Fiber grating pressure sensor device

Abstract

The application belongs to the technical field of pressure measurement, and relates to a high-precision high-pressure fiber grating pressure sensor, the main structure of which comprises an outer cylinder sleeved outside a thin-walled cylinder and a pi-phase shift grating arranged on the thin-walled cylinder, the improved sensitive structure thin-walled cylinder is used as a pressure conversion element, the outer cylinder is used as a protection structure, the pi-phase shift grating adopting laser sweep frequency technology and cross-correlation algorithm as an interrogation system is used as a pressure sensing element, the wide measurement range and high sensitivity requirements of deep-sea pressure measurement are met, the structure is more reasonable, has high portability, practicality and flexibility, can be expanded for multi-parameter measurement and multipoint measurement, and is particularly suitable for pressure measurement occasions requiring a large range and high precision, such as seawater depth measurement and oil and gas pipeline measurement, while meeting the wide measurement range and high resolution requirements of deep-sea pressure measurement, the fiber grating pressure sensor is easy to integrate, has strong expandability, is small in size, good in linearity, low in cost and good in stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pressure measurement, and particularly relates to a high-precision high-pressure fiber grating pressure sensor, which is particularly suitable for pressure measurement environments that need to consider both a large range and high precision, including seawater depth measurement, oil and gas pipeline measurement, etc. BACKGROUND

[0002] The temperature, salinity and depth of seawater, referred to as temperature-salinity-depth, are the three most basic and important physical quantities of the marine environment. The traditional temperature-salinity-depth measurement method mainly uses a temperature-salinity-depth profiler (CTD), a disposable temperature-salinity-depth instrument (XCTD), an Argo buoy, a submerged buoy and other equipment. In recent years, with the development and progress of marine exploration technology, new types of underwater observation equipment such as underwater gliders (Glider) and underwater autonomous underwater vehicles (AUV) have gradually emerged. Pressure measurement plays a very important role in these devices: firstly, the environmental pressure of seawater can provide parameters for physical quantities such as seawater density and seawater sound speed, and secondly, according to the conversion experience formula of seawater pressure and seawater depth, the seawater pressure can be converted into seawater depth, which can be used as the vertical spatial coordinate of the observation instrument.

[0003] The pressure sensors in the prior art mainly include quartz resonant pressure sensors, silicon piezoresistive pressure sensors and strain gauge pressure sensors: the quartz resonant pressure sensor has high precision and good stability, the range can reach 11000 meters, the precision can reach 0.015% FS (Full Scale), the silicon piezoresistive pressure sensor has small size and low cost, the range can reach 6000 meters, and the precision can reach 0.05% FS, and the strain gauge pressure sensor has low cost, simple production and wide application, the range can reach 11000 meters, and the precision is 0.1% FS.

[0004] However, it is expensive, fragile and bulky; the silicon piezoresistive pressure sensor has small size and low cost, the range can reach 6000 meters, and the precision can reach 0.05% FS; the strain gauge pressure sensor has low cost, simple production and wide application, the range can reach 11000 meters, and the precision is 0.1% FS. Compared with the above three electrical pressure sensors, the fiber grating pressure sensor has small size, low cost, good stability, high precision, good integration, multi-parameter measurement and strong anti-electromagnetic interference ability, and can be used in strong electromagnetic interference, humid and other harsh environments.

[0005] Fiber Bragg grating pressure sensor is a mature technology, stable performance and widely used fiber sensor device, suitable for distributed measurement, easy to expand to multi-parameter and multi-point measurement. However, the pressure sensitivity of fiber Bragg grating itself is low, about 3 pm / MPa, the pressure measurement range is 0-70 Mpa, which cannot be applied in practice. In order to improve the pressure sensitivity of fiber Bragg grating, the sensitization structure emerges as the times require, mainly including diaphragm type, thin-walled cylinder type, bourdon tube type, metal bellows type, polymer coating type and spring tube type. Diaphragm type fiber Bragg grating pressure sensor often needs to cooperate with metalized packaging, the manufacturing process is complex and the cost is high. Spring tube type fiber Bragg grating pressure sensor needs reliable cooperation between parts, otherwise it is easy to appear zero drift problem. Bourdon tube type and bellows type fiber Bragg grating pressure sensor has large size and low natural frequency, which is not suitable as a sensitive element of dynamic pressure sensor. Polymer type fiber Bragg grating pressure sensor has aging and creep problems during long-term use, and is not suitable for humid environment such as seawater. Among them, thin-walled cylinder type fiber Bragg grating pressure sensor has wide measurement range and good linearity, easy to process and place temperature compensation grating, which can improve the pressure measurement accuracy.For example, Chinese patent application 201610330752.3 discloses a high-temperature-resistant fiber grating pressure sensor, which comprises a fiber grating. The pressure sensor further comprises a thin-walled cylinder, a protective sleeve and an oil inlet chuck. The thin-walled cylinder is located in the protective sleeve, the fiber grating is attached to the outer surface of the thin-walled cylinder, the oil inlet chuck is sealingly connected with the protective sleeve, the oil inlet chuck is connected with the thin-walled cylinder, the left end portion of the thin-walled cylinder is designed as a hollow structure, the right end portion of the thin-walled cylinder is designed as a solid structure, the axial length of the hollow portion of the left end of the thin-walled cylinder is equal to the axial length of the solid portion of the right end of the thin-walled cylinder, the tail portion of the solid portion of the right end of the thin-walled cylinder is designed with a circular boss, at least one through hole communicating with the cavity of the protective sleeve is arranged on the circular boss, the material of the thin-walled cylinder is LY16 hard aluminum alloy, the oil inlet chuck is sealingly connected with the protective sleeve, that is, the oil inlet chuck is threadedly connected with the protective sleeve, and high-temperature glue is coated at the threadedly connected position, the materials of the protective sleeve and the oil inlet chuck are both 304 stainless steel, the pressure sensor further comprises a connecting sleeve, the connecting sleeve is connected with the right end of the protective sleeve, and the material of the connecting sleeve is 304 stainless steel. Chinese patent application 202010270811.9 discloses a disposable optical fiber temperature and depth probe, which mainly comprises a flow guide head and a flow guide cover. The flow guide head is fixedly connected to the flow guide cover, and the interiors of the two form a cavity for packaging a fiber grating temperature sensor, a fiber grating pressure sensor, a fiber cable A and a lower fiber skeleton. A through hole is formed in the head of the flow guide head to facilitate the flow of water into the inner cavity. The fiber grating temperature sensor and the fiber grating pressure sensor are connected together for simultaneously and accurately measuring the temperature and depth data of the target water area. The two are fixed to the inner wall of the lower fiber skeleton and are connected with the fiber cable A. The fiber cable A is wound on the lower fiber skeleton for transmitting data to the outside world. The lower fiber skeleton is a thin-walled cylindrical structure for supporting the fiber grating temperature sensor, the fiber grating pressure sensor and the fiber cable A, and is threadedly connected to the flow guide head. The flow guide head is in the shape of an inverted circular truncated cone with a streamlined surface to reduce water resistance. After the flow guide head and the flow guide cover are fixedly connected, they form a spindle shape with thin ends and a thick middle. Three tail wings are evenly distributed on the outer wall of the flow guide cover. Each tail wing has a fold at the top to stabilize the vertical posture of the probe when it is descending. However, the thin-walled cylinder grating pressure sensor in the prior art is suitable for shallow sea pressure measurement (water depth of 2000 meters or less), and cannot meet the demand of deep-sea pressure measurement (water depth of 6000 meters or more). Because the static pressure of deep-sea water is huge, the environment is relatively stable, and the parameter change range is small, deep-sea pressure measurement requires wide measurement range and high resolution (range greater than 6000 meters of water depth, accuracy higher than 0.01% FS). Therefore, a fiber grating pressure sensing device is developed and designed for pressure measurement occasions requiring wide measurement range and high resolution. SUMMARY

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and to develop and design a fiber optic grating pressure sensing device to meet the requirements of wide measurement range and high resolution for deep-sea pressure measurement.

[0007] To achieve the above objectives, the main structure of the fiber optic pressure sensing device of the present invention includes an outer cylinder sleeved on the outside of a thin-walled cylinder, and a π-phase-shift grating disposed on the thin-walled cylinder; the outer cylinder and the thin-walled cylinder, which are in contact with each other, are disposed on a support base, and the π-phase-shift grating includes a pressure-measuring grating and a temperature-compensated grating, both of which employ laser frequency scanning technology and a cross-correlation algorithm query system.

[0008] First, set the scanning frequency of the tunable laser to cover the entire measurement range;

[0009] Then, a gas absorption cell is used as a stable frequency standard source, and the frequency difference between the resonant peak of the π-phase shift grating 11 and the gas absorption line is calculated using a cross-correlation algorithm. The resonant peak of the π-phase shift grating 11 shifts with changes in external environmental parameters (temperature, pressure, etc.).

[0010] Finally, the frequency difference was calculated using laser frequency scanning technology and cross-correlation algorithm, and the laser frequency-environmental parameter variation curve was plotted to realize the measurement of environmental parameters.

[0011] The present invention relates to a support base with pressure holes and an outer cylinder connected by matching threads, a sealing ring provided between the support base and the thin-walled cylinder, a gap between the outer cylinder and the thin-walled cylinder, a sleeve provided at the top center of the outer cylinder, and the thin-walled cylinder having a base and a cavity, with a step provided on the base.

[0012] The cavity involved in this invention has a rounded corner, a chamfered corner, or no rounded corner and chamfered corner treatment on its top. When the corner is rounded, the radius of the rounded corner is approximately equal to the inner diameter of the cavity. Compared with a thin-walled cylinder without rounded corner treatment (the top of the cavity has a flat top structure), the thin-walled cylinder with rounded corner treatment can avoid damage caused by excessive local stress at the corners of the flat top structure, thus expanding the measurement range and meeting the needs of a larger pressure measurement range. When the chamfer is chamfered, the chamfer radius is smaller than the inner diameter of the cavity.

[0013] The fiber optic grating pressure sensing device of the present invention is subjected to external pressure P. When the external pressure is applied to the inner wall of the cavity through the pressure tapping hole, the thin-walled cylinder undergoes axial and radial deformation. The π-phase shift grating is subjected to the same pressure and senses the same temperature.

[0014] The resonant peak wavelength drift of the π-phase-shifting grating is affected by the combined effects of external pressure and ambient temperature, as shown in formula (1):

[0015]

[0016] Where, λ B Δλ is the center wavelength of the π-phase shift grating 11. B P represents the change in the resonant peak wavelength of the π-phase-shifted grating. e ε is the photoelastic coefficient of the π-phase-shifting grating. a For the axial strain of the π-phase-shifting grating, the strain in a typical single-mode silica fiber is 0.21, α t η is the thermal expansion coefficient of the π-phase-shifting grating, η is the thermo-optic coefficient of the π-phase-shifting grating, and ΔT is the change in ambient temperature.

[0017] Calibrating the pressure and temperature coefficients of the π-phase-shift grating can effectively solve the problem of cross-sensitivity between temperature and pressure, and improve the accuracy of pressure measurement. Temperature compensation is performed using the matrix method, see formula (2):

[0018]

[0019] Where, Δλ Bπ-P k Tπ-P and k Pπ-P These represent the center wavelength offset, temperature coefficient, and pressure coefficient of the pressure grating, respectively, Δλ. Bπ-T k Tπ-T and k Pπ-T These are the center wavelength offset of the temperature measuring grating, the temperature coefficient, and the pressure coefficient, respectively.

[0020] The accuracy and resolution of the fiber optic grating pressure sensing device of the present invention depend on the demodulation accuracy and demodulation resolution of the interrogation system for the resonant wavelength of the π-phase-shift grating, respectively.

[0021] For the calculation of accuracy and resolution, please refer to formula (3):

[0022]

[0023] For the calculation of resolution, please refer to formula (4):

[0024]

[0025] Where, Δλ Accuracy To improve the wavelength demodulation accuracy of the query system, Δλ Resolution For the wavelength demodulation resolution of the query system, v r Let be the radial strain of the thin-walled cylinder, Ac be the measurement accuracy, Re be the measurement resolution, and R be the inner radius of the thin-walled cylinder.

[0026] Compared with existing technologies, this invention uses an improved sensitive-enhancing thin-walled cylinder as the pressure conversion element, an outer cylinder as the protective structure, and a π-phase-shift grating with laser frequency scanning technology and cross-correlation algorithm as the interrogation system as the pressure sensing element. It simultaneously meets the wide measurement range and high sensitivity requirements of deep-sea pressure measurement. The structure is more rational, highly portable, practical, and flexible, and can be expanded to multi-parameter and multi-point measurements. It is particularly suitable for pressure measurement applications requiring both large range and high precision, such as seawater depth measurement and oil and gas pipeline measurement. Its simple structure, while meeting the wide measurement range and high resolution requirements of deep-sea pressure measurement, also offers advantages such as easy integration, strong scalability, small size, good linearity, low cost, and good stability. Attached image description:

[0027] Figure 1 This is a schematic diagram of the main structure of the present invention.

[0028] Figure 2 This is a schematic diagram of the thin-walled cylinder involved in the present invention.

[0029] Figure 3 The figure shows the finite element analysis simulation of the thin-walled cylinder of the present invention at 110 MPa.

[0030] Figure 4 This is a schematic diagram of the strain of the π-phase-shifting grating under pressure according to the present invention.

[0031] Figure 5 This is a schematic diagram illustrating the temperature coefficient calibration of the π-phase-shifting grating involved in the present invention.

[0032] Figure 6 This is a schematic diagram illustrating the pressure coefficient calibration of the π-phase-shifting grating involved in the present invention.

[0033] Figure 7 This is a schematic diagram of the high-pressure stability test results involved in this invention.

[0034] Figure 8 This is a schematic diagram of the response time test results involved in the present invention. Detailed implementation method:

[0035] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0036] Example 1:

[0037] The main structure of a fiber optic grating pressure sensing device involved in this embodiment is as follows: Figure 1 and Figure 2As shown, it includes a pressure-inlet hole 1, a support base 2, an outer cylinder 3, a thin-walled cylinder 4, a thread 5, a sealing ring 6, a sleeve 7, a base 8, a cavity 9, a step 10, and a π-phase-shifting grating 11. The support base 2, which has a pressure-inlet hole 1 in the center, is equipped with an outer cylinder 3 and a thin-walled cylinder 4. The support base 2 and the outer cylinder 3 are connected by matching threads 5. A sealing ring 6 is provided between the support base 2 and the thin-walled cylinder 4. The outer cylinder 3 is sleeved on the outside of the thin-walled cylinder 4 and is fixed by pressing the edge. There is a gap between the two. A sleeve 7 is provided at the top center of the outer cylinder 3. The hollow thin-walled cylinder 4 has a base 8 and a cavity 9. A step 10 is provided on the base 8. A π-phase-shifting grating 11 is provided on the outer wall of the thin-walled cylinder 4.

[0038] In this embodiment, both the outer cylinder 3 and the base 8 are made of metal. The pressing contact fixing method between the outer cylinder 3 and the thin-walled cylinder 4 has the advantages of low stress concentration, good stress distribution uniformity, and high stability compared to the metal bolt fixing method. The top outer side of the thin-walled cylinder 4 is chamfered, and the chamfer radius is less than or equal to the inner diameter of the cavity 9. The sealing ring 6 is an O-ring. The sleeve 7 is made of rubber and is used to protect and oriented the grating. The hydraulic contact area at the center of the base 8 is chamfered to reduce the stress concentration effect caused by sharp inflection points and increase the pressure measurement range. The cross-section of the cavity 9 is circular, and the longitudinal section is rectangular. The stress distribution is isotropic along the circumferential direction, which can prevent failure caused by local stress concentration and expand the measurement range. The top of the cavity 9 is rounded, with the radius of the rounded corner being less than or equal to the inner diameter of the cavity 9. The step 10 is an arc-shaped structure, which can effectively increase the thickness of the base 8, enhance the bending stiffness of the thin-walled cylinder 4, reduce the size of the thin-walled cylinder 4, prevent local stress concentration in the thin-walled cylinder 4, and improve the compressive strength. The π-phase shift grating 11 consists of two π-phase shift gratings with similar resonant peak wavelengths after secondary annealing, including a pressure measuring grating 12 and a temperature-compensated grating 13 that are parallel to each other. The temperature-compensated grating 13 provides temperature compensation for the pressure measuring grating 12. The pressure measuring grating 12 and the temperature-compensated grating 13 are symmetrical about the center position of the cavity 9. They are set on the thin-walled cylinder 4 through an axially arranged fiber positioning groove on the side wall of the thin-walled cylinder 4. The shape of the fiber positioning groove includes, but is not limited to, a spiral shape.

[0039] Example 2:

[0040] The usage process of the fiber optic grating pressure sensing device described in this embodiment includes three steps: assembly, pressurization, and testing.

[0041] (1) Assembly

[0042] First, the π-phase shift gratings 11 from the same batch are placed in a high-low temperature cycling chamber for secondary annealing for 100 hours. Two π-phase shift gratings with similar resonant peak wavelengths are selected as pressure measuring grating 12 and temperature-compensated grating 13, respectively. The pressure measuring grating 12 is wound in a spiral shape on the outer wall of the thin-walled cylinder 4, and the temperature-compensated grating 13 is wound in a spiral shape with slightly different wire diameters on the outer wall of the thin-walled cylinder 4, so that the pressure measuring grating 12 and the temperature-compensated grating 13 are parallel to each other and symmetrical about the center position of the cavity 9. The transmission optical fibers of the pressure measuring grating 12 and the temperature-compensated grating 13 are led out of the thin-walled cylinder 4 through the sleeve 7 and connected to the external interrogation system.

[0043] Then, a three-dimensional model of the thin-walled cylinder 4 was created, and simulation analysis was performed in finite element analysis software. The results are as follows. Figure 3 and Figure 4 As shown, at 110 MPa, the maximum stress of the thin-walled cylinder 4 is 258 MPa, and the maximum displacement is 7.06 μm. According to Table 2 of GB / T2965-2007 Titanium and Titanium Alloy Bars, the tensile strength of TC4 titanium alloy material at room temperature is not less than 895 MPa. According to the calculation relationship between the safety factor and allowable stress of pressure vessels in GB150-1998 Steel Pressure Vessels and JB4732-1995 Steel Pressure Vessels—Analysis and Design Standard, the allowable stress of TC4 titanium alloy material is 298 MPa.

[0044] Finally, the thin-walled cylinder 4 is assembled onto the support base 2, and a sealing ring 6 is installed in the groove of the support base 2 to achieve water tightness; the outer cylinder 3 is brought into close contact with the upper surface of the base 8, and the outer cylinder 3 is screwed onto the support base 2 through the matching threads 10. The outer cylinder 3 protects the thin-walled cylinder 4 and the π-phase shift grating 11, thus achieving the encapsulation of the thin-walled cylinder 4.

[0045] (2) Pressurization

[0046] When pressurization is performed in the laboratory, the support base 2 is connected to the output end of an external piston pressure gauge via the pressure adapter 100;

[0047] If pressurization is required in the actual use environment, the fiber optic pressure sensor can be placed directly in the test condition, or a pressure adapter 100 that matches the test condition can be manufactured.

[0048] (3) Test

[0049] The temperature coefficients and pressure coefficients of the pressure-measuring grating 12 and the temperature-compensated grating 13 were calibrated respectively, and the results are as follows: Figure 5 and Figure 6 As shown, the pressure grating 12 and the temperature-compensated grating 13 exhibit good linearity in temperature and pressure response;

[0050] The fiber Bragg grating pressure sensor was subjected to a stability test under a pressure of 120 MPa, and the results are as follows: Figure 7 As shown, its stability over 3 hours is better than 0.03% FS;

[0051] The response time of the fiber Bragg grating pressure sensing device was tested using a piston-type pressure generator, and the results are as follows: Figure 8 As shown, the response time is 20ms; if a shock tube is used for testing, the response time can be improved by several orders of magnitude.

Claims

1. A fiber optic pressure sensing device, the main structure comprising an outer cylinder sleeved on the outside of a thin-walled cylinder, and a π-phase-shifting grating disposed on the thin-walled cylinder, the outer cylinder and the thin-walled cylinder being disposed on a supporting base, characterized in that, π-phase-shifting gratings include pressure-measuring gratings and temperature-compensated gratings, both employing laser frequency sweeping technology and cross-correlation algorithm query systems. First, set the scanning frequency of the tunable laser to cover the entire measurement range; Then, a gas absorption cell was used as a stable frequency standard source, and the frequency difference between the resonant peak of the π-phase shift grating and the gas absorption line was calculated using a cross-correlation algorithm. The resonant peak of the π-phase shift grating shifts with changes in external environmental parameters. Finally, the frequency difference was calculated using laser frequency scanning technology and cross-correlation algorithm, and the laser frequency-environmental parameter variation curve was plotted to realize the measurement of environmental parameters.

2. The fiber optic grating pressure sensing device according to claim 1, characterized in that, The support base with pressure inlet holes is connected to the outer cylinder by matching threads. A sealing ring is provided between the support base and the thin-walled cylinder. There is a gap between the outer cylinder and the thin-walled cylinder. A sleeve is provided at the top center of the outer cylinder. The thin-walled cylinder has a base and a cavity. A step is provided on the base.

3. The fiber optic grating pressure sensing device according to claim 2, characterized in that, The top of the cavity is rounded, chamfered, or left unrounded and unchamfered: when rounded, the radius of the rounded corner is approximately equal to the inner diameter of the cavity; when chamfered, the radius of the chamfer is smaller than the inner diameter of the cavity.

4. A fiber optic grating pressure sensing device according to claim 1 or 2, characterized in that, When subjected to external pressure P, the external pressure is applied to the inner wall of the cavity through the pressure-injection hole. The thin-walled cylinder undergoes axial and radial deformation. The π-phase-shifting grating is subjected to the same pressure and experiences the same temperature. The resonant peak wavelength drift of the π-phase-shifting grating is affected by the combined effects of external pressure and ambient temperature, as shown in formula (1): Where, λ B Δλ is the center wavelength of the π-phase-shifting grating. B P represents the change in the resonant peak wavelength of the π-phase-shifted grating. e ε is the photoelastic coefficient of the π-phase-shifting grating. a For the axial strain of the π-phase-shifting grating, the strain in a typical single-mode silica fiber is 0.21, α t η is the thermal expansion coefficient of the π-phase-shifting grating, η is the thermo-optic coefficient of the π-phase-shifting grating, and ΔT is the change in ambient temperature. The pressure coefficient and temperature coefficient of the π-phase shift grating were calibrated, and temperature compensation was performed using the matrix method, as shown in formula (2): Where, Δλ Bπ-P k Tπ-P and k Pπ-P These represent the center wavelength offset, temperature coefficient, and pressure coefficient of the pressure grating, respectively, Δλ. Bπ-T k Tπ-T and k Pπ-T These are the center wavelength offset of the temperature measuring grating, the temperature coefficient, and the pressure coefficient, respectively.

5. The fiber optic grating pressure sensing device according to claim 4, characterized in that, Accuracy and resolution depend on the demodulation accuracy and resolution of the interrogation system for the resonant wavelength of the π-phase-shift grating, respectively. For the calculation of accuracy and resolution, please refer to formula (3): For the calculation of resolution, please refer to formula (4): Where, Δλ Accuracy To improve the wavelength demodulation accuracy of the query system, Δλ Resolution For the wavelength demodulation resolution of the query system, v r Let be the radial strain of the thin-walled cylinder, Ac be the measurement accuracy, Re be the measurement resolution, and R be the inner radius of the thin-walled cylinder.

6. The fiber optic grating pressure sensing device according to claim 2, characterized in that, Both the outer cylinder and the base are made of metal. The top outer side of the thin-walled cylinder is chamfered, with the chamfer radius less than or equal to the inner diameter of the cavity. The sealing ring is an O-ring. The sleeve is made of rubber and is used to protect and orient the grating. The hydraulic contact area at the center of the base is chamfered. The cross-section of the cavity is circular, and the longitudinal section is rectangular. The stress distribution is isotropic along the circumferential direction. The top of the cavity is rounded, with the rounded corner radius less than or equal to the inner diameter of the cavity. The step is an arc-shaped structure, which effectively increases the thickness of the base, enhances the bending stiffness of the thin-walled cylinder, and reduces the size of the thin-walled cylinder. The π-phase shift grating consists of two π-phase shift gratings with similar resonant peak wavelengths after secondary annealing, including a pressure-measuring grating and a temperature-compensated grating that are parallel to each other. The temperature-compensated grating compensates for the temperature of the pressure-measuring grating. The pressure-measuring grating and the temperature-compensated grating are symmetrical about the center of the cavity and are positioned on the thin-walled cylinder through an axially arranged fiber positioning groove on the side wall of the thin-walled cylinder.

7. The fiber optic grating pressure sensing device according to claim 6, characterized in that, The usage process includes three steps: assembly, pressurization, and testing. (1) Assembly First, the π-phase shift gratings of the same batch were placed in a high-low temperature cycling chamber for secondary annealing for 100 hours. Two π-phase shift gratings with similar resonant peak wavelengths were selected as the pressure-measuring grating and the temperature-compensated grating, respectively. The pressure-measuring grating was wound in a spiral shape on the outer wall of the thin-walled cylinder, and the temperature-compensated grating was wound on the outer wall of the thin-walled cylinder, so that the pressure-measuring grating and the temperature-compensated grating were parallel to each other and symmetrical about the center of the cavity. The transmission optical fibers of the pressure-measuring grating and the temperature-compensated grating were led out of the thin-walled cylinder through a sleeve and connected to the external interrogation system. Then, a three-dimensional model of the thin-walled cylinder is created, and simulation analysis is performed in finite element analysis software; Finally, the thin-walled cylinder is assembled onto the support base, and a sealing ring is installed in the groove of the support base. Make the outer cylinder and the upper surface of the base come into close contact, and tighten the outer cylinder and the support base with matching threads; (2) Pressurization When pressurization is performed in the laboratory, the support base is connected to the output of an external piston pressure gauge via a pressure adapter. When pressurizing in a real-world environment, place the fiber optic pressure sensor directly in the test condition, or manufacture a pressure adapter that matches the test condition. (3) Test The temperature coefficients and pressure coefficients of the pressure-measuring grating and the temperature-compensated grating are calibrated respectively. The fiber optic pressure sensor was placed under a set pressure condition for stability testing. A piston-type pressure generator was used to test the response time of the fiber Bragg grating pressure sensing device.

8. The fiber optic grating pressure sensing device according to claim 7, characterized in that, When using a shock tube for testing, the response time will be improved.

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