CN115265615A - Sensing system and method for measuring static pressure and sound pressure double parameters based on Fabry-Perot etalon - Google Patents
Sensing system and method for measuring static pressure and sound pressure double parameters based on Fabry-Perot etalon Download PDFInfo
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Abstract
The invention belongs to the technical field of optical fiber sensing, and provides a sensing system and a sensing method for measuring static pressure and sound pressure double parameters based on a Fabry-Perot etalon, so as to realize high-speed demodulation of a sensor in an environment where large dynamic range low-frequency static pressure and high-frequency perturbation sound pressure exist at the same time. The system comprises 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 invention adopts the wide tunable laser, simplifies the system complexity of low-frequency static pressure and high-frequency perturbation sound pressure measurement, reduces the overall cost, and has better frequency response and larger dynamic range according to the optical fiber Fabry-Perot standard which does not relate to the mechanical deformation of the diaphragm; and measuring low-frequency static pressure and high-frequency perturbation sound pressure by using a white light interference signal processing algorithm and a fixed working point algorithm. The invention can be suitable for typical applications that aeroacoustics, turbine engines and the like need to rapidly detect dynamic sound pressure and static pressure.
Description
Technical Field
The invention relates to the technical field of optical fiber sensing, in particular to a sensing system and a sensing method for measuring static pressure and sound pressure double parameters based on a Fabry-Perot etalon.
Background
The Fabry-Perot interference (FPI) type optical fiber sensor can be designed into various structures sensitive to sound pressure, is a typical representative product of an optical fiber sensing technology due to the advantages of compact structure, high sensitivity, electromagnetic interference resistance and the like, is widely applied to monitoring parameters such as pressure, sound and the like, and plays an important role in the fields of industrial manufacturing, medical detection, aerospace and the like. Along with the expansion of the application field of the FPI sensor, the measurement of high-frequency sound pressure signals under the background of high static pressure gradually becomes the bottleneck of the application of the sensor. Currently, a diaphragm type extrinsic fabry-perot interference (EFPI) optical fiber pressure sensor is common, and the pressure sensor senses a pressure parameter by detecting a fabry-perot cavity length change caused by the pressure deformation of a diaphragm. Since the sensor mainly depends on the mechanical deformation of the diaphragm to realize the measurement performance of the sensor, the performance indexes of the sensor, such as sensitivity, resolution, dynamic range and the like, are often limited by parameters of the diaphragm, such as material, thickness, radius and the like. On the other hand, in typical applications such as aeroacoustics and turbine engines, pressure often shows the characteristic that dynamic sound pressure is superposed on large static pressure, and real-time accurate measurement of static pressure and high-frequency sound pressure has important practical significance for improving the performance and the service life of a gas turbine. The high static pressure background often exceeds the linear measurement range of the diaphragm of the traditional EFPI optical fiber pressure sensor, so that the measurement of the high static pressure cannot be realized. Meanwhile, slow-varying signals such as static pressure often have a significant influence on the cavity length of the EFPI sensor, the cavity length change of the EFPI sensor presents the characteristic of superposition of large dynamic range quasi-static direct current caused by static pressure and small dynamic range high-frequency alternating current caused by sound pressure, and at present, sound pressure measurement under the background of high static pressure is difficult to realize. Therefore, a novel sensor structure and a corresponding dual-parameter accurate demodulation algorithm for realizing the complex environment measurement are problems to be solved urgently.
In recent years, a fiber fabry-perot etalon (FPE) type sensing structure has become a hot research point in the FPI pressure sensing direction. The structure of the FPE type sensor is shown in fig. 2 and consists of two highly parallel, partially transmissive high reflection mirrors. The measurement principle is shown in fig. 3, and the sensing function is realized mainly by relying on the change of the static pressure in the detection cavity and the change of the air refractive index between the reflectors caused by the sound wave disturbance. The method has the advantages that: (1) The pressure measurement can be realized without involving the mechanical deformation part of the diaphragm, the frequency response is good, the dynamic range is large, and the sensor can still normally work under high sound pressure level. (2) The FPE type sensor with high reflectivity has high fineness and very sharp reflection spectral line, so that high-sensitivity detection of pressure parameters can be realized. The FPE type sensor is particularly suitable for high-sensitivity measurement of double parameters of static pressure and sound pressure in a high-static-pressure environment.
Among the existing demodulation techniques of fiber FPI sensing, a spectral demodulation method based on white light interference is the most commonly used method. Spectrum demodulation needs to acquire the spectrum distribution of an interference light signal output by the optical fiber FPI sensor, no matter a scanning laser method, a grating spectrometer method and the like are adopted, spectrum information is difficult to acquire in a very short time, the system cost is high, and the requirement of high-frequency sound pressure signal demodulation of the optical fiber extrinsic Fabry-Perot sensor cannot be met. In the large dynamic range quasi-static parameter and small dynamic range high-frequency component double-parameter combined sensing demodulation technology [ as document 1: beijing telemetry technical research institute, aerospace Long-March rocket technology Limited company, an optical fiber EFPI sensor demodulation device is CN201811393529.9[ P ].2019-03-08; document 2: X.Fu et al, "Intensity modulation Based Fiber Sensor for Dynamic Measurement of ecological Wave and terrestrial Pressure filtration," in IEEE Photonics Journal, vol.8, no.6, pp.1-13, dec.2016; generally, a method of combining a broadband light source and a narrow-band light source or combining a broadband light source, a wavelength division multiplexer and a plurality of detectors is adopted, the system structure is complex, and crosstalk easily occurs between light paths. The existing demodulation method of the FPI sensor is difficult to meet the application requirements of complex environment on static pressure and sound pressure double-parameter measurement, and further application of the optical fiber FPI sensor in the high-frequency sound signal measurement direction under the high static pressure background is limited.
A distributed Bragg reflector (VT-DBR) laser based on Vernier tuning effect is used as a fast wide tunable laser, is widely applied to the research field of Optical Coherence Tomography (OCT) and laser radar, benefits from the flexible switching characteristic between two modes of fast full-spectrum scanning and accurate single-wavelength narrow-linewidth output, can simultaneously meet the light source requirements of various demodulation algorithms in the measurement process of an FPE (Fabry-Perot interferometer) sensor, and is an ideal light source in FPE multi-parameter sensing measurement application.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a sensing system and a sensing method for measuring double parameters of static pressure and sound pressure based on a Fabry-Perot etalon, and realizes high-speed demodulation of a sensor in an environment where large dynamic range low-frequency static pressure and high-frequency perturbation sound pressure exist at the same time.
The technical scheme of the invention is as follows:
a sensing system for measuring static pressure and sound pressure double parameters 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 photoelectric detector 6, a data processing module 7 and an optical fiber circulator 8;
the optical fiber Fabry-Perot etalon type pressure sensor 3 is used for measuring static pressure and sound pressure, and comprises a lead-in optical fiber 1 and an optical fiber Fabry-Perot etalon 2 which are connected; the optical fiber circulator 8 is respectively connected with the optical fiber Fabry-Perot etalon type pressure sensor 3, the laser 5 and the photoelectric detector 6; the wavelength control and synchronous acquisition module 4 is respectively connected with the laser 5, the photoelectric detector 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 is synchronous according to the clock, and simultaneously acquires and converts data of the photoelectric detector 6 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 type pressure sensor 3, and the reflected optical signal from the optical fiber Fabry-Perot etalon type pressure sensor 3 is detected by the photoelectric detector 6 through the optical fiber circulator 8 again; the photoelectric detector 6 converts the detected optical signals into analog signals, and the analog signals are transmitted to the data processing module 7 for signal processing and feedback control after being collected by the wavelength control and synchronous collection module 4; the wavelength control and synchronous acquisition module 4 selects a full spectrum scanning mode according to the received user instruction, and then selects the full spectrum scanning mode or a single-wavelength output mode according to a threshold condition, thereby realizing double-parameter detection of static pressure and dynamic sound pressure.
The laser 5 is a wide tunable wavelength scanning laser, in particular a distributed bragg reflector based on Vernier tuning effect. The optical fiber Fabry-Perot etalon 2 is of a non-membrane structure.
A demodulation method of a sensing system based on static pressure and sound pressure double-parameter measurement of a Fabry-Perot etalon comprises the following steps:
1) The wavelength control and synchronous acquisition module 4 controls the laser 5 to perform linear wavelength scanning, and intensity data are synchronously acquired through the photoelectric detector 6 to obtain the full interference spectrum of the optical fiber Fabry-Perot etalon type pressure sensor 3;
2) Calculating the optical cavity length L under the static pressure environment according to the full interference spectrum of the optical fiber Fabry-Perot etalon type pressure sensor 3 and a white light interference signal processing algorithm f Determining the size of static pressure, and simultaneously determining the position with the maximum slope of the interference spectrum of the Fabry-Perot cavity, namely the wavelength lambda corresponding to the orthogonal working point 0 The sensitivity of the optical fiber fabry-perot etalon type pressure sensor 3 is maximized;
wherein n is the intracavity refractive index under the static pressure change environment, and L is the geometric cavity length of the optical fiber Fabry-Perot etalon 2;
the amount of change in refractive index after the static pressure is changed is Δ n:
the change of the refractive index of the Fabry-Perot cavity has a linear response to the change of the static pressure P, and the following formula is shown:
Δn＝kΔP，
wherein k is constant and is 2.66 multiplied by 10 under normal temperature environment -9 Delta P is the static pressure variation;
the optical cavity length change due to the external static pressure change is:
ΔL＝LΔn＝LkΔP；
3) Wavelength λ at a known quadrature operating point 0 In the case of (1), the direct current component I of the interference spectrum signal intensity is calculated DC The laser 5 is controlled by the wavelength control and synchronous acquisition module 4 to lock the output wavelength lambda 0 At this time, the slope of the spectral curve has a maximum value, the sensitivity of the fiber Fabry-Perot etalon type pressure sensor 3 is the highest, and the wavelength λ is the same as that of the optical fiber Fabry-Perot etalon type pressure sensor 3 0 Working in the quasi-linear range of the interference fringe, so that the intensity of the optical signal returned by the optical fiber Fabry-Perot etalon type pressure sensor 3 is in a linear relation with the optical path difference or the intensity of the optical signal is changed with 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 intensity I of the interference spectrum signal satisfies the following conditions:
wherein r is a reflection coefficient of a reflector in the optical fiber Fabry-Perot etalon type pressure sensor 3, q is a phase angle corresponding to a wavelength, and Δ n 2 Is high frequency sound pressure microIntra-cavity refractive index change due to perturbation, n 1 A quasi-static refractive index parameter that is a function of a static pressure parameter,
is the initial phase;
5) Real-time interference spectrum signal intensity I AC component I AC The method is used for representing the acoustic signal and analyzing the frequency spectrum of the acoustic signal to obtain sound pressure parameter information; direct current component I according to real-time interference spectrum signal intensity DC To reflect the drift condition of the orthogonal working point caused by the change of the environmental static pressure; and setting a trigger threshold value of the orthogonal calibration, and searching and outputting the wavelength meeting the orthogonal working point again when the direct current component reaches a trigger condition, thereby realizing the self-adaption and self-stabilization of the orthogonal working point.
The trigger threshold values of the orthogonal calibration are respectively I up 、I low (ii) a When the direct current component I DC Is greater than I up Or less than I low Triggering the steps 1), 2) and 3) of locking the orthogonal working point, and outputting the wavelength meeting the orthogonal working point; and 4) sequentially executing steps 4) and 5) on the basis. I is up The value is 1.2 × I DC ，I low The value is 0.8 × I DC 。
The White Light interference signal processing algorithms include Fourier transform [ Z.Wang, Y.Jiang, W.Ding and R.Gao, "A White-Light interference for the Measurement of High-finement Fiber optics EFPI Sensors," in IEEE Photonics technologies Letters, vol.26, no.21, pp.2138-2141,1Nov.1,2014, doi.
The sound pressure parameter information includes a sound pressure frequency and a sound pressure amplitude.
The wavelength control and synchronous acquisition module 4 can be composed of a computer, a singlechip or a Field Programmable Gate Array (FPGA) core board and the like, and a current lookup table for controlling laser wavelength scanning is arranged in the wavelength control and synchronous acquisition module.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention realizes high-sensitivity measurement of static pressure and sound pressure based on the Fabry-Perot etalon without involving the mechanical deformation part of the diaphragm, and has good frequency response and larger dynamic range.
2. The characteristic of flexible tuning of the VT-DBR laser is benefited, the demodulation of high-frequency perturbation sound signals is realized in an orthogonal working point intensity demodulation mode, the quasi-static cavity length is obtained by matching with a spectrum demodulation technology, the demodulation of static pressure and sound pressure is completely realized in the same optical path, the system is compact and high in stability, the cost advantage is very high, and the popularization and application value is realized.
Drawings
Fig. 1 is a schematic diagram of a sensing system for measuring static pressure and sound pressure based on a fabry-perot etalon.
Fig. 2 is a structural view of an FPE type sensor.
FIG. 3 is a diagram of the sensing mechanism of the FPE type sensor.
Fig. 4 is a schematic flow chart of a sensing system demodulation method based on static pressure and sound pressure dual-parameter measurement of a fabry-perot etalon.
FIG. 5 is a schematic diagram of an interference spectrum of a fiber Fabry-Perot etalon.
In the figure: 1-leading in optical fiber; 2-fiber Fabry-Perot etalon; 3-fiber Fabry-Perot etalon type pressure sensor; 4-wavelength control and synchronous acquisition module; 5-a laser; 6-a photodetector; 7-a data processing module; 8-fiber circulator.
Detailed Description
The following detailed description of the present invention is provided in conjunction with the accompanying drawings and the accompanying claims, which should not be taken to limit the scope of the present invention.
A sensing system (a structural schematic diagram is shown in figure 1) for measuring static pressure and sound 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 fast wide tunable laser, a photoelectric detector 6, a data processing module 7 and an optical fiber circulator 8, and Fabry-Perot interference type optical fiber static pressure measurement and dynamic sound pressure sensing can be achieved in the same optical path.
A typical high-fineness optical fiber Fabry-Perot etalon type pressure sensor 3 is formed by connecting a lead-in optical fiber 1 and an optical fiber Fabry-Perot etalon 2.
The wavelength control and synchronous acquisition module 4 is realized by adopting an FPGA, and the data processing module 7 is realized on a computer. The FPGA control panel realizes current source current synchronous control and output, thereby controlling the output wavelength drive of the fast wide tunable laser. A current lookup table for controlling laser wavelength is arranged in the FPGA, and data of the photoelectric detector 6 is acquired, converted and transmitted to the data processing module 7 through clock synchronization; the synchronous clock is set to 500kHz.
The wavelength control and synchronous acquisition module 4 selects a full spectrum scanning mode or a single wavelength output mode according to a command sent by the data processing module 7, and the wavelength switching frequency is 500kHz.
The fast wide tunable laser is a vernier tuning distributed Bragg reflector (VT-DBR) laser, the output wavelength is controlled by 5 paths of injection current, namely left reflector current, right reflector current, phase region current, gain current and Semiconductor Optical Amplifier (SOA) current. The output wavelength is controlled by the current of the left reflector, the current of the right reflector and the current of the phase area, and the output optical power is adjusted by the current injected by the SOA, so that the wavelength switching of nanosecond level can be realized.
The tuning waveband of the fast wide tunable VT-DBR laser can cover a C waveband, and specifically ranges from 1527nm to 1567nm.
The optical fiber circulator 8 is used for transmitting optical signals, the optical signals from the fast and wide tunable VT-DBR laser are led into the optical fiber Fabry-Perot etalon type pressure sensor 3 after passing through the optical fiber circulator 8, and reflected optical signals are detected by the photoelectric detector 6 after passing through the optical fiber circulator 8 again.
The photoelectric detector 6 is a 1550nm waveband high-speed photoelectric detector with an optical fiber input interface and direct current coupling, converts detected light intensity signals into analog signals, and transmits the analog signals to the data processing module 7 for signal demodulation after the analog signals are collected by the wavelength control and synchronous collection module 4.
The performance verification of the optical fiber Fabry-Perot sensing system for measuring static pressure and dynamic sound pressure is performed by adopting the optical fiber Fabry-Perot etalon type pressure sensor 3 with the geometric cavity length of 1500 mu m, and fig. 4 shows a schematic flow chart of a Fabry-Perot etalon demodulation method based on the static pressure and dynamic sound pressure measurement of a fast and wide tunable VT-DBR laser.
1) In the full spectrum scanning mode, the interference spectrum of the optical fiber Fabry-Perot etalon type pressure sensor 3 is obtained, FIG. 5 shows the interference spectrum of the Fabry-Perot etalon, and the optical path L of the sensor in the static pressure environment can be calculated according to the interference spectrum f Determining the wavelength point with the maximum full spectrum slope in the Free Spectral Region (FSR), i.e. the wavelength corresponding to the maximum sound pressure measurement sensitivity, and using the wavelength as the working wavelength lambda of the orthogonal working point intensity demodulation method 0 Controlling the laser output wavelength at lambda by controlling the laser drive current or operating temperature 0 . The phase change caused by the sound pressure and the light intensity of the reflected light form a linear function relationship, and the light intensity demodulation of the sound pressure variation can be realized by utilizing the phenomenon.
2) Calculating the optical path L under the static pressure environment according to the interference spectrum of the optical fiber Fabry-Perot etalon type pressure sensor 3 f . For a fiber fabry-perot etalon type pressure sensor 3,
wherein n is the intracavity refractive index under the static pressure environment, L is the geometric cavity length of the optical fiber Fabry-Perot etalon, and the variable quantity delta n of the refractive index after the static pressure is changed can be obtained:
the refractive index change of the FP cavity has a linear response to the change in static pressure P as shown in the following equation:
Δn＝kΔP，
delta n is the variation of the refractive index after the static pressure is changed, lambda is the wavelength, k is a constant, and k is approximately equal to 2.66 multiplied by 10 under the normal temperature environment -9 。
From the above equation, the cavity length change Δ L due to the variation of the external static pressure is expressed as
ΔL＝LΔn＝kLΔP
3) Wavelength λ at a known quadrature operating point 0 In the case of (1), the direct current component I of the interference spectrum signal intensity is calculated DC The wavelength control and synchronous acquisition module 4 controls the fast wide tunable laser to lock the output wavelength to be lambda 0 Wavelength λ 0 Working in the quasi-linear range of the interference fringe, so that the intensity of the return light signal of the sensor is basically in linear relation with the optical path difference or the phase difference change;
4) For the optical fiber Fabry-Perot etalon type pressure sensor 3, the phase change caused by the acoustic signal affects the light intensity change, and the interference spectrum signal intensity I satisfies the following conditions:
wherein r is the reflection coefficient of the reflector in the optical fiber Fabry-Perot etalon type pressure sensor 3, q is the phase angle corresponding to the wavelength, L is the geometric cavity length of the optical fiber Fabry-Perot etalon, and delta n 2 For refractive index variations in the cavity caused by high-frequency sound pressure perturbations, n 1 Is a quasi-static refractive index parameter related to a static pressure parameter,
is the initial phase.
5) Real-time interference spectrum signal intensity alternating current component I AC Characterizing the acoustic signal, carrying out Fourier transform spectrum analysis on the acoustic signal to obtain parameter information such as sound pressure frequency amplitude and the like, and according to the direct current component I of the real-time interference spectrum signal intensity DC To reflect the condition that the orthogonal working point drifts due to the change of the environmental static pressure;
I DC ＞I up orI DC ＜I low ，
in which I up 、I low Are all trigger thresholds of quadrature locking when the DC component I DC Greater than a certain value I up At or below a certain value I low And triggering the steps 1), 2) and 3) of locking the orthogonal working point, and outputting the wavelength meeting the orthogonal working point. And on the basis of the above-mentioned operation steps 4) and 5) are successively implemented, in which I) up And I low Are each 1.2 × I DC And 0.8 × I DC Therefore, the self-adaption and self-stabilization mechanism of the orthogonal working point is realized.
Claims (10)
1. A sensing system based on static pressure and sound pressure double-parameter measurement of a Fabry-Perot etalon is characterized by comprising an optical fiber Fabry-Perot etalon type pressure sensor (3), a wavelength control and synchronous acquisition module (4), a laser (5), a photoelectric detector (6), a data processing module (7) and an optical fiber circulator (8);
the optical fiber Fabry-Perot etalon type pressure sensor (3) is used for measuring static pressure and sound pressure and comprises a lead-in optical fiber (1) and an optical fiber Fabry-Perot etalon (2) which are connected; the optical fiber circulator (8) is respectively connected with the optical fiber Fabry-Perot etalon type pressure sensor (3), the laser (5) and the photoelectric detector (6); the wavelength control and synchronous acquisition module (4) is respectively connected with the laser (5), the photoelectric detector (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) is synchronous according to a clock, and simultaneously acquires and converts data of the photoelectric detector (6) 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 type pressure sensor (3), and the reflected optical signal from the optical fiber Fabry-Perot etalon type pressure sensor (3) is detected by the photoelectric detector (6) through the optical fiber circulator (8); the photoelectric detector (6) converts the detected optical signals into analog signals, and the analog signals are transmitted to the data processing module (7) for signal processing and feedback control after being acquired by the wavelength control and synchronous acquisition module (4); the wavelength control and synchronous acquisition module (4) selects a full spectrum scanning mode according to the received user instruction, and then selects the full spectrum scanning mode or a single-wavelength output mode according to a threshold condition, so that double-parameter detection of static pressure and dynamic sound pressure is realized.
2. The fabry-perot etalon-based sensing system for dual parameter measurement of static and acoustic pressure according to claim 1, wherein the laser (5) is a widely tunable wavelength scanning laser.
3. The fabry-perot etalon-based sensing system for dual parameter measurement of static and acoustic pressure according to claim 2, wherein the widely tunable wavelength-swept laser is a distributed bragg reflector based on Vernier tuning effect.
4. The sensing system based on dual parameter measurement of static pressure and acoustic pressure of a fabry-perot etalon of claim 1 or 2, wherein the fiber fabry-perot etalon (2) is a membrane-free structure.
5. A demodulation method of a sensing system based on static pressure and sound pressure double-parameter measurement of a Fabry-Perot etalon is characterized by comprising the following steps:
1) The wavelength control and synchronous acquisition module (4) controls a laser (5) to perform linear wavelength scanning, and intensity data are synchronously acquired through a photoelectric detector (6) to obtain a full interference spectrum of the optical fiber Fabry-Perot etalon type pressure sensor (3);
2) According to the full interference spectrum of the optical fiber Fabry-Perot etalon type pressure sensor (3), and through a white light interference signal processing algorithm, the optical cavity length L in a static pressure environment is calculated f Determining the static pressure, and determining the maximum slope of interference spectrum of Fabry-Perot cavity, i.e. the wavelength lambda corresponding to the orthogonal working point 0 To maximize the sensitivity of a fiber Fabry-Perot etalon type pressure sensor (3)Large;
wherein n is the intracavity refractive index in the static pressure change environment, and L is the geometric cavity length of the optical fiber Fabry-Perot etalon (2);
the amount of change in refractive index after the static pressure is changed is Δ n:
the change of the refractive index of the Fabry-Perot cavity has a linear response to the change of the static pressure P, and the following formula is shown:
Δn＝kΔP，
wherein k is a constant and Δ P is a static pressure variation;
the optical cavity length change due to the external static pressure change is:
ΔL＝LΔn＝LkΔP；
3) Wavelength λ at a known quadrature operating point 0 In the case of (1), the direct current component I of the interference spectrum signal intensity is calculated DC The laser (5) is controlled by the wavelength control and synchronous acquisition module (4) to lock the output wavelength lambda 0 When the slope of the spectral curve has a maximum value, the sensitivity of the fiber Fabry-Perot etalon type pressure sensor (3) is the highest, and the wavelength lambda is set to be the same as that of the optical fiber Fabry-Perot etalon type pressure sensor 0 Working in a quasi-linear range of interference fringes, so that the intensity of a return light signal of the optical fiber Fabry-Perot etalon type pressure sensor (3) is in a linear relation with an optical path difference or the intensity of the light signal is changed with a phase difference;
4) For the optical fiber Fabry-Perot etalon type pressure sensor (3), the phase change caused by the acoustic signal influences the intensity change of the optical signal, and the intensity I of the interference spectrum signal satisfies the following conditions:
wherein r is a reflection coefficient of a reflector in the optical fiber Fabry-Perot etalon type pressure sensor (3), q is a phase angle corresponding to a wavelength, and delta n 2 For refractive index variations in the cavity caused by high-frequency sound pressure perturbations, n 1 Is a quasi-static refractive index parameter related to a static pressure parameter,
is the initial phase;
5) Real-time interference spectrum signal intensity I AC component I AC The method is used for representing the acoustic signal and analyzing the frequency spectrum of the acoustic signal to obtain sound pressure parameter information; direct current component I according to real-time interference spectrum signal intensity DC To reflect the drift condition of the orthogonal working point caused by the change of the environmental static pressure; and setting a trigger threshold value of the orthogonal calibration, and searching and outputting the wavelength meeting the orthogonal working point again when the direct current component reaches a trigger condition, thereby realizing the self-adaption and self-stabilization of the orthogonal working point.
6. The demodulation method for sensing system based on dual parameter measurement of static pressure and sound pressure of Fabry-Perot etalon according to claim 5, wherein the trigger threshold of the orthogonal calibration is I up 、I low (ii) a When the direct current component I DC Is greater than I up Or less than I low Triggering the steps 1), 2) and 3) of locking the orthogonal working point, and outputting the wavelength meeting the orthogonal working point; and 4) sequentially executing steps 4) and 5) on the basis.
7. The demodulation method of the sensing system based on the static pressure and sound pressure dual-parameter measurement of the Fabry-Perot etalon according to claim 5 or 6, wherein the I is up The value is 1.2 × I DC ，I low The value is 0.8 × I DC 。
8. The method for demodulating the sensing system based on dual parameter measurement of static pressure and acoustic pressure of Fabry-Perot etalon of claim 5, wherein the white light interference signal processing algorithm comprises Fourier transform and cross correlation algorithm.
9. The demodulation method for the sensing system based on the static pressure and sound pressure dual-parameter measurement of the Fabry-Perot etalon according to claim 5, wherein the k value in the step 2) is 2.66 x 10 -9 。
10. The demodulation method for the sensing system based on the dual parameter measurement of the static pressure and the acoustic pressure of the Fabry-Perot etalon according to claim 5, wherein the acoustic pressure parameter information comprises acoustic pressure frequency and acoustic pressure amplitude.
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