Fiber grating osmometer

Abstract

The application relates to the technical field of optical fiber sensing, in particular to an optical fiber grating osmotic pressure gauge which comprises a water permeable module, a sensing module, a packaging module and a signal transmission module; the sensing module comprises a diaphragm close to one end of the water permeable module, a movement core shell connected with the diaphragm, a movement core frame arranged in the movement core shell, a movement core, a pressure sensing optical fiber grating and a temperature sensing optical fiber grating; the movement core frame is fixedly connected with the diaphragm; the movement core comprises an elastic carrier for bearing the pressure sensing optical fiber grating, one end of the elastic carrier close to the diaphragm is connected with a first connecting piece, the first connecting piece is fixedly connected with the movement core frame, one end of the elastic carrier away from the diaphragm is connected with a second connecting piece, and one end of the second connecting piece close to the diaphragm is fixedly connected with the diaphragm; the pressure sensing optical fiber grating is located on the central axis of the movement core; when the diaphragm is pressed, the elastic carrier drives the pressure sensing optical fiber grating to produce tensile deformation along the movement core axis. The application solves the problem that the traditional optical fiber grating osmotic pressure gauge is prone to zero drift, and improves the precision and reliability of the product.

Description

A fiber optic grating piezometer Technical Field

[0001] This application relates to the technical field of fiber optic sensing, and in particular to a fiber Bragg grating piezometer. Background Technology

[0002] Fiber Bragg grating (FBG) sensor technology, which originated in the 1980s, offers advantages such as real-time monitoring, resistance to electromagnetic interference, and lightning strikes. With technological advancements, its measurement accuracy and reliability have continuously improved, and its application areas have expanded. FBG piezometers, as a derivative product of this technology, are widely used in fields such as hydraulic engineering and geotechnical engineering.

[0003] Currently, traditional fiber optic grating piezometers have certain problems during operation. For example, Chinese patent (patent number: ZL201020655834.3) discloses a grating water pressure sensor, including a sleeved grating protective tube and an outer cylinder, a permeable seat embedded in the front end of the outer cylinder, a permeable stone embedded inside the permeable seat, a mechanism seat connected to the front end of the grating protective tube and the inner wall of the outer cylinder, a diaphragm disposed at the front end of the mechanism seat, a rear plug inserted into the rear end of the grating protective tube and the outer cylinder, an armored connector inserted into the rear plug, and an armored optical cable inserted into the armored connector. A strain gauge is connected between the diaphragm and the mechanism seat, and a grating is attached to the strain gauge. The grating is connected to the armored optical cable via an optical fiber.

[0004] The working principle of this grating water pressure sensor is as follows: Water permeates through the permeable stone into the cavity formed by the permeable seat, outer cylinder, and sensor core. The water pressure outside the permeable stone gradually increases, causing the water pressure inside the cavity to increase. This water pressure squeezes the diaphragm, causing it to deflect inwards. This causes the moving end of the strain gauge attached to the diaphragm to change, resulting in compression deformation of the strain gauge. This causes a wavelength change in the grating attached to the strain gauge, which is then transmitted through an optical fiber. The signal is demodulated by a demodulator to obtain the pressure change value.

[0005] However, when the fiber optic water pressure sensor is left unattended for a long time, the fiber optic grating is prone to zero drift, and vibrations during transportation can easily cause the fiber optic grating to break, resulting in the failure of the fiber optic grating piezometer.

[0006] Therefore, developing a fiber optic grating piezometer that is less prone to zero drift and damage has become an important issue that urgently needs to be addressed. Summary of the Invention

[0007] To address the technical problem of easy zero drift of the internal grating in existing fiber Bragg grating piezometers, this application provides a fiber Bragg grating piezometer.

[0008] A fiber Bragg grating piezometer includes a water permeability module, a sensing module, an encapsulation module, and a signal transmission module. The water permeability module transmits the water pressure from the external environment to the sensing module. The sensing module is disposed within the encapsulation module and is used to sense the water pressure and convert it into an optical signal. The signal transmission module is connected to the sensing module and is used to transmit the optical signal to an external adjustment device.

[0009] The sensing module includes a diaphragm near one end of the water-permeable module, a core housing fixedly connected to the diaphragm, and a core frame, core, pressure-sensitive fiber optic grating, and temperature-sensitive fiber optic grating disposed within the core housing.

[0010] The core frame is located on the side of the membrane away from the water-permeable module, and the membrane is fixedly connected to the core frame;

[0011] The core includes an elastic carrier for carrying a pressure-sensitive fiber Bragg grating. A first connector is connected to one end of the elastic carrier near the diaphragm, and the first connector is fixedly connected to the core frame. A second connector is connected to one end of the elastic carrier away from the diaphragm, and the end of the second connector near the diaphragm is fixedly connected to the diaphragm.

[0012] The pressure-sensitive fiber grating is located on the central axis of the core, and when the diaphragm is compressed, the elastic carrier drives the pressure-sensitive fiber grating to undergo tensile deformation along the core axis.

[0013] The mechanism also includes a support for carrying a temperature-sensitive fiber Bragg grating, which is located on the central axis of the mechanism and connected to the pressure-sensitive fiber Bragg grating.

[0014] According to the inventor's analysis, the reason why the fiber optic water pressure sensor disclosed in the aforementioned patent 201020655834.3 is prone to zero drift is that the fiber optic grating converts the compression deformation of the fiber optic grating into an optical signal. In order to adapt to the compression deformation of the fiber optic grating, the fiber optic grating is initially under a state of extreme pretension. However, as time goes on, due to problems such as stress relaxation or creep of the core material, the pretension acting on the fiber optic grating decreases, and the fiber optic grating exhibits compressive strain under no pressure, thus causing zero drift.

[0015] In the fiber Bragg grating piezometer of this application, the first connector of the core is fixed to the core frame. When the diaphragm is subjected to water pressure from the permeable module, the diaphragm is compressed and the deformation is transmitted to the far end of the core through the second connector. The pressure on the core is converted into tensile stress on the core. As the pressure increases, the elongation of the pressure-sensitive fiber Bragg grating increases. Therefore, this invention enables the pressure-sensitive fiber Bragg grating to be in a state of extremely low tensile stress in the initial state. The elongation of the pressure-sensitive fiber Bragg grating only gradually increases after loading. This effectively solves the technical problem of zero drift that existing fiber Bragg grating piezometers are prone to. It not only improves the reliability of the fiber Bragg grating, but also reduces the risk of damage to the internal structure of the piezometer, and further improves the measurement accuracy of the pressure-sensitive fiber Bragg grating piezometer.

[0016] In addition, the mechanism includes an elastic carrier for supporting the pressure-sensitive fiber Bragg grating and a carrier for supporting the temperature-sensitive fiber Bragg grating. On the one hand, the mechanism protects the pressure-sensitive and temperature-sensitive fiber Bragg gratings, improving their reliability within the piezometer. On the other hand, the elastic carrier causes the pressure-sensitive fiber Bragg grating to undergo tensile deformation along the axial direction of the mechanism. The temperature-sensitive fiber Bragg grating is connected to the pressure-sensitive fiber Bragg grating, further reducing the influence of temperature on pressure measurement and improving the measurement accuracy of the fiber Bragg grating piezometer.

[0017] Furthermore, the pressure-sensitive fiber grating and the temperature-sensitive fiber grating are fixed to the central axis of the mechanism by welding.

[0018] Through the above technical solution, the fiber Bragg grating is fixed by high-temperature welding instead of traditional adhesive fixing, which further reduces the risk of creep or detachment of the fiber Bragg grating after long-term use, effectively improves the reliability of the fiber Bragg grating, solves the problem of poor consistency of mass-produced products, and further improves the measurement accuracy of the fiber Bragg grating piezometer.

[0019] Furthermore, the elastic carrier includes a deformation component, which comprises two deformable elements symmetrically arranged along the axial direction of the pressure-sensitive fiber grating.

[0020] Through the above technical solution, since the deformable parts are symmetrically distributed along the axis of the pressure-sensitive fiber Bragg grating, after the deformable parts are subjected to tensile force, their deformation acts on both sides of the pressure-sensitive fiber Bragg grating, realizing the axial strain of the pressure-sensitive fiber Bragg grating. This ensures that the force on the pressure-sensitive fiber Bragg grating is evenly distributed. Furthermore, the symmetrical deformation of the deformable parts can avoid local twisting of the pressure-sensitive fiber Bragg grating, ensuring that the pressure-sensitive fiber Bragg grating can deform along the axis, so that the pressure-sensitive fiber Bragg grating can be subjected to uniform force. This facilitates the pressure-sensitive fiber Bragg grating to return to its initial state after the pressure is removed, further preventing the zero drift problem of the fiber Bragg grating and improving the measurement accuracy of the fiber Bragg grating piezometer.

[0021] Furthermore, the deformable component includes a connecting portion and movable portions disposed at both ends of the connecting portion, wherein the movable portions at both ends extend and contract along the axial direction of the pressure-sensitive fiber grating.

[0022] Through the above technical solutions, the free expansion and contraction design of the movable part can further amplify small deformations and further improve the response capability of the fiber Bragg grating to small pressure changes, thereby improving the sensitivity and measurement accuracy of the fiber Bragg grating piezometer.

[0023] Furthermore, at least two sets of the deformation components are provided, and multiple deformation elements are distributed sequentially along the axial direction of the pressure-sensitive fiber grating, with adjacent deformation elements connected sequentially.

[0024] Through the above technical solution, multiple sets of deformation components are set, which are suitable for large-scale pressure monitoring. The sequential distribution of multiple adjacent deformation components makes the tensile deformation of the elastic carrier more uniform, thereby enabling the strain to be uniformly transmitted along the axial direction of the pressure-sensitive fiber grating. On the other hand, the expansion and contraction deformation of the movable parts at both ends of a single deformation component is smaller, and it is more flexible in returning to its original shape. Therefore, the pressure-sensitive fiber grating can also recover freely and will not be in a stretched state for a long time, further reducing the occurrence of zero drift in the pressure-sensitive fiber grating and improving the measurement accuracy of the fiber grating.

[0025] Furthermore, the movement frame includes a first mounting base and a second mounting base. The first mounting base is fixedly connected to the movement through the first connector and is tightly coupled to the inner side of the movement housing. The second mounting base is fixedly connected to the diaphragm.

[0026] Through the above technical solution, the installation stability of the frame is improved by setting the first mounting base and the second mounting base, preventing the frame from shaking and affecting the measurement accuracy of the optical efficiency grating, thus improving the reliability of the fiber grating. Furthermore, since the pressure-sensitive fiber grating is set on the central axis of the frame, the stability of the frame can further stabilize the pressure-sensitive fiber grating on the frame, thereby further reducing the occurrence of zero drift in the pressure-sensitive fiber grating.

[0027] Furthermore, the permeable module includes a permeable base and a permeable stone, with the permeable stone installed on the permeable base.

[0028] Through the above technical solutions, permeable stones can intercept sediment particles, guide water flow to quickly infiltrate and maintain pressure transmission efficiency, making them suitable for underwater environments. Furthermore, permeable stones can be independently disassembled for cleaning or replacement, thus improving the lifespan of permeable modules.

[0029] Furthermore, the encapsulation module includes a piezometer outer cylinder and a piezometer rear plug. The sensing modules are all disposed inside the piezometer outer cylinder. One end of the piezometer outer cylinder is fixedly connected to the permeable module, and the other end is fixedly connected to the piezometer rear plug.

[0030] Through the above technical solution, the outer side of the sensor module's core housing is tightly connected to the inner side of the piezometer's outer cylinder. The water-permeable module is set at one end of the piezometer to transmit the water pressure from the external environment to the sensor module, while the other end is sealed by the piezometer's rear plug to prevent liquid intrusion from affecting the measurement accuracy of the fiber Bragg grating and improve the sealing performance of the fiber Bragg grating piezometer.

[0031] Furthermore, the signal transmission module includes an armored connector, an armored optical cable, and a stainless steel sleeve. The armored connector is mounted on the piezometer's rear plug, and the armored optical cable is connected to the armored connector via the stainless steel sleeve.

[0032] Through the above technical solution, the armored optical cable is connected to the armored connector through a stainless steel sleeve, which can further enhance the stability of the connection between the armored connector and the armored optical cable and reduce the damage of external forces to the signal transmission module.

[0033] Furthermore, a thicker tail sleeve is also fitted over the stainless steel sleeve.

[0034] Through the above technical solution, the thick tail sleeve provides additional mechanical protection for the armored optical cable, and the external thick tail sleeve can reduce the entry of external moisture into the fiber Bragg grating piezometer, thus improving the product's sealing performance.

[0035] In summary, this application has at least the following beneficial effects:

[0036] 1. The fiber Bragg grating piezometer of this application enables the fiber Bragg grating to be in an extremely low tensile stress state in the initial state, and the elongation of the fiber Bragg grating only gradually increases after loading. This effectively solves the technical problem that existing fiber Bragg grating piezometers are prone to zero drift due to being in a high tension state for a long time. This not only improves the reliability of the fiber Bragg grating and reduces the risk of damage to the internal structure of the piezometer, but also further improves the measurement accuracy of the fiber Bragg grating piezometer.

[0037] 2. The fiber grating fixing method of the fiber grating piezometer of this application adopts high-temperature welding instead of traditional adhesive fixing, which further reduces the risk of creep or detachment of the fiber grating after long-term use, effectively improves the reliability of the fiber grating, solves the problem of poor consistency of mass-produced products, and further improves the measurement accuracy of the fiber grating piezometer.

[0038] 3. The fiber Bragg grating piezometer of this application has a deformable component on its elastic carrier. The deformable component is symmetrically distributed along the axis of the pressure-sensitive fiber Bragg grating. When the deformable component is subjected to tensile force, its deformation acts on both sides of the pressure-sensitive fiber Bragg grating, realizing the axial strain of the pressure-sensitive fiber Bragg grating. This ensures that the force on the pressure-sensitive fiber Bragg grating is evenly distributed. Furthermore, the symmetrical deformation of the deformable component can avoid the local twisting of the pressure-sensitive fiber Bragg grating, effectively improving the measurement accuracy of the fiber Bragg grating piezometer. Attached Figure Description

[0039] Figure 1 is a schematic diagram of the right view of a fiber optic grating piezometer provided in an embodiment of the present invention, with AA cross-section.

[0040] Figure 2 is an AA cross-sectional view of a fiber optic grating piezometer provided in an embodiment of the present invention;

[0041] Figure 3 is a schematic diagram of the BB cross-section of a right view of a fiber optic grating piezometer provided in an embodiment of the present invention;

[0042] Figure 4 is a cross-sectional view of the BB of a fiber Bragg grating piezometer provided in an embodiment of the present invention;

[0043] Figure 5 is a partial structural schematic diagram of a fiber optic grating piezometer provided in an embodiment of the present invention;

[0044] Figure 6 is a partial structural enlarged view of a fiber optic grating piezometer provided in an embodiment of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1. Permeable module; 11. Permeable base; 12. Permeable stone;

[0047] 2. Sensing module; 21. Diaphragm; 22. Mechanism housing; 23. Mechanism frame; 24. Mechanism; 25. Fiber Bragg grating; 221. Mechanism outer cylinder; 222. Mechanism rear plug; 231. First mounting base; 232. Second mounting base; 241. Elastic carrier; 242. Bearing base; 243. First connector; 244. Second connector; 245. First weld joint; 246. Second weld joint; 247. Third weld joint; 251. Pressure-sensitive fiber Bragg grating; 252. Temperature-sensitive fiber Bragg grating; 2411. Deformable part; 2431. First screw; 2441. Second screw; 24111. Connecting part; 24112. First movable part; 24113. Second movable part.

[0048] 3. Packaging module; 31. Piezometer outer cylinder; 32. Piezometer rear plug;

[0049] 4. Signal transmission module; 41. Armored connector; 42. Armored optical cable; 43. Stainless steel sleeve; 44. Thick tail sleeve. Detailed Implementation

[0050] The present application will be further described below with reference to Figures 1-6.

[0051] Referring to Figures 1-2, the present invention provides a fiber optic grating piezometer, including a water permeability module 1, a sensing module 2, an encapsulation module 3, and a signal transmission module 4. The water permeability module 1 transmits the water pressure from the external environment to the sensing module 2. The sensing module 2 is disposed in the encapsulation module 3 and is used to sense the water pressure and convert it into an optical signal. The signal transmission module 4 is connected to the sensing module 2 and is used to transmit the optical signal to an external device.

[0052] The permeable module 1 includes a permeable base 11 and a permeable stone 12, with the permeable stone 12 embedded in the front end of the permeable base 11. The sensing module 2 includes a diaphragm 21 near the end of the permeable base 11, a core housing 22 fixedly connected to the diaphragm 21, and a core frame 23, a core 24, and a fiber optic grating 25 disposed within the core housing 22. The core frame 23 is located on the side of the diaphragm 21 away from the permeable base 11 and is fixedly connected to the diaphragm 21. The core 24 is fixed on the core frame 23, with the end of the core 24 near the diaphragm 21 fixed to the diaphragm 21. The fiber optic grating 25 is fixed on the core 24. The core housing 22 includes a core outer cylinder 221 and a core rear plug 222. One end of the core outer cylinder 221 is connected to the diaphragm 21, and the end away from the diaphragm 21 is connected to the core rear plug 222.

[0053] Specifically, in this embodiment, the diaphragm 21 is a cover-shaped structure, the movement frame 23 is fixed to the diaphragm 21 by a threaded connection, and the diaphragm 21 is fixed to the movement rear plug 222 by welding to the movement outer cylinder 221.

[0054] Referring to Figures 3-5, the fiber Bragg grating 25 includes a pressure-sensitive fiber Bragg grating 251 and a temperature-sensitive fiber Bragg grating 252, which are connected and located on the central axis of the core 24. The core 24 includes an elastic carrier 241 for supporting the pressure-sensitive fiber Bragg grating 251 and a support seat 242 for supporting the temperature-sensitive fiber Bragg grating 252. The end of the elastic carrier 241 near the diaphragm 21 is connected to a first connector 243, which is fixedly connected to the first mounting seat 231 of the core frame 23 via a first screw 2431. The end of the elastic carrier 241 away from the diaphragm 21 is provided with a second connector 244, which is fixedly connected to the diaphragm 21 via a second screw 2441 passing through the second mounting seat 232 of the core frame 23. When the diaphragm 21 is compressed, the core 24 is subjected to the pressure of the diaphragm 21, forming a tensile force at the distal end of the core 24. The elastic carrier 241 drives the pressure-sensitive fiber grating 251 to undergo tensile deformation along the axial direction of the core 24.

[0055] Specifically, in this embodiment, the first mounting base 231 of the movement frame 23 is tightly connected to the inner side of the movement housing 22, further improving the installation stability of the movement frame.

[0056] Referring to Figure 6, the elastic carrier 241 includes a deformation component, which includes two deformable parts 2411 symmetrically arranged along the axis of the pressure-sensitive fiber grating 251. Each deformable part includes a connecting portion 24111 and a first movable portion 24112 and a second movable portion 24113 disposed on both sides of the connecting portion. The first movable portion 24112 and the second movable portion 24113 are stretched and deformed along the axial direction of the pressure-sensitive fiber grating, and the distance between the first movable portion 24112 and the second movable portion 24113 increases as the pressure-sensitive fiber grating 251 is stretched, and returns to the initial distance as the pressure-sensitive fiber grating is reset.

[0057] In this embodiment, two sets of deformation components are provided, with two adjacent deformation components 2411 connected in sequence and distributed sequentially along the axial direction of the pressure-sensitive fiber optic grating 251.

[0058] Specifically, the elastic carrier uses titanium alloy as the main material, which further improves the rigidity of the fiber Bragg grating piezometer and also improves the corrosion resistance of the internal components of the piezometer.

[0059] Referring to Figure 5, the pressure-sensitive fiber grating 251 and the temperature-sensitive fiber grating 252 are fixed to the central axis of the mechanism 24 by welding. The mechanism 24 is provided with a first welding port 245, a second welding port 246 and a third welding port 247. The pressure-sensitive fiber grating 251 is located between the first welding port 245 and the second welding port 246, and the temperature-sensitive fiber grating 252 is located between the second welding port 246 and the third welding port 247.

[0060] Referring to Figure 2, the encapsulation module 3 includes a piezometer outer cylinder 31. One end of the piezometer outer cylinder 31 is fixedly connected to the permeable seat 11, and the other end is provided with a piezometer rear plug 32. The sensing module 2 is disposed inside the piezometer outer cylinder 31, and the outer side of its mechanism housing 22 is tightly connected to the inner side of the piezometer outer cylinder 31. The signal transmission module 4 includes an armored connector 41, an armored optical cable 42, a stainless steel sleeve 43, and a thick tail sleeve 44. The armored connector 41 is disposed on the piezometer rear plug 32. The armored optical cable 42 is connected to the armored connector 41 through the stainless steel sleeve 43. The thick tail sleeve 44 is fitted on the outer side of the stainless steel sleeve 43. The optical fiber of the fiber optic grating 25 inside the sensing module 2 is connected to the armored optical cable 42 in sequence through the mechanism rear plug 222 and the piezometer rear plug 32.

[0061] The working principle of this invention is as follows: As shown in Figure 2, water permeates through the permeable stone 12 into the cavity formed by the permeable seat 11, the outer cylinder 31 of the piezometer, and the sensing module 2. The water pressure outside the permeable stone 12 gradually increases, causing the water pressure inside the cavity to increase. The diaphragm 21 is subjected to water pressure, which drives the distal end of the core 24 connected to the diaphragm 21 to generate a tensile force, thereby causing the elastic carrier 241 inside the core 24 to undergo tensile deformation, causing the pressure-sensitive fiber optic grating 251 welded on the core 24 to change wavelength. The optical signal is then transmitted through the optical fiber and demodulated by the demodulator to obtain the pressure change value.

[0062] The above are preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A fiber optic grating piezometer, characterized in that: The device includes a water-permeable module, a sensing module, an encapsulation module, and a signal transmission module. The water-permeable module transmits the water pressure from the external environment to the sensing module. The sensing module, housed within the encapsulation module, senses the water pressure and converts it into an optical signal. The signal transmission module, connected to the sensing module, transmits the optical signal to an external regulating device. The sensing module includes a diaphragm near one end of the water-permeable module, a core housing fixedly connected to the diaphragm, and a core frame, a core, a pressure-sensitive fiber Bragg grating, and a temperature-sensitive fiber Bragg grating housed within the core housing. The core frame is located on the side of the diaphragm facing away from the water-permeable module, and the diaphragm is fixedly connected to the core frame. The core includes an elastic carrier for supporting the pressure-sensitive fiber Bragg grating, and the elastic carrier includes a deformation component. The deformation assembly includes two deformable members symmetrically arranged along the axial direction of the pressure-sensitive fiber Bragg grating. A first connector is connected to the end of the elastic carrier near the diaphragm, and the first connector is fixedly connected to the core frame. A second connector is connected to the end of the elastic carrier away from the diaphragm, and the end of the second connector near the diaphragm is fixedly connected to the diaphragm. The pressure-sensitive fiber Bragg grating is located on the central axis of the core frame, and when the diaphragm is compressed, the elastic carrier causes the pressure-sensitive fiber Bragg grating to undergo tensile deformation along the axial direction of the core frame. The core frame also includes a support for a temperature-sensitive fiber Bragg grating, which is located on the central axis of the core frame and connected to the pressure-sensitive fiber Bragg grating. The pressure-sensitive fiber Bragg grating and the temperature-sensitive fiber Bragg grating are fixed to the central axis of the core frame by welding.

2. The fiber optic grating piezometer according to claim 1, characterized in that: The deformable component includes a connecting part and movable parts disposed at both ends of the connecting part, and the movable parts at both ends extend and contract along the axial direction of the pressure-sensitive fiber grating.

3. The fiber optic grating piezometer according to claim 2, characterized in that: The deformation components are provided in at least two groups, and multiple deformation elements are distributed sequentially along the axial direction of the pressure-sensitive fiber grating, with adjacent deformation elements connected sequentially.

4. The fiber optic grating piezometer according to claim 1, characterized in that: The movement frame includes a first mounting base and a second mounting base. The first mounting base is fixedly connected to the movement through the first connector and is tightly coupled to the inner side of the movement housing. The second mounting base is fixedly connected to the diaphragm.

5. A fiber optic grating piezometer according to claim 1, characterized in that: The permeable module includes a permeable base and permeable stones, with the permeable stones installed on the permeable base.

6. A fiber optic grating piezometer according to claim 1, characterized in that: The encapsulation module includes a piezometer outer cylinder and a piezometer rear plug. The sensing modules are all installed inside the piezometer outer cylinder. One end of the piezometer outer cylinder is fixedly connected to the water-permeable module, and the other end is fixedly connected to the piezometer rear plug.

7. A fiber optic grating piezometer according to claim 6, characterized in that: The signal transmission module includes an armored connector, an armored optical cable, and a stainless steel sleeve. The armored connector is mounted on the rear plug of the piezometer, and the armored optical cable is connected to the armored connector through the stainless steel sleeve.

8. A fiber optic grating piezometer according to claim 7, characterized in that: A thicker tail sleeve is also fitted over the stainless steel sleeve.

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