Optical fiber sensor of multi-parameter response mechanism based on cascaded FFPI cavity

Abstract

An optical fiber sensor of a multi-parameter response mechanism based on a cascade FFPI cavity comprises a first ceramic tube and a second ceramic tube arranged in the first ceramic tube in a sleeved mode, a first sapphire wafer is embedded in the inner bottom of the first ceramic tube, and a second sapphire wafer is arranged at the end, stretching into the first ceramic tube, of the second ceramic tube. An FFPI-1 cavity is formed between the first sapphire wafer and the second sapphire wafer; a pure silica optical fiber is arranged in the second ceramic tube, an optical fiber core is wrapped in the pure silica optical fiber, and an FFPI-2 cavity is formed between the end, close to the second sapphire wafer, of the pure silica optical fiber in the second ceramic tube and the second sapphire wafer; an FFPI-3 cavity is also arranged in the pure silica optical fiber positioned in the second ceramic tube; according to the invention, crosstalk perception among different parameters is quantitatively analyzed according to sensitive characteristic equations of different measurement parameters under the action of high temperature and multi-physical field coupling, a multi-parameter superposition response model and a crosstalk elimination model are established, and high temperature resistance, large strain, high pressure and high measurement accuracy are realized by combining sapphire and ceramic tube high temperature resistant materials.

Description

Technical Field

[0001] The invention relates to the field of optical fiber sensing technology, and in particular to an optical fiber sensor based on a multi-parameter response mechanism of a cascaded FFPI cavity. Technical Background

[0002] Fiber optic sensing technology has the characteristics of high temperature resistance, corrosion resistance, and anti-electromagnetic interference, and has important application prospects in high-end equipment such as aircraft engines, hypersonic engines, and large gas turbines. Taking aircraft engines as an example, the load-bearing conditions of their high-temperature flow channels are very complex. In addition to withstanding high temperatures of 1200°C and above, they also need to withstand the combined effects of high pressure, thermal stress deformation, and other loads, which can easily cause a variety of failures. These failures can often be monitored by measuring key parameters such as high temperature, strain, and gas pressure. Therefore, the real-time online monitoring of key parameters such as temperature, strain, and pressure in the high-temperature flow channel of the engine can provide an important basis for ensuring the safe operation of the engine and judging the working status of the engine. It also provides important data support for engine design and power performance evaluation.

[0003] Among the existing measurement methods, non-contact measurement methods such as infrared radiation, temperature-indicating paint method for measuring high temperature, digital image correlation method, phosphorescence method for measuring strain, and pressure tube method for measuring pressure are difficult to achieve real-time measurement in the high-temperature flow channel of an aircraft engine with complex structure and narrow space. Electrical contact measurement methods such as resistive sensors are easily interfered by corrosive gases and electromagnetic effects, and are difficult to withstand ultra-high temperatures of 1200°C. The demand for simultaneous measurement of multiple parameters will significantly increase the complexity of electrical sensor leads, bringing hidden dangers to the operation of aircraft engines. In recent years, the development of fiber-optic integrated sensors has provided new ideas for the simultaneous measurement of multiple key parameters in high-temperature flow channels. Through the compact integration of composite sensing microstructures, in-situ sensing of multiple parameters to be measured can be achieved simultaneously. Compared with fiber Bragg Gratings (FBG), Mach–Zehnder interferometer (MZI) and other structures, fiber Fabry-Perot interferometer (FFPI) has the characteristics of reflective sensing, miniaturized cascade structure, and large spectral effective bandwidth. It can meet the development needs of miniaturization, lightweight and high-precision sensors and has important research value.

[0004] Quartz optical fiber has the advantages of excellent optical properties, high temperature resistance, and mature preparation technology, and is suitable for the development of high-performance integrated sensors. At present, most of the research on quartz optical fiber FFPI focuses on single-parameter or dual-parameter sensing, and it is difficult to achieve simultaneous measurement of high temperature, strain, and pressure. At a high temperature of 900°C, crystal precipitation begins to appear inside the quartz optical fiber material, destroying the consistency of its microstructure, resulting in increased brittleness and easy damage. Studies have shown that the tensile limit of quartz optical fiber after high-temperature annealing is only 3400με, which cannot meet the measurement requirements of 15000με large strain and 5MPa high pressure of aircraft engines.

[0005] Patent application "A multi-core optical fiber distributed sensing system and measurement method"

[0006] (CN116539189A) uses Raman distributed fiber optic sensing technology to achieve distributed temperature and bending measurement, uses a wavelength division multiplexer to divide Raman scattered light into Stokes light and anti-Stokes light, demodulates temperature data through anti-Stokes light, and demodulates bending data from Stokes light. This solution directly demodulates temperature from anti-Stokes light, and the method of equivalent bending loss to bending detection results reduces the temperature detection accuracy of the sensing system and the accuracy of bending measurement. Summary of the invention

[0007] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a high-temperature and high-pressure strain optical fiber integrated sensor based on the multi-parameter response mechanism of a cascaded FFPI (Fiber Fabry-Perot Interferometer) cavity, which utilizes the corresponding reflection interference spectrum generated when the length of the FFPI cavity changes under different assembly conditions, so that the cascaded FFPI cavity can achieve parametric response and crosstalk elimination under the action of multiple physical fields, thereby realizing simultaneous and accurate perception of temperature, strain and pressure.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A fiber optic sensor based on a multi-parameter response mechanism of a cascaded FFPI cavity comprises a No. 1 ceramic tube 1 and a No. 2 ceramic tube 2 sleeved in the No. 1 ceramic tube 1, wherein a No. 1 sapphire wafer 6 is embedded in the bottom of the No. 1 ceramic tube 1, a No. 2 sapphire wafer 8 is arranged at one end of the No. 2 ceramic tube 2 extending into the No. 1 ceramic tube 1, and a FFPI-1 cavity 7 is formed in the No. 1 ceramic tube 1 and between the No. 1 sapphire wafer 6 and the No. 2 sapphire wafer 8; a pure quartz optical fiber 3 is arranged in the No. 2 ceramic tube 2, and an optical fiber core 4 is wrapped inside the pure quartz optical fiber 3, and a FFPI-2 cavity 9 is formed in the No. 2 ceramic tube 2 and between one end of the pure quartz optical fiber 3 close to the No. 2 sapphire wafer 8 and the No. 2 sapphire wafer 8; and a FFPI-3 cavity 10 is also arranged inside the pure quartz optical fiber 3 located in the No. 2 ceramic tube.

[0010] The wall of the No. 1 ceramic tube 1 is provided with an air hole 5 connected to the FFPI-1 cavity 7 .

[0011] The pure quartz optical fiber 3 is fixedly connected to the inner wall of the No. 2 ceramic tube 2 .

[0012] The second ceramic tube 2 is slidably connected relative to the first ceramic tube 1 .

[0013] The maximum deformation of the second sapphire wafer 8 is less than 0.3 times of its thickness.

[0014] The cavity lengths of the FFPI-1 cavity 7 and the FFPI-2 cavity 9 will change with temperature, while the cavity length of the FFPI-3 cavity 10 will only change with temperature. The relationship between temperature and cavity length is as follows:

[0015]

[0016]

[0017] Where: T is the measured temperature; T0 is the initial temperature; α q is the thermal expansion coefficient of pure quartz optical fiber 3; α s is the thermal expansion coefficient of the material being tested, ΔL FFPI-3-T is the length change of FFPI-3 cavity 10 caused by temperature change; ΔL FFPI-2-T ΔL is the change in length of FFPI-2 cavity 9 caused by temperature change; FFPI-1-T is the change in length of FFPI-1 cavity 7 caused by temperature change; They respectively represent the lengths of the FFPI-1 cavity 7, the FFPI-2 cavity 9 and the FFPI-3 cavity 10 at the initial temperature T0.

[0018] The air pressure in the FFPI-1 cavity 7 is made consistent with the external air pressure to be measured through the air hole 5; the pressure difference formed by the external air pressure to be measured and the air pressure in the FFPI-2 cavity 9 causes the second sapphire wafer 8 to deform, and the cavity length of the FFPI-2 cavity 9 changes accordingly.

[0019] There is a linear relationship between the pressure difference formed by the external pressure to be measured and the pressure in the FFPI-2 cavity 9 and the maximum deformation at the center of the second sapphire wafer 8, which is expressed as:

[0020]

[0021] Where P 气 Indicates the external air pressure, P FFPI-2represents the internal pressure of FFPI-2 cavity 9, b represents the thickness of the second sapphire wafer 8, r represents the effective radius of the second sapphire wafer 8, δ represents the Poisson's ratio of the second sapphire wafer 8, E is the elastic modulus of the second sapphire wafer 8, Δd is the deformation at the center of the second sapphire wafer 8, that is, the change in the length of the FFPI-2 cavity 9.

[0022] The change in the length of the FFPI-1 cavity 7 is only related to the strain. At this time, the strain value of the FFPI-1 cavity 7 is expressed as:

[0023]

[0024] Where, ΔL FFPI-1 is the total deformation of cavity 7 of FFPI-1, ΔL FFPI-1 After subtracting the change in cavity length ΔL of FFPI-1 cavity 7 due to temperature change FFPI-1-T After calculating the cavity length change Δd due to the pressure change, the strain value at cavity 7 of FFPI-1 is obtained by comparing it with the length of cavity 7 of FFPI-1 at the initial temperature T0.

[0025] The FFPI-2 cavity 9 and the FFPI-3 cavity 10 inside the pure quartz optical fiber 3 are formed by femtosecond laser processing.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses pure quartz optical fiber for sensing. By cascading multiple FFPI cavities and analyzing and designing them according to the response characteristics of each FFPI cavity to different physical parameters, accurate perception of temperature, strain, and pressure is achieved simultaneously.

[0028] 2. The present invention uses a nested ceramic sleeve, the sliding range of which is not limited by the tension and compression limits of the optical fiber material, and can achieve measurement of a very large strain range.

[0029] 3. The present invention utilizes the high hardness and high melting point characteristics of sapphire material to enable the sensor to meet the measurement requirements of ultra-high pressure.

[0030] 4. The present invention uses ceramic materials and integrates the sensing part, which can protect the sensing part under ultra-high temperature conditions, thereby realizing temperature measurement in an ultra-high temperature environment.

[0031] 5. Through the response mechanism of the multi-parameter optical fiber sensor of the present invention under the action of multiple physical fields with different air pressure, temperature and stress conditions, multi-parameter sensing and crosstalk elimination are realized, solving the problem of multi-parameter sensing crosstalk, so that the sensor of the present invention can accurately measure the temperature, pressure and strain of the structure under any multi-physical field conditions.

[0032] In summary, the present invention integrates a pure quartz optical fiber sensor with a ceramic tube structure and combines it with femtosecond laser etching technology to solve the problem of crosstalk perception between temperature, strain, and pressure under the coupling of multiple physical fields, and realizes the simultaneous and precise measurement of temperature, strain, and pressure under ultra-high temperature, large strain, and high pressure conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the sensor structure designed for the present invention.

[0034] Figure 2 Schematic diagram of the sensor optical signal transmission of the present invention.

[0035] Figure 3 A multi-parameter sensing and crosstalk cancellation model designed for the present invention.

[0036] Figure 4 Schematic diagram of the simulation model of the structure designed by the present invention.

[0037] Figure 5 The length variation curve of each FFPI cavity under different loading conditions in the simulation analysis of the present invention is shown in FIG. Figure 5 (a) is the length change of each FFPI during the application of tension and airflow, Figure 5 (b) The length change of each FFPI at different temperatures.

[0038] In the figure: 1. Ceramic tube No. 1; 2. Ceramic tube No. 2; 3. Pure quartz optical fiber; 4. Optical fiber core; 5. Air hole; 6. Sapphire wafer No. 1; 7. FFPI-1 cavity; 8. Sapphire wafer No. 2; 9. FFPI-2 cavity; 10. FFPI-3 cavity; 11. Incident light; 12. Reflected light; 13. Air flow inflow surface; 14. Air flow outflow surface; 15. Air domain outside the structure; 16. Air hole; 17. Optical fiber of the non-sensing part of the sensor; 18. Heating area; 19. The surface of the structure applying tension; 20. Structure; 21. FFPI part of the sensor. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0040] like Figure 1As shown, a fiber optic sensor based on a multi-parameter response mechanism of a cascaded FFPI cavity comprises a No. 1 ceramic tube 1 and a No. 2 ceramic tube 2 sleeved in the No. 1 ceramic tube 1, wherein a No. 1 sapphire wafer 6 is embedded in the bottom of the No. 1 ceramic tube 1, and a No. 2 sapphire wafer 8 is provided at one end of the No. 2 ceramic tube 2 extending into the No. 1 ceramic tube 1, and a FFPI-1 cavity 7 is formed in the No. 1 ceramic tube 1 and between the No. 1 sapphire wafer 6 and the No. 2 sapphire wafer 8; a pure quartz optical fiber 3 is provided in the No. 2 ceramic tube 2, and an optical fiber core 4 is wrapped inside the pure quartz optical fiber 3, and a FFPI-2 cavity 9 is formed in the No. 2 ceramic tube 2 and between one end of the pure quartz optical fiber 3 close to the No. 2 sapphire wafer 8 and the No. 2 sapphire wafer 8; and a FFPI-3 cavity 10 is also provided inside the pure quartz optical fiber 3 located in the No. 2 ceramic tube.

[0041] The wall of the No. 1 ceramic tube 1 is provided with an air hole 5 connected to the FFPI-1 cavity 7 .

[0042] The pure quartz optical fiber 3 is fixedly connected to the inner wall of the No. 2 ceramic tube 2 .

[0043] The second ceramic tube 2 is slidably connected relative to the first ceramic tube 1 .

[0044] The FFPI-2 cavity 9 and the FFPI-3 cavity 10 inside the pure quartz optical fiber 3 are formed by femtosecond laser processing.

[0045] like Figure 2 As shown, the incident light signal is emitted from the pure quartz optical fiber 3 along the direction of the internal optical fiber core 4 away from the No. 1 ceramic tube 1, and is transmitted through the FFPI-3 cavity 10, the FFPI-2 cavity 9, and the FFPI-1 cavity 7 in sequence, and generates corresponding reflection interference spectra according to the length changes of the FFPI-3 cavity 10, the FFPI-2 cavity 9, and the FFPI-1 cavity 7 under different conditions.

[0046] Multi-parameter sensing and crosstalk cancellation models such as Figure 3 The structure proposed by the present invention is subjected to finite element analysis simulation, and the simulation model is shown as follows: Figure 4As shown, the integrated optical fiber sensor was modeled in the "ANSYS Workbench" software, and the "FluidFlow (Fluent)", "Steady-State Thermal (ANSYS)" and "Static Structural (ANSYS)" modules were used to carry out fluid-heat-solid coupling simulations to observe the response mechanism of the integrated optical fiber sensor under different air pressure, temperature and stress conditions. The material of the structure 20 to be tested in the model is a high-temperature resistant nickel alloy. The size of the structure 20 to be tested is 100 times the size of the sensor FFPI part 21. An air domain 15 is provided outside the structure to be tested, and an airflow is provided. The airflow flows in from the airflow inlet surface 13, passes through the structure to be tested, and flows out from the airflow outlet surface 14. First, air pressure is applied to the structure 20 by the airflow, and the applied air pressure starts from zero and increases by 10 each time. 4 Pa up to 10 5 The structure to be tested is provided with an air hole 16, which connects the external air space 15 and the FFPI-1 cavity 7 inside the integrated optical fiber sensor. 5 On the basis of Pa being constant, a tensile force is applied to the right end face 19 of the structure, and the tensile force increases by 10N each time from zero to 100N. The length changes of FFPI-1 cavity 7, FFPI-2 cavity 9 and FFPI-3 cavity 10 during the changes of air pressure and tensile force are shown in the following figure. Figure 5 (a). Then, the pressure is maintained at 10 5 Pa and a tensile force of 100N, a temperature load is applied to the heating area 18, and the applied temperature is increased from 22°C (the initial temperature of the structure) to 42°C with a gradient of 2°C. The cavity length changes of FFPI-1 cavity 7, FFPI-2 cavity 9 and FFPI-3 cavity 10 under different temperature load conditions are shown in the figure. Figure 5 (b) as shown.

[0047] The length changes of FFPI-1 cavity 7, FFPI-2 cavity 9 and FFPI-3 cavity 10 under the influence of different physical parameters in the simulation are shown as follows Figure 5 The measurement results of FFPI-3 cavity 10 are used to compensate the temperature of FFPI-1 cavity 7 and FFPI-2 cavity 9 to eliminate temperature crosstalk. The air pressure of FFPI-1 cavity 7 is compensated based on the compensated measurement results of FFPI-2 cavity 9 to eliminate air pressure crosstalk, and ultimately achieve simultaneous and accurate perception of temperature, strain, and pressure.

[0048] When the temperature changes, the lengths of the FFPI-1 cavity 7, FFPI-2 cavity 9 and FFPI-3 cavity 10 in the cascaded FFPI sensor structure will change accordingly:

[0049]

[0050] Where: T is the measured temperature; T0 is the initial temperature; αq is the thermal expansion coefficient of pure quartz optical fiber 3; α s is the thermal expansion coefficient of the material being tested, ΔL FFPI-3-T is the length change of FFPI-3 cavity 10 caused by temperature change; ΔL FFPI-2-T ΔL is the change in length of FFPI-2 cavity 9 caused by temperature change; FFPI-1-T is the change in length of FFPI-1 cavity 7 caused by temperature change; They respectively represent the lengths of the FFPI-1 cavity 7, the FFPI-2 cavity 9 and the FFPI-3 cavity 10 at the initial temperature T0.

[0051] According to the structural design of the sensor, the FFPI-1 cavity 7 will also change with the changes of the pressure and strain to be measured, the FFPI-2 cavity 9 will also change with the changes of the pressure to be measured, and the FFPI-3 cavity 10 is only related to the temperature, so the FFPI-3 cavity 10 is used for temperature measurement. The FFPI-2 cavity 9 temperature characteristic in formula (2) will be used for temperature compensation when the FFPI-2 cavity 9 measures the air pressure, and the FFPI-1 cavity 7 temperature characteristic in formula (3) will be used for temperature compensation when the FFPI-1 cavity 7 measures the strain.

[0052] When the maximum deformation of the second sapphire wafer 8 is less than 0.3 times of the thickness, there is a linear relationship between the change in external pressure on the second sapphire wafer 8 and the maximum deformation at its center, which can be expressed as:

[0053]

[0054] Where P 气 Indicates the external air pressure, P FFPI-2 represents the internal pressure of FFPI-2 cavity 9, b represents the thickness of No. 2 sapphire wafer 8, r represents the effective radius of No. 2 sapphire wafer 8, δ represents the Poisson's ratio of No. 2 sapphire wafer 8, E is the elastic modulus of No. 2 sapphire wafer 8, Δd is the deformation at the center of No. 2 sapphire wafer 8, that is, the change in the length of FFPI-2 cavity 9. According to the structural design of the sensor, in addition to the influence of temperature, FFPI-1 cavity 7 will also change with the change of the strain to be measured. At this time, FFPI-2 cavity 9 is only related to air pressure. FFPI-1 cavity 7 is connected to the outside air through the pores, and the air pressure inside the cavity is kept consistent with the outside. The Δd obtained in formula (4) will be used for air pressure compensation during strain measurement of FFPI-1 cavity 7.

[0055] The change in the length of cavity 7 of FFPI-1 is only related to the strain. At this time, the strain value measured in cavity 7 of FFPI-1 can be expressed as:

[0056]

[0057] Where ΔLFFPI-1 is the total deformation of cavity 7 of FFPI-1, ΔL FFPI-1 After subtracting the cavity length of FFPI-1 cavity 7 due to temperature and pressure changes, the strain value of the structure is obtained by comparing it with the length of FFPI-1 cavity 7 at the initial temperature T0.

[0058] Compared with the prior art, the present invention cleverly combines the ceramic tube structure and pure quartz optical fiber to construct multiple FFPI cavities that can eliminate crosstalk with each other through the measured data; the optical fiber etched with femtosecond laser technology can simultaneously and accurately measure data under conditions of higher temperature, greater strain, and higher pressure, while using the ceramic tube structure to protect the multiple FFPI cavities of the measured parameters.

Claims

1. An optical fiber sensor based on a multi-parameter response mechanism of a cascaded FFPI cavity, comprising a first ceramic tube (1) and a second ceramic tube (2) sleeved in the first ceramic tube (1), characterized in that: A No. 1 sapphire wafer (6) is embedded in the bottom of the No. 1 ceramic tube (1); a No. 2 sapphire wafer (8) is provided at one end of the No. 2 ceramic tube (2) extending into the No. 1 ceramic tube (1); a FFPI-1 cavity (7) is formed in the No. 1 ceramic tube (1) and between the No. 1 sapphire wafer (6) and the No. 2 sapphire wafer (8); a pure quartz optical fiber (3) is provided in the No. 2 ceramic tube (2); an optical fiber core (4) is wrapped inside the pure quartz optical fiber 3; a FFPI-2 cavity (9) is formed in the No. 2 ceramic tube (2) and between one end of the pure quartz optical fiber (3) close to the No. 2 sapphire wafer (8) and the No. 2 sapphire wafer (8); and a FFPI-3 cavity (10) is also provided inside the pure quartz optical fiber (3) located in the No. 2 ceramic tube.

2. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The wall of the No. 1 ceramic tube (1) is provided with an air hole (5) connected to the FFPI-1 cavity (7).

3. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The pure quartz optical fiber (3) is fixedly connected to the inner wall of the No. 2 ceramic tube (2).

4. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The second ceramic tube (2) is slidably connected relative to the first ceramic tube (1).

5. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The maximum deformation of the second sapphire wafer (8) is less than 0.3 times its thickness.

6. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The cavity lengths of the FFPI-1 cavity (7) and the FFPI-2 cavity (9) will change with temperature, while the cavity length of the FFPI-3 cavity (10) will only change with temperature. The relationship between temperature and cavity length is as follows: Where: T is the measured temperature; T0 is the initial temperature; α q is the thermal expansion coefficient of pure quartz optical fiber (3); α s is the thermal expansion coefficient of the material being tested, ΔL FFPI-3-T ΔL is the change in length of the FFPI-3 cavity (10) caused by temperature change; FFPI-2-T ΔL is the change in length of the FFPI-2 cavity (9) caused by temperature change; FFPI-1-T is the change in length of the FFPI-1 cavity (7) caused by temperature change; They respectively represent the lengths of the FFPI-1 cavity (7), the FFPI-2 cavity (9) and the FFPI-3 cavity (10) at the initial temperature T0.

7. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The FFPI-1 cavity (7) makes the air pressure inside the cavity consistent with the external air pressure to be measured through the air hole (5); the pressure difference formed by the external air pressure to be measured and the air pressure inside the FFPI-2 cavity (9) causes the second sapphire wafer (8) to deform, and the cavity length of the FFPI-2 cavity (9) changes accordingly.

8. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 7, characterized in that: There is a linear relationship between the pressure difference formed by the external pressure to be measured and the pressure in the FFPI-2 cavity (9) and the maximum deformation at the center of the second sapphire wafer (8), which can be expressed as: Where P 气 Indicates the external air pressure, P FFPI-2 represents the internal pressure of the FFPI-2 cavity (9), b represents the thickness of the second sapphire wafer (8), r represents the effective radius of the second sapphire wafer (8), δ represents the Poisson's ratio of the second sapphire wafer (8), E is the elastic modulus of the second sapphire wafer (8), and Δd is the deformation at the center of the second sapphire wafer (8), that is, the change in the cavity length of the FFPI-2 cavity (9).

9. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The change in the length of the FFPI-1 cavity (7) is only related to the strain. At this time, the strain value of the FFPI-1 cavity (7) is expressed as: In the formula, ΔL FFPI-1 is the total deformation of the FFPI-1 cavity (7), ΔL FFPI-1 After subtracting the change in cavity length ΔL due to temperature change in the FFPI-1 cavity (7), FFPI-1-T After calculating the cavity length change Δd due to the pressure change, the strain value at the FFPI-1 cavity (7) is obtained by comparing it with the length of the FFPI-1 cavity (7) at the initial temperature T0.

10. The optical fiber sensor based on the multi-parameter response mechanism of the cascaded FFPI cavity according to claim 1, characterized in that: The FFPI-2 cavity (9) and the FFPI-3 cavity (10) inside the pure quartz optical fiber (3) are formed by femtosecond laser processing.

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