Fiber grating pressure sensor

Abstract

The invention discloses a fiber bragg grating pressure sensor, and relates to the technical field of pressure sensors. The fiber bragg grating pressure sensor is arranged in a cavity of a shell, an auxiliary diaphragm is arranged close to a pressure interface, a main diaphragm and the auxiliary diaphragm are arranged at an interval, and a base of a variable lever mechanism tightly abuts against the main diaphragm; one end of the stressed fiber bragg grating is fixedly arranged on an output arm of the variable lever mechanism, the other end of the stressed fiber bragg grating is fixedly connected with a base of the variable lever mechanism, and the middle of the stressed fiber bragg grating is suspended, so that a dual-diaphragm-pressure transmission liquid-variable lever synergistic structure is formed, and segmented self-adaptive sensitivity and wide range can be realized; and the problem of coexistence of insufficient resolution of small signals and large impact saturation is avoided.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, and more particularly to a fiber Bragg grating pressure sensor. Background Technology

[0002] Currently, large power transformers serve as the core hub of the power grid, and their operational reliability directly affects the safety and stability of the energy system. Short circuits or electric arcs cause a sudden increase in electrodynamic force and localized heating, which may generate transient high-voltage waves in the oil, impacting the tank walls and structural components, increasing the risk of tank damage and explosion.

[0003] Current condition assessments largely rely on indirect parameters such as oil temperature and current, making it difficult to reflect the true mechanical state of critical components. Traditional electronic or metal-cased pressure sensors struggle to balance range and sensitivity, making it difficult to be compatible with both "monitoring small-amplitude daily fluctuations" and "recording large-amplitude pressure during short-circuit impacts," often resulting in saturation or insufficient resolution. These factors limit the direct online measurement of mechanical stress / pressure within transformers, hindering the provision of continuous and reliable data support for assessing the stress state of the transformer tank walls, early fault identification, and post-accident mechanism analysis. Summary of the Invention

[0004] Therefore, it is necessary to provide a fiber Bragg grating pressure sensor to address the aforementioned technical problems.

[0005] The present invention adopts the following technical solution: This invention provides a fiber Bragg grating pressure sensor, comprising: a housing, a secondary diaphragm, a primary diaphragm, a variable lever mechanism, a force-bearing fiber Bragg grating, a reference fiber Bragg grating, and a top cover; A pressure port is provided at one end of the outer casing, and the top cover is fixedly installed at the other end of the outer casing; Inside the cavity of the outer casing, the secondary diaphragm is positioned close to the pressure port, while the primary diaphragm and the secondary diaphragm are positioned at intervals. The base of the variable lever mechanism and the main diaphragm are in elastic contact with each other. As the pressure on the main diaphragm increases, the contact area between the main diaphragm and the base of the variable lever mechanism increases, triggering the fulcrum migration of the variable lever mechanism. The cavity between the main diaphragm and the sub-diaphragm, as well as between the main diaphragm and the top cover, is filled with pressure-transmitting fluid at a preset pressure, so that the stressed fiber grating is taut when the sub-diaphragm is not subjected to external pressure.

[0006] Optionally, the base of the variable lever mechanism is a conical contact element, with its small end abutting against the main diaphragm.

[0007] Optionally, the outer shell and the top cover are made of PEEK or ceramic material, the variable lever mechanism is made of POM / PEEK or carbon fiber composite material, and the pressure transmission fluid is silicone oil.

[0008] Optionally, the upper cover is provided with a retainer on the cavity side, and an optical fiber lead-out hole is opened on the side wall of the upper cover. A buffer groove is provided between the retainer and the optical fiber lead-out hole. Both the stressed fiber optic grating and the reference fiber optic grating are led out to the holder through optical fibers, and then guided through the buffer groove to the fiber optic exit hole for connection with the external demodulator. The fiber optic exit hole is equipped with a sealing cap / glue seal. The buffer groove is used to release the bending stress and thermal expansion and contraction displacement of the optical fiber, and to provide the optical fiber displacement margin and damping path under the impact load of external pressure.

[0009] Optionally, the preset pressure is 0.02MPa~0.05MPa.

[0010] Optionally, the viscosity of the silicone oil is 100 cSt to 1000 cSt.

[0011] Optionally, the diameter of the sub-diaphragm is 10mm~14mm and the thickness is 0.3mm~0.6mm; The main diaphragm has a diameter of 12mm to 18mm and a thickness of 0.6mm to 1.2mm.

[0012] The above-mentioned at least one technical solution adopted in this invention can achieve the following beneficial effects: The fiber optic pressure sensor of this invention has a secondary diaphragm located adjacent to the pressure interface within the cavity of the housing, while the primary diaphragm and secondary diaphragm are spaced apart. The base of the variable lever mechanism is in elastic contact with the primary diaphragm. One end of the force-bearing fiber optic grating is fixedly mounted on the output arm of the variable lever mechanism, and the other end is fixedly connected to the base of the variable lever mechanism with the middle part suspended. This forms a collaborative structure of "dual diaphragm - pressure-transmitting fluid - variable lever", which can achieve segmented adaptive sensitivity and wide range, avoiding the problems of insufficient small signal resolution and large impact saturation.

[0013] When the external pressure is in the low-pressure operating range, the secondary diaphragm undergoes elastic deformation first. The base contact radius of the variable lever mechanism is small and the fulcrum position is far away, resulting in a large equivalent force arm ratio. At this time, the fiber optic pressure sensor exhibits high sensitivity and high resolution, effectively capturing daily fluctuations and gradual trends, providing a data basis for health assessment and threshold tuning.

[0014] When the external pressure enters the medium pressure range, the main diaphragm begins to participate in load bearing, the equivalent stiffness of the cavity increases, the contact radius of the base of the variable lever mechanism expands accordingly, and the fulcrum moves smoothly inward toward the input end. The equivalent lever ratio decreases accordingly, the sensitivity drops to a medium level, while maintaining good linearity and dynamic response, making it suitable for transient recording in the initial stage of short-circuit impacts.

[0015] Under high-pressure impact scenarios, the main and auxiliary diaphragms work together to significantly improve the overall load-bearing stiffness, and the leverage ratio of the variable lever mechanism is further reduced to avoid sensor link saturation. This segment balances wide measurement range and recoverability, enabling the sensor to record high-amplitude transient pressure peaks and rise-edge characteristics without distortion, which can be used for accident precursor identification and mechanism deconstruction. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0017] Figure 1 This is a schematic diagram of a fiber Bragg grating pressure sensor provided by the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] Currently, traditional electronic or metal-cased pressure sensors are susceptible to power frequency and high-frequency electromagnetic interference in oil-immersed transformer environments. Metal components may introduce parasitic conductive paths and insulation hazards, and corrosion and long-term stability issues exist under insulating oil and high-temperature conditions. Furthermore, conventional sensors struggle to balance range and sensitivity, making it difficult to reconcile "monitoring small-amplitude daily fluctuations" with "recording large-amplitude pressure during short-circuit impacts," often resulting in saturation or insufficient resolution. These factors limit the direct online measurement of mechanical stress / pressure within transformers, hindering the provision of continuous and reliable data support for assessing the stress state of the transformer walls, early fault identification, and post-accident mechanism analysis. The industry urgently needs online pressure sensing methods that combine electromagnetic environment adaptability, insulation safety, oil resistance and durability, and wide range and high resolution.

[0020] The technical solutions provided by the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of a fiber Bragg grating pressure sensor according to the present invention. The present invention proposes an all-non-metallic fiber Bragg grating (FBG) pressure sensor for online monitoring of oil-immersed transformers, comprising: a housing, a secondary diaphragm, a main diaphragm, a variable lever mechanism, a force-bearing fiber Bragg grating, a reference fiber Bragg grating, and a top cover.

[0022] A pressure port is provided at one end of the outer casing, and the top cover is fixedly installed at the other end of the outer casing.

[0023] Inside the cavity of the outer casing, the secondary diaphragm is positioned close to the pressure port, while the primary diaphragm and secondary diaphragm are positioned at intervals.

[0024] The base of the variable lever mechanism is tightly pressed against the main diaphragm. One end of the force-bearing fiber grating is fixedly mounted on the output arm of the variable lever mechanism, and the other end is fixedly connected to the base of the variable lever mechanism, with the middle part suspended. The reference fiber grating is attached to the variable lever mechanism as a whole.

[0025] The cavity between the main diaphragm and the sub-diaphragm, as well as between the main diaphragm and the top cover, is filled with pressure-transmitting fluid at a preset pressure, so that the stressed fiber grating is taut when the sub-diaphragm is not subjected to external pressure.

[0026] In one or more embodiments of the present invention, specifically: Housing and Top Cover: The sensor body adopts a one-piece PEEK or ceramic housing and top cover structure. The housing has a pre-installed standard hydraulic interface, and the main seal is achieved through O-rings. The material has excellent dimensional stability and chemical resistance in oil immersion environments of -20–130 °C, and can resist the swelling of insulating oil and thermal aging for a long time. At the same time, the all-non-metallic design fundamentally avoids parasitic conductive paths and electromagnetic coupling problems.

[0027] The top cover has a retainer on the cavity side, and an optical fiber exit hole is opened on the side wall of the top cover. A buffer groove is provided between the retainer and the optical fiber exit hole. Both the stressed fiber grating and the reference fiber grating are led out to the retainer through optical fibers, and then guided through the buffer groove to the optical fiber exit hole for connection with the external demodulator. The optical fiber exit hole is equipped with a sealing cap / glue seal. The buffer groove is used to release the bending stress and thermal expansion and contraction displacement of the optical fiber, reduce the impact of assembly / temperature drift on zero point and repeatability, and provide optical fiber displacement margin and damping path under the impact load of external pressure to prevent the grating area from being stretched beyond the limit.

[0028] Sub-diaphragm: The sub-diaphragm uses Shore A 30–40 silicone rubber, prioritizing response to small pressure differentials to improve low-pressure resolution; its recommended geometry is 10–14 mm in diameter and 0.3–0.6 mm in thickness. With the variable lever and pressure-transmitting fluid, the equivalent lever ratio in the low-pressure range is approximately 1:3–1:6, corresponding to a typical sensitivity of 500 pm / MPa, used to capture small daily fluctuations and gradual trends. Overall nonlinearity <2.5–3%FS, hysteresis <1.5%FS, repeatability <1%FS.

[0029] Main diaphragm: The main diaphragm uses Shore A 60–70 silicone rubber, which gradually participates in load-bearing as the pressure increases to expand the measurement range and suppress saturation; its recommended size is 12–18 mm in diameter and 0.6–1.2 mm in thickness. Together with the auxiliary diaphragm, it can cover the entire measurement range of 0–15 MPa, and in the medium / high pressure range, the sensitivity is adjusted to 200 / 80 pm / MPa, ensuring an overload capacity ≥120%FS, and guaranteeing that it maintains structural and range margins under high-amplitude impacts.

[0030] The diameter and thickness windows of the primary and secondary diaphragms, together with their Shore hardness gradients, determine the segmented stiffness. If the secondary diaphragm is thinner and softer, it will cause the low pressure to deform first, thus improving the resolution. If the primary diaphragm is thicker and harder, the medium and high pressures will be gradually distributed, which can expand the measurement range and suppress saturation.

[0031] In this invention, the diameter and thickness windows of the main and auxiliary diaphragms, combined with their Shore hardness gradient and variable lever ratio, can cover an engineering range of 0~15 MPa, while ensuring nonlinearity / hysteresis / repeatability indicators, satisfying the requirements of low pressure high sensitivity + high pressure no overload.

[0032] Cavity and pressure-transmitting fluid: The cavity between the main and auxiliary diaphragms and the lever end cavity are filled with 100–1000 cSt silicone oil, and a micro-pre-charge of 0.02–0.05 MPa is applied during assembly to eliminate clearance and air bubbles, improving small-signal reversibility. This bulk elasticity and damping, combined with the diaphragm stiffness, ensure a smooth transition during segmented sensitivity switching and jointly support dynamic parameters of natural frequency ≥800–1000Hz and response time <1 ms.

[0033] The viscosity range of silicone oil is a trade-off between pressure transmission efficiency and damping / sealing stability. If the viscosity is too low, it will usually lead to leakage and difficulty in controlling bubbles, and increased zero-point drift in the low-pressure section; if the viscosity is too high, it will lead to slower high-frequency response and hysteresis due to volume elasticity when the temperature rises.

[0034] With a strength of 100–1000 cSt, it balances volumetric elasticity, damping, and sealing performance in an oil-immersed environment of -20–130 °C, supporting the entire system's natural frequency of 800–1000 Hz, response time of less than 1 ms, and long-term leakage rate. During assembly, a micro-pre-charge of 0.02–0.05 MPa is applied to eliminate clearance and air bubbles, significantly improving small-signal reversibility and repeatability.

[0035] Variable lever mechanism: The lever is made of POM / PEEK or carbon fiber composite material, with input / output arm lengths of 3–6 mm and 8–14 mm respectively, adjustable by hinges; the input end has a tapered contact surface, and the fulcrum is formed by a gradually changing elastic support that shifts inward with pressure. As the pressure increases, the contact radius expands and the fulcrum shifts inward, allowing the equivalent lever ratio to smoothly transition from 1:3–1:6 in the low-pressure range to 1:1–1:2 in the medium-high pressure range. This smoothly reduces the sensitivity from 500 pm / MPa to 200 pm / MPa and then to 80 pm / MPa, balancing small signal resolution and large impact unsaturation. This ensures that the entire unit achieves engineering specifications of nonlinearity <2.5–3%FS, hysteresis <1.5%FS, and repeatability <1%FS, facilitating high sensitivity response at small pressure differences and distributing load in the high-pressure range to prevent saturation.

[0036] In this invention, "input end" refers to the lever side (i.e., the side near the conical contact) that bears the hydraulic force from the diaphragm / pressure transmission fluid; in contrast, "output end" is the end at which micro-displacement / strain is applied to the force-bearing FBG.

[0037] The variable lever mechanism consists of three units: input arm, fulcrum, and output arm. The input arm is opposite to the conical contact member, the fulcrum is formed by an elastic support with gradually changing hardness (a variable fulcrum that moves inward with pressure), and the output arm is fixed at the end of the force FBG.

[0038] Force path: External pressure → secondary / primary diaphragm → pressure transmitting fluid → conical base (input arm) → variable fulcrum → micro-displacement of output arm → tensile force FBG generates Δλ. This achieves segmented characteristics of "high sensitivity at low pressure, moderate sensitivity at medium pressure, and anti-saturation at high pressure".

[0039] The base is designed with a tapered contact surface to allow the contact radius to expand adaptively as the pressure on the main diaphragm increases, thereby achieving a decrease in the equivalent lever ratio with pressure and segmented sensitivity; at the same time, it can avoid local stress concentration and early saturation; and it compensates for minor coaxiality errors through surface-to-line transition contact, maintaining repeatability and being tolerant to assembly.

[0040] Forced FBG and Reference FBG: Forced Fiber Bragg Grating λ sense With reference fiber grating λ ref Temperature field is consistent, λ sense Strain is applied by micro-displacement at the lever output end, λ ref Mechanical decoupling only senses temperature; demodulation terminals are paired with... Pressure conversion and secondary temperature compensation are implemented. The ultra-light weight and high rigidity assembly of the fiber optic link (50–150 µm adhesive layer, 10–50 µε pretension), combined with the above-mentioned geometry and leverage ratio settings, enable the sensor to maintain a dynamic bandwidth of 800–1000 Hz and a response time of <1 ms throughout the 0–15 MPa range.

[0041] The grid region of the stressed FBG is held in place by clamping / applying adhesive at the output arm end (adhesive layer 50–150 μm, pretension 10–50 µε). The reference FBG can be adhered to the body of the variable lever mechanism, that is, the reference FBG is decoupled from the mechanical link and is used only for temperature sensing.

[0042] Sealing and Interface: The main mating surfaces use fluororubber / FFKM O-rings, while secondary interfaces are sealed with redundant adhesive. Leakage rate is controlled to ≤10 Pa·m³ / s, ensuring long-term stability of the cavity volume and calibration curve, thus supporting the aforementioned nonlinear / hysteretic / repetitive performance targets and overload ≥120%FS. A standard hydraulic interface combined with a non-metallic isolation gasket ensures that the range and dynamic parameters are reproducible in tank wall / oil passage installation scenarios.

[0043] Based on this, the working principle of the present invention is as follows: Low-pressure operating mechanism: In the low-pressure operating range, the secondary diaphragm undergoes elastic deformation first, resulting in a smaller cone contact radius and a farther lever fulcrum position, thus forming a larger equivalent force arm ratio. At this time, the sensor exhibits high sensitivity and high resolution, effectively capturing daily fluctuations and gradual trends, providing a data basis for health assessment and threshold tuning.

[0044] Working mechanism of medium pressure section: When the pressure enters the medium pressure range, the main diaphragm begins to participate in load bearing, the equivalent stiffness of the cavity increases, the contact radius of the conical surface expands accordingly, and the fulcrum moves smoothly inward towards the input end. The equivalent force arm ratio decreases accordingly, and the sensitivity drops to a medium level, while maintaining good linearity and dynamic response, making it suitable for transient recording in the initial stage of short-circuit impact.

[0045] High-pressure section working mechanism: Under high-pressure impact scenarios, the main and auxiliary diaphragms work together to significantly improve the overall load-bearing stiffness, and the leverage ratio is further reduced to avoid sensor link saturation. This section balances wide measurement range and recoverability, enabling the sensor to record high-amplitude transient pressure peaks and rise-edge characteristics without distortion, which can be used for accident precursor identification and mechanism review.

[0046] Based on the fiber Bragg grating sensor of this invention, the measurement system can use an FBG demodulator with a sampling rate of ≥1 kHz and a resolution of ≤1 pm to synchronously acquire λ. sense With λ ref This ensures that both paths are triggered within the same clock domain. The combination of high sampling and high resolution not only guarantees the fidelity of transient peaks and rising edges, but also provides sufficient time-frequency information for subsequent denoising, event discrimination, and energy calculation.

[0047] Differential temperature compensation: First, the real-time differential wavelength is calculated to compensate for common temperature drift and light source fluctuations. Based on the temperature coefficient k obtained from calibration T The residual temperature drift was corrected a second time, and the corrected model is as follows: .

[0048] The superposition of the difference and coefficient methods can suppress zero-point drift and sensitivity drift with temperature during long-term operation over a wide temperature range, thus keeping the pressure estimation stable.

[0049] Pressure conversion: Input the temperature-compensated Δλ′ into the piecewise calibration function to obtain the pressure time series. The calibration function can be a piecewise linear or low-order polynomial with first-order continuity constraints between segments to ensure smooth, stepless, and hysteresis-free switching between different sensitivity segments.

[0050] Piecewise regression: During calibration, a single linear fit is used for the low-pressure segment, with a common zero-point constraint to ensure minimal zero drift; a single or double fit can be used for the medium-pressure segment to cover the nonlinearity of the gradual change in leverage ratio; a single fit is used for the high-pressure segment, and the pre-saturation margin is checked to be ≥10%FS. This strategy ensures simplicity while also considering fitting accuracy and traceability.

[0051] The fiber optic pressure sensor of this invention has a secondary diaphragm located close to the pressure interface within the cavity of the housing, and a primary diaphragm and secondary diaphragm spaced apart. The base of the variable lever mechanism is tightly abutted against the primary diaphragm. One end of the force-bearing fiber optic grating is fixedly mounted on the output arm of the variable lever mechanism, and the other end is fixedly connected to the base of the variable lever mechanism with the middle suspended. This forms a collaborative structure of "dual diaphragm - pressure-transmitting fluid - variable lever", which can achieve segmented adaptive sensitivity and wide range, avoiding the problems of insufficient small signal resolution and large impact saturation.

[0052] Specifically, a fiber optic grating (FBG) pressure sensor was designed, comprising a non-metallic housing and top cover, a dual-diaphragm-pressure-transmitting fluid pressure-bearing assembly, a variable lever transmission mechanism, a force-bearing FBG and a reference FBG, and an optical fiber holder and sealing component. Through the collaborative structure of "dual-diaphragm-pressure-transmitting fluid-variable lever", it achieves segmented adaptive characteristics of high sensitivity at low pressure, smooth transition at medium pressure, and anti-saturation at high pressure.

[0053] The system employs a non-metallic shell (PEEK / ceramic), non-metallic levers, and silicone oil pressure transmission fluid to completely eliminate parasitic conductive paths and eddy current coupling problems.

[0054] By using a micro-pre-charged hydraulic chamber, a lever structure, and a lightweight fiber optic link, the system achieves a natural frequency of 800-1000 Hz and a response time of <1 ms.

[0055] The use of a force-bearing FBG-reference FBG differential link combined with segmented calibration and secondary temperature coefficient correction effectively offsets temperature drift.

[0056] The proposed piecewise regression calibration method corresponds to the device geometry: the low-pressure section uses linear fitting with zero-point constraints, the medium-pressure section uses quadratic fitting to cover nonlinearity, and the high-pressure section uses linear fitting with a margin of ≥10% FS.

[0057] It should also be noted that the terms "comprising," "including," or any other variations thereof in this invention are intended to cover non-exclusive inclusion, that is, in addition to the elements listed in this invention, other elements not expressly listed may also be included.

[0058] The various embodiments in this invention are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0059] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A fiber Bragg grating pressure sensor, characterized in that, include: The outer casing, secondary diaphragm, main diaphragm, variable lever mechanism, force-bearing fiber optic grating, reference fiber optic grating, and top cover; A pressure port is provided at one end of the outer casing, and the top cover is fixedly installed at the other end of the outer casing; Inside the cavity of the outer casing, the secondary diaphragm is positioned close to the pressure port, while the primary diaphragm and the secondary diaphragm are positioned at intervals. The base of the variable lever mechanism and the main diaphragm are in elastic contact with each other. As the pressure on the main diaphragm increases, the contact area between the main diaphragm and the base of the variable lever mechanism increases, triggering the fulcrum migration of the variable lever mechanism. One end of the force-bearing fiber optic grating is fixedly mounted on the output arm of the variable lever mechanism, and the other end is fixedly connected to the base of the variable lever mechanism, with the middle part suspended in the air; the reference fiber optic grating is attached to the variable lever mechanism as a whole. The cavity between the main diaphragm and the sub-diaphragm, as well as between the main diaphragm and the top cover, is filled with pressure-transmitting fluid at a preset pressure, so that the stressed fiber grating is taut when the sub-diaphragm is not subjected to external pressure.

2. The fiber Bragg grating pressure sensor as described in claim 1, characterized in that, The base of the variable lever mechanism is a conical contact element, with its small end abutting against the main diaphragm.

3. The fiber Bragg grating pressure sensor as described in claim 1, characterized in that, The outer shell and top cover are made of PEEK or ceramic material, the variable lever mechanism is made of POM / PEEK or carbon fiber composite material, and the pressure transmission fluid is silicone oil.

4. The fiber Bragg grating pressure sensor as described in claim 1, characterized in that, The upper cover is provided with a retainer on the cavity side, and an optical fiber lead-out hole is opened on the side wall of the upper cover. A buffer groove is provided between the retainer and the optical fiber lead-out hole. Both the stressed fiber optic grating and the reference fiber optic grating are led out to the holder through optical fibers, and then guided through the buffer groove to the fiber optic exit hole for connection with the external demodulator. The fiber optic exit hole is equipped with a sealing cap / glue seal. The buffer groove is used to release the bending stress and thermal expansion and contraction displacement of the optical fiber, and to provide the optical fiber displacement margin and damping path under the impact load of external pressure.

5. The fiber Bragg grating pressure sensor as described in claim 1, characterized in that, The preset pressure is 0.02MPa~0.05MPa.

6. The fiber Bragg grating pressure sensor as described in claim 3, characterized in that, The viscosity of the silicone oil is 100 cSt to 1000 cSt.

7. The fiber Bragg grating pressure sensor as described in claim 1, characterized in that, The diameter of the sub-diaphragm is 10mm~14mm and the thickness is 0.3mm~0.6mm; The main diaphragm has a diameter of 12mm to 18mm and a thickness of 0.6mm to 1.2mm.

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