Sensing system and method for dual-parameter measurement of static pressure and sound pressure based on Fabry-Perot etalon

Abstract

The present invention belongs to the field of optical fiber sensing technology, and proposes a sensing system and method for dual-parameter measurement of static pressure and sound pressure based on a Fabry-Perot etalon, so as to realize high-speed demodulation of sensors in an environment where low-frequency static pressure with a large dynamic range and high-frequency perturbation sound pressure coexist. The system includes a VT-DBR laser with a wide tunable range, an optical fiber Fabry-Perot etalon, a detector, and a corresponding static pressure and sound pressure demodulation algorithm; the present invention adopts a wide tunable laser to simplify the system complexity of low-frequency static pressure and high-frequency perturbation sound pressure measurement, and reduce the overall cost. The optical fiber Fabry-Perot standard that does not involve mechanical deformation of the diaphragm has a good frequency response and a large dynamic range; the white light interference signal processing algorithm and the fixed working point algorithm are used to realize the measurement of low-frequency static pressure and high-frequency perturbation sound pressure. The present invention can be applied to typical applications such as aviation acoustics and turbine engines where dynamic sound pressure and static pressure both need to be quickly detected.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to a sensing system and method for measuring dual parameters of static pressure and sound pressure based on a Fabry-Perot etalon. Background Art

[0002] Fabry-Perot interferometry (FPI) fiber optic sensors can be designed in a variety of acoustic pressure-sensitive configurations. Due to their compact size, high sensitivity, and resistance to electromagnetic interference, they are widely used in monitoring parameters such as pressure and sound. They are a representative example of fiber optic sensing technology, playing an important role in industrial manufacturing, medical testing, aerospace, and other fields. As the application of FPI sensors expands, measuring high-frequency acoustic pressure signals under high static pressure has become a bottleneck in their application. Currently, diaphragm-type extrinsic Fabry-Perot interferometry (EFPI) fiber optic pressure sensors are more common. They sense pressure parameters by detecting changes in the Fabry-Perot cavity length caused by compressive deformation of the diaphragm. However, because this type of sensor primarily relies on the mechanical deformation of the diaphragm to achieve measurement performance, performance indicators such as sensitivity, resolution, and dynamic range are often limited by parameters such as the diaphragm material, thickness, and radius. On the other hand, in typical applications such as aeroacoustics and turbine engines, pressure often exhibits the characteristic of dynamic acoustic pressure superimposed on a large static pressure. Therefore, accurate real-time measurement of static pressure and high-frequency acoustic pressure is of great practical significance for improving the performance and life of gas turbines. High static pressure backgrounds often exceed the linear measurement range of the diaphragm of traditional EFPI fiber optic pressure sensors, making high static pressure measurements impossible. Furthermore, slowly varying signals such as static pressure often significantly affect the EFPI sensor's cavity length. This variation in EFPI sensor cavity length exhibits a superposition of a large-dynamic-range quasi-static direct current flow caused by static pressure and a small-dynamic-range high-frequency alternating current flow caused by acoustic pressure. Currently, acoustic pressure measurements in high static pressure backgrounds are difficult to achieve. Therefore, the development of novel sensor structures and corresponding precise dual-parameter demodulation algorithms to enable these complex environmental measurements is an urgent need.

[0003] In recent years, the fiber Fabry-Perot etalon (FPE) type sensing structure has become a research hotspot in the field of FPI pressure sensing. The structure of the FPE type sensor is as follows: Figure 2 As shown in Figure 1, it consists of two highly parallel, partially transmissive, high-reflection mirrors. The measurement principle is as follows: Figure 3As shown, the sensing function is mainly based on the change in the static pressure in the detection cavity and the change in the refractive index of the air between the reflectors caused by the acoustic disturbance. The advantages of this method are: (1) Pressure measurement can be achieved without involving the mechanical deformation of the diaphragm, with good frequency response, large dynamic range, and the sensor can still work normally under high sound pressure levels. (2) The high reflectivity FPE type sensor has high precision and a very sharp reflection spectrum, so it can achieve high-sensitivity detection of pressure parameters. The FPE type sensor is particularly suitable for high-sensitivity measurement of static pressure and sound pressure dual parameters in high static pressure environments.

[0004] Among existing demodulation technologies for fiber-optic FPI sensors, spectral demodulation based on white-light interferometry is the most commonly used. Spectral demodulation requires obtaining the spectral distribution of the interferometric light signal output by the fiber-optic FPI sensor. However, both scanning laser and grating spectrometer methods struggle to obtain spectral information in a very short time, resulting in high system costs and inability to meet the demodulation requirements of high-frequency sound pressure signals from fiber-optic extrinsic Fabry-Perot sensors. In the joint sensing and demodulation of dual parameters, a large dynamic range quasi-static parameter and a small dynamic range high-frequency component (e.g., Reference 1: Beijing Telemetry Technology Research Institute, Aerospace Changzheng Rocket Technology Co., Ltd., A Fiber-Optic Fiber-Emitting Physics (EFPI) Sensor Demodulation Device: CN201811393529.9 [P]. 2019-03-08; Reference 2: X. Fu et al., "Intensity Demodulation Based Fiber Sensor for Dynamic Measurement of Acoustic Wave and Lateral Pressure Simultaneously," in IEEE Photonics Journal, vol. 8, no. 6, pp. 1-13, December 2016), these methods typically employ a combination of broadband and narrowband light sources, or a broadband light source, a wavelength division multiplexer, and multiple detectors. This results in complex system structures and is prone to crosstalk between optical paths. Existing FPI sensor demodulation methods fail to meet the requirements for dual-parameter measurement of static and acoustic pressure in complex environments, limiting the further application of fiber-optic FPI sensors for measuring high-frequency acoustic signals in high static pressure environments.

[0005] As a fast and widely tunable laser, the Vernier tuned distributed Bragg reflector (VT-DBR) laser, based on the Vernier tuning effect, has been widely used in optical coherence tomography (OCT) and lidar research. Thanks to its flexible switching between fast full-spectrum scanning and precise single-wavelength narrow-linewidth output, it can simultaneously meet the light source requirements of multiple demodulation algorithms during FPE sensor measurements, making it an ideal light source for FPE multi-parameter sensing applications. Summary of the Invention

[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a sensing system and method for dual-parameter measurement of static pressure and sound pressure based on a Fabry-Perot etalon, so as to achieve high-speed demodulation of the sensor in an environment where low-frequency static pressure with a large dynamic range and high-frequency perturbation sound pressure coexist.

[0007] The technical solution of the present invention:

[0008] A sensing system for measuring static pressure and acoustic pressure dual parameters based on a Fabry-Perot etalon, comprising an optical fiber Fabry-Perot etalon-type pressure sensor 3, a wavelength control and synchronous acquisition module 4, a laser 5, a photodetector 6, a data processing module 7, and an optical fiber circulator 8;

[0009] The optical fiber Fabry-Perot etalon pressure sensor 3 is used to measure static pressure and sound pressure, and includes an inlet optical fiber 1 and an optical fiber Fabry-Perot etalon 2, which are connected to each other; an optical fiber circulator 8 is respectively connected to the optical fiber Fabry-Perot etalon pressure sensor 3, a laser 5, and a photodetector 6; a wavelength control and synchronous acquisition module 4 is respectively connected to the laser 5, the photodetector 6, and the data processing module 7; the wavelength control and synchronous acquisition module 4 controls the wavelength control and output of the laser 5; the wavelength control and synchronous acquisition module 4 simultaneously collects, converts, and transmits data from the photodetector 6 to the data processing module 7 according to clock synchronization;

[0010] The optical fiber circulator 8 introduces the optical signal from the laser 5 into the optical fiber Fabry-Perot etalon pressure sensor 3, and the reflected optical signal from the optical fiber Fabry-Perot etalon pressure sensor 3 passes through the optical fiber circulator 8 again and is detected by the photodetector 6; the photodetector 6 converts the detected optical signal into an analog signal, which is collected by the wavelength control and synchronous acquisition module 4 and then transmitted to the data processing module 7 for signal processing and feedback control; the wavelength control and synchronous acquisition module 4 selects the full spectrum scanning mode according to the received user instructions, and then selects the full spectrum scanning mode or the single wavelength output mode according to the threshold condition, thereby realizing dual-parameter detection of static pressure and dynamic sound pressure.

[0011] The laser 5 is a widely tunable wavelength scanning laser, specifically a distributed Bragg reflector based on the Vernier tuning effect. The optical fiber Fabry-Perot etalon 2 is a diaphragm-free structure.

[0012] A demodulation method for a sensing system for dual-parameter measurement of static pressure and acoustic pressure based on a Fabry-Perot etalon comprises the following steps:

[0013] 1) The wavelength control and synchronous acquisition module 4 controls the laser 5 to perform linear wavelength scanning, and synchronously collects intensity data through the photodetector 6 to obtain the full interference spectrum of the fiber Fabry-Perot etalon pressure sensor 3;

[0014] 2) Based on the full interference spectrum of the fiber Fabry-Perot etalon pressure sensor 3, the optical cavity length L under static pressure environment is calculated by white light interference signal processing algorithm. f , determine the static pressure, and at the same time determine the point where the slope of the Fabry-Perot cavity interference spectrum is maximum, that is, the wavelength λ0 corresponding to the orthogonal working point, so as to maximize the sensitivity of the optical fiber Fabry-Perot etalon pressure sensor 3;

[0015]

[0016] Where n is the refractive index in the cavity under a static pressure variation environment, L is the geometric cavity length of the fiber Fabry-Perot etalon 2;

[0017] The change in refractive index after a change in static pressure is Δn:

[0018]

[0019] The refractive index change of the Fabry-Perot cavity has a linear response to the change of the static pressure P, as shown in the following equation:

[0020] Δn=kΔP,

[0021] Wherein, k is a constant, and its value is 2.66×10 -9 , ΔP is the static pressure change;

[0022] The change in optical cavity length caused by the change in external static pressure is:

[0023] ΔL=LΔn=LkΔP;

[0024] 3) When the wavelength λ0 corresponding to the orthogonal working point is known, calculate the DC component of the interference spectrum signal intensity I DC, the laser 5 is controlled by the wavelength control and synchronous acquisition module 4 to lock the output wavelength λ0. At this time, the slope of the spectrum curve reaches its maximum value, the sensitivity of the optical fiber Fabry-Perot etalon pressure sensor 3 is the highest, and the wavelength λ0 operates within the quasi-linear range of the interference fringes, so that the return light signal intensity of the optical fiber Fabry-Perot etalon pressure sensor 3 and the optical path difference or the optical signal intensity and phase difference change in a linear relationship;

[0025] 4) For the fiber Fabry-Perot etalon pressure sensor 3, the phase change caused by the acoustic signal affects the intensity change of the optical signal, and the interference spectrum signal intensity I satisfies:

[0026]

[0027] Where r is the reflection coefficient of the reflector in the fiber Fabry-Perot etalon pressure sensor 3, q ​​is the phase angle corresponding to the wavelength, Δn2 is the change in the refractive index in the cavity caused by the high-frequency sound pressure perturbation, and n1 is the quasi-static refractive index parameter related to the static pressure parameter. is the initial phase;

[0028] 5) Real-time interference spectrum signal intensity I AC component I AC It is used to characterize the sound signal, analyze its spectrum, and obtain the sound pressure parameter information; according to the real-time interference spectrum signal intensity DC component I DC To reflect the drift of the orthogonal working point caused by the change of environmental static pressure; set the trigger threshold of the orthogonal calibration. When the DC component reaches the trigger condition, re-search the output wavelength that meets the orthogonal working point, thereby achieving self-adaptation and self-stabilization of the orthogonal working point.

[0029] The trigger thresholds of the orthogonal calibration are I up , I low ; When the DC component I DC Greater than I up or less than I low , triggering steps 1), 2), and 3) of locking the orthogonal working point, outputting a wavelength that satisfies the orthogonal working point; and on this basis, sequentially executing steps 4) and 5). I up The value is 1.2*I DC , I low The value is 0.8*I DC .

[0030] The white light interferometry signal processing algorithm includes Fourier transform [Z. Wang, Y. Jiang, W. Ding and R. Gao, "A White-Light Interferometry for the Measurement of High-Finesse FiberOptic EFPI Sensors," in IEEE Photonics Technology Letters, vol. 26, no. 21, pp. 2138-2141, 1 Nov. 1, 2014, doi: 10.1109 / LPT.2014.2332558.] and cross-correlation algorithm [Z. Jing and Q. Yu, "White light optical fiber EFPI sensor based on cross-correlation signal processing method," in Proceedings of 6th International Symposium on Test and Measurement (Academic, 2005), pp. 3509-3511.].

[0031] The sound pressure parameter information includes sound pressure frequency and sound pressure amplitude.

[0032] The wavelength control and synchronization acquisition module 4 can be composed of a computer, a single chip microcomputer or a field programmable gate array (FPGA) core board, etc., and has a built-in current lookup table for laser wavelength scanning control.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention is based on the Fabry-Perot etalon to achieve high-sensitivity measurement of static pressure and sound pressure, does not involve the mechanical deformation of the diaphragm, and has good frequency response and a large dynamic range.

[0035] 2. Thanks to the flexible tuning characteristics of the VT-DBR laser, the orthogonal working point intensity demodulation method realizes the demodulation of high-frequency perturbation sound signals. Combined with the spectral demodulation technology, the quasi-static cavity length is obtained, and the demodulation of static pressure and sound pressure is achieved completely in the same optical path. The system is compact and highly stable, with great cost advantages and has the value of promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the sensing system for dual-parameter measurement of static pressure and acoustic pressure based on the Fabry-Perot etalon.

[0037] Figure 2 This is the structural diagram of the FPE type sensor.

[0038] Figure 3 This is the sensing mechanism diagram of FPE type sensor.

[0039] Figure 4 The figure is a flow chart of a demodulation method for a sensing system based on a Fabry-Perot etalon for dual-parameter measurement of static pressure and acoustic pressure.

[0040] Figure 5 Schematic diagram of the interference spectrum of the fiber Fabry-Perot etalon.

[0041] In the figure: 1-introduction optical fiber; 2-optical fiber Fabry-Perot etalon; 3-optical fiber Fabry-Perot etalon type pressure sensor; 4-wavelength control and synchronous acquisition module; 5-laser; 6-photodetector; 7-data processing module; 8-optical fiber circulator. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is described in detail below in conjunction with the technical solutions and drawings, but this should not limit the scope of protection of the present invention.

[0043] A sensing system for static pressure and acoustic pressure dual-parameter measurement based on Fabry-Perot etalon (schematic diagram see Figure 1 ), including an optical fiber Fabry-Perot etalon pressure sensor 3, a wavelength control and synchronous acquisition module 4, a fast and widely tunable laser, a photodetector 6, a data processing module 7, and an optical fiber circulator 8, which can realize Fabry-Perot interferometric optical fiber static pressure measurement and dynamic acoustic pressure sensing in the same optical path.

[0044] A typical high-finesse fiber Fabry-Perot etalon pressure sensor 3 is composed of an inlet optical fiber 1 and a fiber Fabry-Perot etalon 2 connected to each other.

[0045] The wavelength control and synchronous acquisition module 4 is implemented using an FPGA, while the data processing module 7 is implemented on a computer. The FPGA control board achieves synchronous control and output of the current source, thereby controlling the output wavelength drive of the fast and widely tunable laser. The FPGA has a built-in current lookup table for controlling the laser wavelength. Data from the photodetector 6 is simultaneously collected, converted, and transmitted to the data processing module 7 through clock synchronization; the synchronization clock is set to 500kHz.

[0046] The wavelength control and synchronous acquisition module 4 selects full spectrum scanning mode or single wavelength output mode according to the command issued by the data processing module 7, and the wavelength switching frequency is 500kHz.

[0047] The fast and widely tunable laser uses a vernier-tuned distributed Bragg reflector (VT-DBR) laser. Its output wavelength is controlled by five injected currents: the left reflector current, the right reflector current, the phase block current, the gain current, and the semiconductor optical amplifier (SOA) current. By controlling the output wavelength using the left, right, and phase block currents, and adjusting the output optical power using the SOA injected current, wavelength switching can be achieved in nanoseconds.

[0048] The fast and widely tunable VT-DBR laser has a tuning band that can cover the C band, specifically 1527nm to 1567nm.

[0049] The optical fiber circulator 8 is used for transmitting optical signals. The optical signal from the fast and widely tunable VT-DBR laser passes through the optical fiber circulator 8 and is introduced into the optical fiber Fabry-Perot etalon pressure sensor 3. The reflected optical signal passes through the optical fiber circulator 8 again and is detected by the photodetector 6.

[0050] The photoelectric detector 6 is a 1550nm band high-speed photoelectric detector with an optical fiber input interface and DC coupling. It converts the detected light intensity signal into an analog signal, which is collected by the wavelength control and synchronization acquisition module 4 and then transmitted to the data processing module 7 for signal demodulation.

[0051] The performance of the fiber optic Fabry-Perot sensing system for static and dynamic sound pressure measurement was verified using a fiber optic Fabry-Perot etalon pressure sensor 3 with a geometric cavity length of 1500 μm. Figure 4 A schematic flow chart of the Fabry-Perot etalon demodulation method for measuring static and dynamic sound pressure using a fast and widely tunable VT-DBR laser is shown.

[0052] 1) In full spectrum scanning mode, obtain the interference spectrum of the optical fiber Fabry-Perot etalon pressure sensor 3, Figure 5 The figure shows the interference spectrum of the Fabry-Perot etalon. The optical path L of the sensor under static pressure can be calculated based on the interference spectrum. f The wavelength with the maximum full-spectrum slope in the free spectrum region (FSR) is determined. This wavelength, corresponding to the highest sensitivity of sound pressure measurement, is used as the operating wavelength λ0 for the orthogonal operating point intensity demodulation method. The laser output wavelength is controlled at λ0 by controlling the laser's drive current or operating temperature. The phase change caused by sound pressure is linearly proportional to the intensity of the reflected light. Utilizing this phenomenon, optical intensity demodulation of sound pressure changes can be achieved.

[0053] 2) Calculate the optical path L under static pressure environment based on the interference spectrum of the fiber Fabry-Perot etalon pressure sensor 3 f For the optical fiber Fabry-Perot etalon type pressure sensor 3,

[0054]

[0055] Where n is the refractive index in the cavity under static pressure, and L is the geometric cavity length of the fiber Fabry-Perot etalon. The change in refractive index Δn after the static pressure changes can be obtained:

[0056]

[0057] The refractive index change of the FP cavity has a linear response to the change of the static pressure P, as shown in the following equation:

[0058] Δn=kΔP,

[0059] Δn is the change in refractive index after the static pressure changes, λ is the wavelength, k is a constant, and at room temperature k≈2.66×10 -9 .

[0060] From the above formula, we can see that the cavity length change ΔL caused by the external static pressure change is expressed as

[0061] ΔL=LΔn=kLΔP

[0062] 3) When the wavelength λ0 corresponding to the orthogonal working point is known, calculate the DC component of the interference spectrum signal intensity I DC , through the wavelength control and synchronous acquisition module 4, the fast and wide tunable laser is controlled to lock the output wavelength to λ0, and the wavelength λ0 operates within the quasi-linear range of the interference fringes, so that the intensity of the optical signal returned by the sensor is basically linear with the change of the optical path difference or phase difference;

[0063] 4) For the fiber Fabry-Perot etalon pressure sensor 3, the phase change caused by the acoustic signal affects the light intensity change, and the interference spectrum signal intensity I satisfies:

[0064]

[0065] Where r is the reflection coefficient of the reflector in the fiber Fabry-Perot etalon pressure sensor 3, q ​​is the phase angle corresponding to the wavelength, L is the geometric cavity length of the fiber Fabry-Perot etalon, Δn2 is the change in the refractive index in the cavity caused by the high-frequency sound pressure perturbation, and n1 is the quasi-static refractive index parameter related to the static pressure parameter. is the initial phase.

[0066] 5) Real-time interference spectrum signal intensity AC component I AC Characterize the acoustic signal, perform Fourier transform spectrum analysis on it, obtain parameter information such as sound pressure frequency amplitude, and calculate the DC component I of the real-time interference spectrum signal intensity. DC To reflect the drift of the orthogonal working point caused by the change of environmental static pressure;

[0067] I DC >I up orI DC <I low ,

[0068] Among them I up , I low are the trigger thresholds for quadrature lock. When the DC component I DC Greater than a certain value I up When or less than a certain value I low , trigger the steps 1), 2), and 3) of locking the orthogonal working point, and output the wavelength that meets the orthogonal working point. And on this basis, perform steps 4) and 5) in sequence, where I up and I low The values ​​are 1.2*I DC and 0.8*I DC , thereby realizing the adaptive and self-stabilizing mechanism of the orthogonal working point.

Claims

1. A sensing system for measuring static pressure and acoustic pressure dual parameters based on a Fabry-Perot etalon, characterized in that: The sensing system for measuring the dual parameters of static pressure and acoustic pressure based on a Fabry-Perot etalon comprises an optical fiber Fabry-Perot etalon-type pressure sensor (3), a wavelength control and synchronous acquisition module (4), a laser (5), a photodetector (6), a data processing module (7) and an optical fiber circulator (8); The optical fiber Fabry-Perot etalon type pressure sensor (3) is used to measure static pressure and sound pressure, and comprises an inlet optical fiber (1) and an optical fiber Fabry-Perot etalon (2), which are connected; an optical fiber circulator (8) is respectively connected to the optical fiber Fabry-Perot etalon type pressure sensor (3), a laser (5), and a photodetector (6); a wavelength control and synchronous acquisition module (4) is respectively connected to the laser (5), the photodetector (6), and a data processing module (7); the wavelength control and synchronous acquisition module (4) controls the wavelength control and output of the laser (5); the wavelength control and synchronous acquisition module (4) simultaneously acquires and converts data of the photodetector (6) according to clock synchronization and transmits the data to the data processing module (7); The optical fiber circulator (8) introduces the optical signal from the laser (5) into the optical fiber Fabry-Perot etalon pressure sensor (3); the reflected optical signal from the optical fiber Fabry-Perot etalon pressure sensor (3) passes through the optical fiber circulator (8) again and is detected by the photodetector (6); the photodetector (6) converts the detected optical signal into an analog signal, which is collected by the wavelength control and synchronous acquisition module (4) and then transmitted to the data processing module (7) for signal processing and feedback control; the wavelength control and synchronous acquisition module (4) selects a full spectrum scanning mode according to a received user instruction, and then selects a full spectrum scanning mode or a single wavelength output mode according to a threshold condition, thereby realizing dual parameter detection of static pressure and dynamic sound pressure.

2. The sensing system for measuring static pressure and sound pressure dual parameters based on a Fabry-Perot etalon according to claim 1, characterized in that: The laser (5) is a widely tunable wavelength scanning laser.

3. The sensing system for measuring static pressure and sound pressure dual parameters based on a Fabry-Perot etalon according to claim 2, characterized in that: The widely tunable wavelength scanning laser is a distributed Bragg reflector based on the Vernier tuning effect.

4. The sensing system for measuring static pressure and sound pressure dual parameters based on a Fabry-Perot etalon according to claim 1 or 2, characterized in that: The optical fiber Fabry-Perot etalon (2) is a membrane-free structure.

5. A demodulation method for a sensing system for dual-parameter measurement of static pressure and acoustic pressure based on a Fabry-Perot etalon, characterized in that: The following steps are involved: 1) A wavelength control and synchronous acquisition module (4) controls a laser (5) to perform linear wavelength scanning, synchronously acquires intensity data through a photodetector (6), and obtains a full interference spectrum of the optical fiber Fabry-Perot etalon pressure sensor (3); 2) Based on the full interference spectrum of the fiber Fabry-Perot etalon pressure sensor (3), the optical cavity length L under static pressure is calculated by white light interference signal processing algorithm. f , determine the static pressure, and at the same time determine the point where the slope of the Fabry-Perot cavity interference spectrum is the largest, that is, the wavelength λ0 corresponding to the orthogonal working point, so that the sensitivity of the optical fiber Fabry-Perot etalon type pressure sensor (3) is maximized; Where n is the refractive index in the cavity under static pressure variation, L is the geometric cavity length of the fiber Fabry-Perot etalon (2); The change in refractive index after a change in static pressure is Δn: The refractive index change of the Fabry-Perot cavity has a linear response to the change of static pressure P, as shown below: Δn=kΔP, Where k is a constant and ΔP is the change in static pressure; The change in optical cavity length caused by the change in external static pressure is: ΔL=LΔn=LkΔP; 3) When the wavelength λ0 corresponding to the orthogonal working point is known, calculate the DC component I of the interference spectrum signal intensity DC , the laser (5) is controlled by the wavelength control and synchronization acquisition module (4) to lock the output wavelength λ0, at which time the slope of the spectrum curve reaches a maximum value, the sensitivity of the optical fiber Fabry-Perot etalon type pressure sensor (3) is the highest, and the wavelength λ0 works within the quasi-linear range of the interference fringes, so that the return light signal intensity of the optical fiber Fabry-Perot etalon type pressure sensor (3) changes in a linear relationship with the optical path difference or the light signal intensity and the phase difference; 4) For the optical fiber Fabry-Perot etalon type pressure sensor (3), the phase change caused by the acoustic signal affects the intensity change of the optical signal, and the interference spectrum signal intensity I satisfies: Wherein, r is the reflection coefficient of the reflector in the fiber Fabry-Perot etalon pressure sensor (3), q is the phase angle corresponding to the wavelength, Δn2 is the change of the refractive index in the cavity caused by the high-frequency sound pressure perturbation, n1 is the quasi-static refractive index parameter related to the static pressure parameter, is the initial phase; 5) Real-time interference spectrum signal intensity I AC component I AC It is used to characterize the sound signal, analyze its spectrum, and obtain the sound pressure parameter information; according to the real-time interference spectrum signal intensity DC component I DC To reflect the drift of the orthogonal working point caused by the change of environmental static pressure; set the trigger threshold of the orthogonal calibration. When the DC component reaches the trigger condition, re-search the output wavelength that meets the orthogonal working point, so as to achieve the self-adaptation and self-stabilization of the orthogonal working point.

6. The demodulation method of the sensing system for measuring static pressure and sound pressure dual parameters based on the Fabry-Perot etalon according to claim 5, characterized in that: The trigger thresholds of the orthogonal calibration are respectively up ,I low ; When the DC component I DC Greater than I up or less than I low , triggering steps 1), 2), and 3) of locking the orthogonal working point, and outputting a wavelength that satisfies the orthogonal working point; on this basis, executing steps 4) and 5) in sequence.

7. The demodulation method of the sensing system for measuring static pressure and sound pressure dual parameters based on the Fabry-Perot etalon according to claim 5 or 6, characterized in that: I up The value is 1.2*I DC , I low The value is 0.8*I DC .

8. The demodulation method of the sensing system for measuring static pressure and sound pressure dual parameters based on the Fabry-Perot etalon according to claim 5, characterized in that: The white light interference signal processing algorithm includes Fourier transform and cross-correlation algorithm.

9. The demodulation method of the sensing system for measuring static pressure and sound pressure dual parameters based on the Fabry-Perot etalon according to claim 5, characterized in that: The value of k in step 2) is 2.66×10 -9 .

10. The demodulation method of the sensing system for measuring static pressure and sound pressure dual parameters based on the Fabry-Perot etalon according to claim 5, characterized in that: The sound pressure parameter information includes sound pressure frequency and sound pressure amplitude.

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