Ultra-sensitive underwater acoustic sensor based on resonant cavity packaging structure and measuring method

Abstract

The invention relates to an optical microcavity underwater acoustic sensor, in particular to an ultra-sensitive underwater acoustic sensor based on a resonant cavity packaging structure and a measuring method. The sensor comprises a 1630 nm laser, a first isolator, a first polarization controller, a 1550 nm laser, a second isolator, a second polarization controller, a phase modulator, a resonant cavity packaging structure, a long pass filter, a photoelectric detector, an oscilloscope and a computer. The resonant cavity packaging structure comprises a packaging base. A groove is formed in the surface of the packaging base; two notches are formed in the groove wall of the groove; a conical optical fiber penetrates through the two notches; a crystal resonant cavity is arranged in the groove, and the crystal resonant cavity is coupled with the conical optical fiber; the groove and the two notches are jointly filled with a packaging adhesive layer, and the packaging adhesive layer wraps the conical optical fiber and the crystal resonant cavity at the same time. The problems that an existing optical microcavity underwater acoustic sensor is low in sensitivity and poor in stability are solved, and the optical microcavity underwater acoustic sensor is suitable for the fields of underwater target monitoring, seabed resource exploration, underwater acoustic communication and the like.

Description

Technical Field

[0001] The present invention relates to an optical microcavity underwater acoustic sensor, in particular to an ultrasensitive underwater acoustic sensor based on a resonant cavity encapsulation structure and a measurement method therefor. Background Art

[0002] When sound waves propagate underwater, they have small energy attenuation and long transmission distance, and have become an important means for underwater target monitoring, seabed resource exploration, and underwater acoustic communication. As the core of the above applications, optical microcavity underwater acoustic sensors have become a current research hotspot. Under the existing technical conditions, optical microcavity underwater acoustic sensors generally work based on F-P resonant cavities or waveguide resonant cavities. However, in practical applications, the existing optical microcavity underwater acoustic sensors have the following problems: First, due to the low quality factors of F-P resonant cavities and waveguide resonant cavities, the existing optical microcavity underwater acoustic sensors have the problem of low sensitivity. Second, due to the poor pressure and temperature resistance performance of F-P resonant cavities and waveguide resonant cavities, the existing optical microcavity underwater acoustic sensors have the problem of poor stability. Based on this, it is necessary to invent an ultrasensitive underwater acoustic sensor based on a resonant cavity encapsulation structure and a measurement method therefor to solve the problems of low sensitivity and poor stability of the existing optical microcavity underwater acoustic sensors. Summary of the Invention

[0003] In order to solve the problems of low sensitivity and poor stability of the existing optical microcavity underwater acoustic sensors, the present invention provides an ultrasensitive underwater acoustic sensor based on a resonant cavity encapsulation structure and a measurement method therefor.

[0004] The present invention is implemented by adopting the following technical solutions:

[0005] An ultrasensitive underwater acoustic sensor based on a resonant cavity encapsulation structure includes a 1630 nm laser, a first isolator, a first polarization controller, a 1550 nm laser, a second isolator, a second polarization controller, a phase modulator, a resonant cavity encapsulation structure, a long-pass filter, a photodetector, an oscilloscope, and a computer;

[0006] The resonant cavity encapsulation structure includes a packaging base; a groove is formed on the surface of the packaging base; two notches are formed on the groove wall of the groove; a tapered optical fiber penetrates through the two notches together; a crystal resonant cavity is arranged in the groove, and the crystal resonant cavity is coupled with the tapered optical fiber; a packaging adhesive layer is filled in the groove and the two notches together, and the packaging adhesive layer simultaneously coats the tapered optical fiber and the crystal resonant cavity;

[0007] The output end of the 1630 nm laser is connected to the input end of the phase modulator through a first isolator and a first polarization controller in sequence; the output end of the 1550 nm laser is connected to the input end of the phase modulator through a second isolator and a second polarization controller in sequence; the output end of the phase modulator is connected to the input end of the photodetector through a tapered fiber and a long-pass filter in sequence; the signal output end of the photodetector is connected to the signal input end of the computer through an oscilloscope.

[0008] It further includes a signal generator, a power amplifier, a transducer, and a standard hydrophone; the signal output end of the signal generator is connected to the signal input end of the transducer through the power amplifier; the signal output end of the standard hydrophone is connected to the signal input end of the oscilloscope; both the transducer and the standard hydrophone are located beside the resonant cavity packaging structure.

[0009] It further includes a lock-in amplifier and a PID controller; the signal output end of the photodetector is connected to the modulation end of the 1550 nm laser through the lock-in amplifier and the PID controller in sequence.

[0010] Both the 1630 nm laser and the 1550 nm laser adopt continuously tunable narrowband lasers; the encapsulation adhesive layer is made of MY133 ultraviolet curable adhesive with low Young's modulus and low refractive index.

[0011] A super-sensitive underwater acoustic measurement method based on a resonant cavity packaging structure, which is realized based on a super-sensitive underwater acoustic sensor of the present invention, and the method is realized by the following steps:

[0012] First, place the resonant cavity packaging structure underwater and control the sensor to enter the working mode; the working mode is specifically:

[0013] The 1550 nm laser emits pump light in the 1550 nm band, and the pump light sequentially passes through the second isolator, the second polarization controller, the phase modulator, the tapered fiber, the crystal resonant cavity, the tapered fiber and is incident on the long-pass filter, and is absorbed by the long-pass filter; when the pump light passes through the crystal resonant cavity, the pump light excites the Raman gain of the crystal resonant cavity, thereby compensating for the material loss of the crystal resonant cavity, so as to improve the quality factor of the crystal resonant cavity; at the same time, the 1630 nm laser emits probe light in the 1630 nm band, and the probe light sequentially passes through the first isolator, the first polarization controller, the phase modulator, the tapered fiber, the crystal resonant cavity, the tapered fiber, the long-pass filter and is incident on the photodetector, and then is converted into an electrical signal by the photodetector; the electrical signal is transmitted to the oscilloscope and is converted into a resonance spectrum by the oscilloscope; the resonance spectrum is displayed on the oscilloscope on the one hand and transmitted to the computer on the other hand.

[0014] In the working mode, when an underwater acoustic signal acts on the crystal resonator cavity, the voltage at the resonant wavelength of the resonance spectrum changes; the computer monitors the voltage change in real time and substitutes the voltage change into the underwater acoustic pressure measurement equation of the sensor, and thus calculates the underwater acoustic pressure; the underwater acoustic pressure measurement equation of the sensor is expressed as follows:

[0015]

[0016] In the formula: ΔV represents the voltage change; P represents the underwater acoustic pressure; λ represents the resonant wavelength of the resonance spectrum; represents the change rate of the radius of the crystal resonator cavity; represents the change rate of the refractive index of the crystal resonator cavity; represents the slope of the linear region of the first derivative of the resonance spectrum; λ, are all known quantities.

[0017] This method further includes using a signal generator, a power amplifier, a transducer, and a standard hydrophone to determine whether the performance indicators of the sensor meet the requirements and calculate the sensitivity level of the sensor; the specific steps are as follows:

[0018] First, place the resonator cavity packaging structure, the transducer, and the standard hydrophone underwater and control the sensor to enter the working mode;

[0019] In the working mode, the signal generator outputs a sine wave signal, the sine wave signal is transmitted to the transducer through the power amplifier, and is converted into an underwater acoustic signal by the transducer; the underwater acoustic signal acts on the crystal resonator cavity on the one hand, causing the voltage at the resonant wavelength of the resonance spectrum to change, and on the other hand acts on the standard hydrophone; the computer monitors the voltage change in real time; the standard hydrophone monitors the underwater acoustic pressure in real time;

[0020] Then, on the one hand, calculate the sensitivity test value of the sensor according to the voltage change and the underwater acoustic pressure, and on the other hand, calculate the sensitivity standard value of the sensor; the specific calculation formulas are as follows:

[0021]

[0022] In the formula: S1 represents the sensitivity test value of the sensor; S2 represents the sensitivity standard value of the sensor; ΔV represents the voltage change; P represents the underwater acoustic pressure; λ represents the resonant wavelength of the resonance spectrum; represents the change rate of the radius of the crystal resonator cavity; represents the change rate of the refractive index of the crystal resonator cavity; represents the slope of the linear region of the first derivative of the resonance spectrum; λ, are all known quantities;

[0023] Then, compare the sensitivity test value of the sensor with the sensitivity standard value of the sensor, and judge whether the performance index of the sensor meets the requirements according to the comparison result: If the sensitivity test value of the sensor coincides with the sensitivity standard value of the sensor, it indicates that the performance index of the sensor meets the requirements; if the sensitivity test value of the sensor does not coincide with the sensitivity standard value of the sensor, it indicates that the performance index of the sensor does not meet the requirements.

[0024] Then, calculate the sensitivity level of the sensor according to the sensitivity test value of the sensor and the underwater reference sensitivity; the specific calculation formula is as follows:

[0025]

[0026] In the formula: M represents the sensitivity level of the sensor, and its unit is dB; S1 represents the sensitivity test value of the sensor, and its unit is 1V / Pa; S r represents the underwater reference sensitivity, and its unit is 1V / μPa.

[0027] This method also includes using a lock-in amplifier and a PID controller to achieve frequency tracking and locking of the 1550nm laser; the specific steps are as follows:

[0028] In the working mode, the electrical signal is synchronously demodulated by the lock-in amplifier and then transmitted to the PID controller; the PID controller adjusts the output frequency of the 1550nm laser in real time according to the demodulation result, so that the output frequency of the 1550nm laser is consistent with the resonance frequency of the crystal resonator, thereby achieving frequency tracking and locking of the 1550nm laser.

[0029] Compared with the existing optical microcavity underwater acoustic sensor, the present invention no longer works based on the F-P resonator or the waveguide resonator, but works based on the resonator packaging structure, and thus has the following advantages: First, since the crystal resonator in the resonator packaging structure has an ultra-high quality factor and an extremely small mode volume, the present invention has ultra-high sensitivity. On this basis, the present invention uses Raman gain to compensate for the material loss of the crystal resonator, so that the quality factor of the crystal resonator is further improved, and thus the sensitivity of the present invention is further improved. Second, since the resonator packaging structure has good pressure and temperature resistance (the pressure resistance can reach 1MPa, and the temperature resistance can reach 150°C), the present invention has good stability.

[0030] The present invention effectively solves the problems of low sensitivity and poor stability of the existing optical microcavity underwater acoustic sensor, and is applicable to fields such as underwater target monitoring, seabed resource exploration, and underwater acoustic communication. Brief Description of the Drawings

[0031] Figure 1 is a schematic structural diagram of the present invention.

[0032] Figure 2 It is a schematic structural diagram of the resonant cavity packaging structure in the present invention.

[0033] Figure 3 is Figure 2 the rear view of.

[0034] Figure 4 is Figure 2 a partial structural schematic diagram of.

[0035] Figure 5 is Figure 4 a partial structural schematic Figure 1 .

[0036] Figure 6 is Figure 5 the A-A cross-sectional view of.

[0037] Figure 7 is Figure 5 the B-B cross-sectional view of.

[0038] Figure 8 is Figure 4 a partial structural schematic Figure 2 .

[0039] In the figure: 1 - 1630nm laser, 2 - first isolator, 3 - first polarization controller, 4 - 1550nm laser, 5 - second isolator, 6 - second polarization controller, 7 - phase modulator, 8.1 - packaging base, 8.2 - tapered optical fiber, 8.3 - crystal resonant cavity, 8.4 - packaging adhesive layer, 9 - long-pass filter, 10 - photodetector, 11 - oscilloscope, 12 - computer, 13 - signal generator, 14 - power amplifier, 15 - transducer, 16 - standard hydrophone, 17 - lock-in amplifier, 18 - PID controller. Specific embodiments

[0040] A super-sensitive underwater acoustic sensor based on a resonant cavity packaging structure, comprising a 1630nm laser 1, a first isolator 2, a first polarization controller 3, a 1550nm laser 4, a second isolator 5, a second polarization controller 6, a phase modulator 7, a resonant cavity packaging structure, a long-pass filter 9, a photodetector 10, an oscilloscope 11, and a computer 12;

[0041] The resonant cavity packaging structure includes a packaging base 8.1; a groove is formed on the surface of the packaging base 8.1; two notches are formed on the groove wall of the groove; a tapered optical fiber 8.2 penetrates through the two notches together; a crystal resonant cavity 8.3 is arranged in the groove, and the crystal resonant cavity 8.3 is coupled with the tapered optical fiber 8.2; a packaging adhesive layer 8.4 is filled in the groove and the two notches together, and the packaging adhesive layer 8.4 covers the tapered optical fiber 8.2 and the crystal resonant cavity 8.3 at the same time;

[0042] The output end of the 1630 nm laser 1 is sequentially connected to the input end of the phase modulator 7 through a first isolator 2 and a first polarization controller 3; the output end of the 1550 nm laser 4 is sequentially connected to the input end of the phase modulator 7 through a second isolator 5 and a second polarization controller 6; the output end of the phase modulator 7 is sequentially connected to the input end of the photodetector 10 through a tapered optical fiber 8.2 and a long-pass filter 9; the signal output end of the photodetector 10 is connected to the signal input end of the computer 12 through an oscilloscope 11.

[0043] It further includes a signal generator 13, a power amplifier 14, a transducer 15, and a standard hydrophone 16; the signal output end of the signal generator 13 is connected to the signal input end of the transducer 15 through the power amplifier 14; the signal output end of the standard hydrophone 16 is connected to the signal input end of the oscilloscope 11; both the transducer 15 and the standard hydrophone 16 are located beside the resonant cavity packaging structure.

[0044] It further includes a lock-in amplifier 17 and a PID controller 18; the signal output end of the photodetector 10 is sequentially connected to the modulation end of the 1550 nm laser 4 through the lock-in amplifier 17 and the PID controller 18.

[0045] Both the 1630 nm laser 1 and the 1550 nm laser 4 adopt continuously tunable narrowband lasers; the packaging adhesive layer 8.4 is made of MY133 ultraviolet curing glue with low Young's modulus and low refractive index.

[0046] A super-sensitive underwater acoustic measurement method based on a resonant cavity packaging structure, this method is realized based on a super-sensitive underwater acoustic sensor of the present invention, and this method is realized by the following steps:

[0047] First, place the resonant cavity packaging structure underwater and control the sensor to enter the working mode; the working mode is specifically:

[0048] The 1550nm laser 4 emits pump light in the 1550nm band. The pump light sequentially passes through the second isolator 5, the second polarization controller 6, the phase modulator 7, the tapered fiber 8.2, the crystal resonator 8.3, the tapered fiber 8.2 and is incident on the long-pass filter 9, and is absorbed by the long-pass filter 9. When the pump light passes through the crystal resonator 8.3, the pump light excites the Raman gain of the crystal resonator 8.3, thereby compensating for the material loss of the crystal resonator 8.3, and thus improving the quality factor of the crystal resonator 8.3. At the same time, the 1630nm laser 1 emits probe light in the 1630nm band. The probe light sequentially passes through the first isolator 2, the first polarization controller 3, the phase modulator 7, the tapered fiber 8.2, the crystal resonator 8.3, the tapered fiber 8.2, the long-pass filter 9 and is incident on the photodetector 10, and then is converted into an electrical signal by the photodetector 10. The electrical signal is transmitted to the oscilloscope 11 and is converted into a resonance spectrum by the oscilloscope 11. The resonance spectrum is displayed on the oscilloscope 11 on the one hand and transmitted to the computer 12 on the other hand;

[0049] In the working mode, when the underwater acoustic signal acts on the crystal resonator 8.3, the voltage at the resonance wavelength of the resonance spectrum changes. The computer 12 monitors the voltage change in real time and substitutes the voltage change into the underwater acoustic pressure measurement equation of the sensor, thereby calculating the underwater acoustic pressure. The underwater acoustic pressure measurement equation of the sensor is expressed as follows:

[0050]

[0051] Where: ΔV represents the voltage change; P represents the underwater acoustic pressure; λ represents the resonance wavelength of the resonance spectrum; represents the change rate of the radius of the crystal resonator 8.3; represents the change rate of the refractive index of the crystal resonator 8.3; represents the slope of the linear region of the first derivative of the resonance spectrum; λ, are all known quantities.

[0052] This method further includes using the signal generator 13, the power amplifier 14, the transducer 15, and the standard hydrophone 16 to determine whether the performance indicators of the sensor meet the requirements and calculate the sensitivity level of the sensor. The specific steps are as follows:

[0053] First, place the resonator packaging structure, the transducer 15, and the standard hydrophone 16 underwater and control the sensor to enter the working mode;

[0054] In the working mode, the signal generator 13 outputs a sine wave signal, which is transmitted to the transducer 15 through the power amplifier 14 and converted into an underwater acoustic signal by the transducer 15. On the one hand, the underwater acoustic signal acts on the crystal resonator cavity 8.3, causing the voltage at the resonant wavelength of the resonant spectrum to change. On the other hand, it acts on the standard hydrophone 16. The computer 12 monitors the voltage change in real time; the standard hydrophone 16 monitors the underwater acoustic pressure in real time.

[0055] Then, on the one hand, the sensitivity test value of the sensor is calculated based on the voltage change and the underwater acoustic pressure, and on the other hand, the sensitivity standard value of the sensor is calculated. The specific calculation formula is as follows:

[0056]

[0057] In the formula: S1 represents the sensitivity test value of the sensor; S2 represents the sensitivity standard value of the sensor; ΔV represents the voltage change; P represents the underwater acoustic pressure; λ represents the resonant wavelength of the resonant spectrum. represents the change rate of the radius of the crystal resonator cavity 8.3; represents the change rate of the refractive index of the crystal resonator cavity 8.3; represents the slope of the first derivative linear region of the resonant spectrum; λ, are all known quantities;

[0058] Then, the sensitivity test value of the sensor is compared with the sensitivity standard value of the sensor, and the performance index of the sensor is judged according to the comparison result: if the sensitivity test value of the sensor coincides with the sensitivity standard value of the sensor, it indicates that the performance index of the sensor meets the requirements; if the sensitivity test value of the sensor does not coincide with the sensitivity standard value of the sensor, it indicates that the performance index of the sensor does not meet the requirements.

[0059] Then, the sensitivity level of the sensor is calculated based on the sensitivity test value of the sensor and the underwater reference sensitivity. The specific calculation formula is as follows:

[0060]

[0061] In the formula: M represents the sensitivity level of the sensor, and its unit is dB; S1 represents the sensitivity test value of the sensor, and its unit is 1V / Pa; S r represents the underwater reference sensitivity, and its unit is 1V / μPa.

[0062] This method also includes using the lock-in amplifier 17 and the PID controller 18 to achieve the frequency tracking and locking of the 1550nm laser 4. The specific steps are as follows:

[0063] In the working mode, the electrical signal is synchronously demodulated by the lock-in amplifier 17 and then transmitted to the PID controller 18; the PID controller 18 adjusts the output frequency of the 1550nm laser 4 in real time according to the demodulation result, so that the output frequency of the 1550nm laser 4 is consistent with the resonance frequency of the crystal resonator 8.3, thereby realizing the frequency tracking and locking of the 1550nm laser 4.

[0064] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and the protection scope of the present invention is defined by the appended claims. Without departing from the principle and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. An ultrasensitive underwater acoustic sensor based on a resonant cavity encapsulation structure, characterized in that: It includes a 1630 nm laser (1), a first isolator (2), a first polarization controller (3), a 1550 nm laser (4), a second isolator (5), a second polarization controller (6), a phase modulator (7), a resonant cavity packaging structure, a long-pass filter (9), a photodetector (10), an oscilloscope (11), and a computer (12); The resonant cavity packaging structure includes a packaging base (8.1); a groove is formed on the surface of the packaging base (8.1); two notches are formed on the groove wall of the groove; a tapered optical fiber (8.2) penetrates through the two notches together; a crystal resonant cavity (8.3) is arranged in the groove, and the crystal resonant cavity (8.3) is coupled with the tapered optical fiber (8.2); a packaging glue layer (8.4) is potted in the groove and the two notches together, and the packaging glue layer (8.4) covers the tapered optical fiber (8.2) and the crystal resonant cavity (8.3) at the same time; The output end of the 1630 nm laser (1) is sequentially connected to the input end of the phase modulator (7) through the first isolator (2) and the first polarization controller (3); the output end of the 1550 nm laser (4) is sequentially connected to the input end of the phase modulator (7) through the second isolator (5) and the second polarization controller (6); the output end of the phase modulator (7) is sequentially connected to the input end of the photodetector (10) through the tapered optical fiber (8.2) and the long-pass filter (9); the signal output end of the photodetector (10) is connected to the signal input end of the computer (12) through the oscilloscope (11).

2. The ultrasensitive underwater acoustic sensor based on the resonant cavity packaging structure according to claim 1, wherein: It further includes a signal generator (13), a power amplifier (14), a transducer (15), and a standard hydrophone (16); the signal output end of the signal generator (13) is connected to the signal input end of the transducer (15) through the power amplifier (14); the signal output end of the standard hydrophone (16) is connected to the signal input end of the oscilloscope (11); both the transducer (15) and the standard hydrophone (16) are located beside the resonant cavity packaging structure.

3. The ultrasensitive underwater acoustic sensor based on the resonant cavity packaging structure according to claim 1, wherein: It further includes a lock-in amplifier (17) and a PID controller (18); the signal output end of the photodetector (10) is sequentially connected to the modulation end of the 1550 nm laser (4) through the lock-in amplifier (17) and the PID controller (18).

4. The ultra-sensitive underwater acoustic sensor based on the resonant cavity packaging structure according to claim 1, wherein: Both the 1630 nm laser (1) and the 1550 nm laser (4) adopt continuously tunable narrowband lasers; the packaging glue layer (8.4) is made of MY133 ultraviolet curing glue with low Young's modulus and low refractive index.

5. A super-sensitive underwater acoustic measurement method based on a resonant cavity encapsulation structure, which is implemented based on a super-sensitive underwater acoustic sensor with a resonant cavity encapsulation structure as described in claim 1, and is characterized in that: This method is realized by the following steps: First, place the resonant cavity packaging structure underwater and control the sensor to enter the working mode; the working mode is specifically: The 1550 nm laser (4) emits pump light in the 1550 nm band. The pump light is incident on the long-pass filter (9) successively through the second isolator (5), the second polarization controller (6), the phase modulator (7), the tapered fiber (8.2), the crystal resonator (8.3), and the tapered fiber (8.2), and is absorbed by the long-pass filter (9). When the pump light passes through the crystal resonator (8.3), the pump light excites the Raman gain of the crystal resonator (8.3), thereby compensating for the material loss of the crystal resonator (8.3), and thus improving the quality factor of the crystal resonator (8.3). At the same time, the 1630 nm laser (1) emits probe light in the 1630 nm band. The probe light is incident on the photodetector (10) successively through the first isolator (2), the first polarization controller (3), the phase modulator (7), the tapered fiber (8.2), the crystal resonator (8.3), the tapered fiber (8.2), and the long-pass filter (9), and is then converted into an electrical signal by the photodetector (10). The electrical signal is transmitted to the oscilloscope (11) and is converted into a resonance spectrum by the oscilloscope (11). The resonance spectrum is displayed on the oscilloscope (11) on the one hand and transmitted to the computer (12) on the other hand. In the working mode, when the underwater acoustic signal acts on the crystal resonator (8.3), the voltage at the resonance wavelength of the resonance spectrum changes. The computer (12) monitors the voltage change in real time and substitutes the voltage change into the underwater acoustic pressure measurement equation of the sensor, thereby calculating the underwater acoustic pressure. The underwater acoustic pressure measurement equation of the sensor is expressed as follows: Where: ΔV represents the voltage change; P represents the underwater sound pressure; λ represents the resonance wavelength of the resonance spectrum; represents the change rate of the radius of the crystal resonator (8.3); represents the change rate of the refractive index of the crystal resonator (8.3); represents the slope of the linear region of the first derivative of the resonance spectrum; λ, are all known quantities.

6. The ultrasensitive underwater acoustic measurement method based on a resonant cavity packaging structure according to claim 5, characterized in that: This method further includes using a signal generator (13), a power amplifier (14), a transducer (15), and a standard hydrophone (16) to determine whether the performance indicators of the sensor meet the requirements and calculate the sensitivity level of the sensor. The specific steps are as follows: First, place the resonator packaging structure, the transducer (15), and the standard hydrophone (16) underwater and control the sensor to enter the working mode. In the working mode, the signal generator (13) outputs a sine wave signal. The sine wave signal is transmitted to the transducer (15) through the power amplifier (14) and is converted into an underwater acoustic signal by the transducer (15). The underwater acoustic signal acts on the crystal resonator (8.3) on the one hand, causing the voltage at the resonance wavelength of the resonance spectrum to change, and acts on the standard hydrophone (16) on the other hand. The computer (12) monitors the voltage change in real time. The standard hydrophone (16) monitors the underwater acoustic pressure in real time. Then, on the one hand, calculate the sensitivity test value of the sensor based on the voltage change and the underwater acoustic pressure, and on the other hand, calculate the sensitivity standard value of the sensor. The specific calculation formulas are as follows: Where: S1 represents the sensitivity test value of the sensor; S2 represents the sensitivity standard value of the sensor; ΔV represents the voltage change; P represents the underwater sound pressure; λ represents the resonance wavelength of the resonance spectrum; represents the change rate of the radius of the crystal resonator (8.3); represents the change rate of the refractive index of the crystal resonator (8.3); represents the slope of the linear region of the first derivative of the resonance spectrum; λ, are all known quantities; Then, compare the sensitivity test value of the sensor with the sensitivity standard value of the sensor, and judge whether the performance indicators of the sensor meet the requirements according to the comparison result: If the sensitivity test value of the sensor coincides with the sensitivity standard value of the sensor, it indicates that the performance indicators of the sensor meet the requirements; if the sensitivity test value of the sensor does not coincide with the sensitivity standard value of the sensor, it indicates that the performance indicators of the sensor do not meet the requirements. Then, the sensitivity level of the sensor is calculated based on the sensitivity test value of the sensor and the underwater reference sensitivity; the specific calculation formula is as follows: Where: M represents the sensitivity level of the sensor, with the unit of dB; S1 represents the measured value of the sensor sensitivity, with the unit of 1V / Pa; S r represents the underwater reference sensitivity, with the unit of 1V / μPa.

7. A super-sensitive underwater acoustic measurement method based on a resonant cavity packaging structure according to claim 5, characterized in that: This method further includes using a lock-in amplifier (17) and a PID controller (18) to achieve frequency tracking and locking of the 1550 nm laser (4); the specific steps are as follows: In the working mode, the electrical signal is synchronously demodulated by the lock-in amplifier (17) and then transmitted to the PID controller (18); the PID controller (18) adjusts the output frequency of the 1550 nm laser (4) in real time according to the demodulation result, so that the output frequency of the 1550 nm laser (4) is consistent with the resonance frequency of the crystal resonator (8.3), thereby achieving frequency tracking and locking of the 1550 nm laser (4).

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