principle of end-face reflection according to claim 4, characterized in that, The fiber sensing end is a single-mode fiber after removing a coating layer.

6. A self-calibration method of a high strength fiber optic hydrophone, applied to the fiber optic hydrophone of any one of claims 1 to 5, characterized in that, The method comprises: collecting a voltage signal of the second photodetector; determining a voltage-sound pressure mapping formula according to the voltage signal and the mapping relationship formula of the sound pressure and the reflectivity; performing sensitivity self-calibration of the fiber hydrophone by using the voltage-sound pressure mapping formula and a standard voltage provided by the standard voltage module.

7. A method of self-calibration of a high-strength fiber-optic hydrophone according to claim 6, characterized in that, The expression of the voltage-sound pressure mapping formula is: ； wherein p is the sound pressure of the sound field being measured, n is the refractive index of the optical fiber core, n is the refractive index of the water medium, C is a constant with a value of 7.44, C is a constant with a value of 295.5 MPa, P is the standard atmospheric pressure, R is the reflection coefficient, V0 is the output voltage of the second photodetector when there is no sound field, ΔV is the change in the output voltage of the second photodetector when there is a sound field.

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