A Liquid Metal Fiber Bragg Grating Sensor

Abstract

The present invention provides a liquid metal fiber grating sensor, comprising an inner layer of liquid metal optical fiber, which adopts a layering process to naturally combine the atomization of liquid metal and the deposition of atomized molten droplets, and densely adheres the liquid metal to the fiber core as a whole; a plastic spraying process is adopted on the liquid metal cladding, and plastic powder is charged by a high-voltage electrostatic device, and the powder is uniformly adsorbed to form a powdery coating, and the PVC coating layer is very dense and effectively isolates water and other harmful substances; the protective main board and the protective sub-board are both arranged in an arc shape, so that six protective main boards and six protective sub-boards are moved to form a lantern shape, and support the inner layer of the airbag, so that after the outer shell is deformed by pressure, it is supported by the protective main board and the protective sub-board, thereby improving the pressure-bearing capacity of the outer shell, thereby improving the protection performance of the optical fiber, and improving the service life of the optical fiber.

Description

Technical Field

[0001] The present invention relates to the field of measurement technology not dedicated to specific variables, and in particular to a liquid metal fiber grating sensor. Background Art

[0002] Fiber Bragg grating is a grating located inside an optical fiber. It is a diffraction grating formed by periodically modulating the refractive index of the fiber core axially through laser writing. Because its resonant wavelength is sensitive to changes in external environments such as temperature, strain, refractive index, and concentration, it has been widely used in the field of fiber optic sensing. In actual applications, fiber Bragg grating sensors are constrained by various structural environments and have a low survival rate and are severely damaged. The main reason is that the strength of the sensitive component optical fiber is not enough and it is prone to brittle fracture. Protecting the sensor mainly involves encapsulating the main part of the sensor and strengthening the internal optical fiber material, thereby achieving the invention purpose of protecting the fiber Bragg grating sensor and thereby increasing the service life of the sensor.

[0003] Research on protecting fiber grating sensors has found the following problems:

[0004] Existing fiber optic sensors still have defects in accuracy and range and potential safety hazards in use: 1. The shape and material of the optical fiber are prone to breakage and lack flexibility; 2. The strain to be measured in geotechnical engineering is large, and there are factors such as groundwater, and the mechanical and corrosion resistance of the optical fiber will cause hidden dangers; 3. The existing fiber gratings are not clear and have a small range, requiring multiple sections of fusion connection, the measurement range is incomplete, and there is a gap in measurement accuracy. Therefore, it is necessary to improve the material itself and improve the production process.

[0005] Fiber Bragg gratings are easily damaged, which will greatly reduce the service life of the sensor. The existing protective sensors are protected by the outer shell, and the outer shell is deformed by external forces during the protection of the sensor, causing the outer shell to be damaged. After the outer shell is damaged, the protection strength of the fiber Bragg grating is reduced or even disappears. Therefore, it is necessary to improve the protective shell structure and insert reinforcement materials.

[0006] At present, CN116625264A in the prior art is a liquid metal fiber Bragg grating strain sensor, which discloses a liquid metal optical fiber and a sensor housing. The invention uses a fiber Bragg grating sensor as the main part, and the liquid metal optical fiber with a grating is directly inserted. Not only does the liquid metal cladding and the PVC coating layer jointly protect and isolate the optical fiber, but the outer layer of the liquid metal fiber Bragg grating can also be wrapped with buffer and reinforcement materials, such as nylon fiber, Kevlar fiber, etc. The interior of the main body can be air, or filled with nitrogen or inert gas to protect the optical fiber, or can be liquid such as heat transfer oil, etc.

[0007] The present invention can mainly solve the problem that the fiber Bragg grating itself is easily damaged in groundwater or complex construction environment, resulting in damage to mechanical properties and service life, and the shell cannot protect the fiber Bragg grating during the sensor protection process, resulting in the shell failing to increase the service life of the sensor. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a liquid metal fiber grating sensor to solve the problems described in the above background technology.

[0009] The purpose and efficacy of a liquid metal fiber grating sensor of the present invention are achieved by the following specific technical means: a liquid metal fiber grating sensor, including an inner layer of liquid metal optical fiber, adopts a layering process to naturally combine the atomization of liquid metal and the deposition of atomized droplets, and the liquid metal is densely attached to the fiber core as a whole. A plastic spraying process is adopted on the liquid metal cladding, and the plastic powder is charged by a high-voltage electrostatic device, and the powder is uniformly adsorbed to form a powdery coating. The PVC coating layer is very dense and effectively isolates water and other harmful substances; it includes a shell, one end of the shell is equipped with a sealing end, and a side of the sealing end away from the shell is equipped with an optical fiber connector, the inside of the shell is equipped with an optical fiber, and the inner wall of the shell is provided with a driving induction component, the induction component includes an airbag, a sleeve block, a connecting block and a reset spring, the inner side of the airbag is provided with a sleeve block, one side of the sleeve block is provided with a connecting block, and the inside of the sleeve block is provided with a reset spring.

[0010] Furthermore, the liquid metal grating sensor adopts a femtosecond direct writing process to engrave the grating, without the need to strip the optical fiber coating, and the manufacturing process is simpler. The femtosecond laser is controlled by an electrically controlled shutter, and the grating is engraved point by point through light attenuation control and polarization control. Through the precise movement of the translation stage, it can directly penetrate the PVC coating, and a uniform grating with a constant period is engraved on the surface of the fiber core.

[0011] Furthermore, the airbag is filled inside the shell, and the airbag is arranged in a two-layer wrapping shape. The outer layer of the airbag is provided with a protective component for support, and the inner layer of the airbag is provided with two through holes, and the inner layer of the airbag is in contact with the sleeve block.

[0012] Furthermore, the interior of the sleeve block is hollow, and the size of the openings at its left and right ends matches the connecting block. The sleeve block is arranged in an arc shape, and there are three of them, and every two adjacent sleeve blocks are connected by a connecting block.

[0013] Furthermore, the three sleeve blocks are connected with the three connection blocks to form a circular ring, and the circular ring is nested in the outer side surface of the optical fiber without being fitted.

[0014] Furthermore, the connection block is arranged in an arc shape, the curvature of the outer side surface of the connection block matches the curvature of the inner wall of the sleeve block, and every two adjacent connection blocks among the three connection blocks are connected by a reset spring.

[0015] Furthermore, the protective assembly includes a protective main board, a protective sub-board, a push block, a push rod, a first fixed block, a connecting rod and a second fixed block. The first fixed block is installed on the outer side of the protective main board, the connecting rod is installed on the bottom of the first fixed block, the protective sub-board is provided on the outer side of the connecting rod, the second fixed block is installed on the end of the connecting rod away from the first fixed block, the push block is installed on the bottom of the second fixed block, and the push block is installed on the end of the push rod away from the second fixed block.

[0016] Furthermore, the protective main boards are arranged in an arc shape and are provided in six numbers, and through holes are opened at the edges of both ends of the four middle protective main boards, and the diameter of the through holes matches the diameter of the connecting rod; one of the two outermost protective main boards has a through hole opened at the edge of one top end, and the other has a through hole opened at the edge of the bottom; and every two adjacent protective main boards among the six protective main boards are connected by a protective sub-board.

[0017] Furthermore, the protective sub-plates are arranged in an arc shape and at an angle, and every two protective main plates are connected to a protective sub-plate in an "N" shape. There are six protective sub-plates, and the two end edges of the middle four protective sub-plates are provided with through holes matching the connecting rods. The two outermost protective sub-plates have one through hole at the top end edge and the other at the bottom edge.

[0018] Furthermore, one end of the push block away from the push rod is connected to the outer side surface of the adjacent sleeve block.

[0019] Furthermore, two push rods are provided, one end of the upper push rod away from the push block is connected to the bottom of the middle right protective sub-plate, and one end of the lower push rod away from the push block is connected to the top of the middle left protective sub-plate.

[0020] Beneficial effects:

[0021] 1. Liquid metal optical fiber has good toughness, and has the characteristics of light guiding, heat insulation, and corrosion resistance. The grating sensor has clear gratings, and the grating writing length covers a large area, avoiding the fragility of the fusion point caused by multiple melting sections. The manufacturing process of liquid metal optical fiber is simple and the process precision is high. The advantages of liquid metal fiber grating sensors are: combining data transmission and information sensing together, with low data loss and long distance; simple layout, long wiring, low cost, and easy engineering application; the acquisition frequency can reach the sub-second level, which has advantages in real-time monitoring and cost.

[0022] 2. When the outer shell surface is deformed by external force, the pressure on the outer shell surface drives the airbag to be compressed. When any point on the airbag surface is subjected to external force and the pressure increases, it can be instantly transmitted to the filling gas to cause flow and resistance. Therefore, when the outer layer of the airbag is compressed, the outer layer squeezes the inner layer, and the inner layer wraps the sleeve and squeezes the sleeve. The sleeve shrinks inward due to the squeezing, so that the sleeve accommodates the connecting block. The diameter of the ring formed by the compressed sleeve and the connecting block is reduced, and it does not fit the optical fiber, thereby preventing the outer shell from being damaged due to pressure;

[0023] 3. The diameter of the ring formed by the sleeve block and the connecting block is reduced, so that the sleeve block moves. After the two sleeve blocks close to the protective sub-plate move, they drive the two push blocks to move. The two push blocks pull the two middle protective main plates and the protective sub-plates through the push rods to move. After the protective sub-plate moves, every two protective main plates are connected to one protective sub-plate in an "N" shape, so that the protective sub-plate forms an "X" shape with the protective main plate after moving;

[0024] 4. After the protective sub-plate is tilted, it pushes the protective main plate at one end, and the six protective sub-plates drive the six protective main plates to move. The protective main plates and the protective sub-plates are both arranged in an arc shape, so that the six protective main plates and the six protective sub-plates form a lantern shape after moving, and support the inner layer of the airbag, so that after the outer shell is deformed by pressure, it is supported by the protective main plate and the protective sub-plate, thereby improving the pressure-bearing capacity of the outer shell, thereby improving the protection performance of the optical fiber, and increasing the service life of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 It is a schematic diagram of the cross-sectional structure of the airbag of the present invention;

[0027] Figure 3 It is a schematic diagram of the airbag structure of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of the protection component of the present invention;

[0029] Figure 5 This is a schematic diagram of the push block connection structure of the present invention;

[0030] Figure 6 This is a schematic diagram of the block structure of the present invention;

[0031] Figure 7 It is a schematic diagram of the connection structure of the connection block of the present invention.

[0032] Figure 1-7 In the figure, the corresponding relationship between the component names and the figure numbers is as follows:

[0033] 1. Shell; 101. Optical fiber; 102. Optical fiber connector; 103. Sealing end; 2. Airbag; 201. Bushing block; 202. Connecting block; 203. Reset spring; 3. Protective main board; 301. Protective sub-board; 302. Push block; 303. Push rod; 304. First fixed block; 305. Connecting rod; 306. Second fixed block. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] As attached Figure 1 To Attachment Figure 7 As shown: Example

[0036] A liquid metal fiber Bragg grating sensor comprises a housing 1, a sealing end 103 is installed at one end of the housing 1, a fiber connector 102 is installed on the side of the sealing end 103 away from the housing 1, an optical fiber 101 is installed inside the housing 1, and a driving sensing component is arranged on the inner wall of the housing 1, the sensing component comprises an airbag 2, a sleeve block 201, a connecting block 202 and a reset spring 203;

[0037] A sleeve block 201 is disposed on the inner side of the airbag 2, a connecting block 202 is disposed on one side of the sleeve block 201, and a return spring 203 is disposed inside the sleeve block 201;

[0038] The airbag 2 is filled inside the shell 1, and the airbag 2 is arranged in a two-layer package. The outer layer of the airbag 2 is provided with a protective component for support, and the inner layer of the airbag 2 is provided with two through holes, and the inner layer of the airbag 2 is in contact with the sleeve block 201;

[0039] The sleeve block 201 is hollow inside, and the size of the openings at the left and right ends thereof matches the connecting block 202. The sleeve block 201 is arranged in an arc shape, and three sleeve blocks 201 are arranged. Every two adjacent sleeve blocks 201 are connected by the connecting block 202;

[0040] The three sleeve blocks 201 and the three connection blocks 202 are connected to form a ring, and the ring is nested on the outer side of the optical fiber 101 without being attached;

[0041] The connecting block 202 is arranged in an arc shape, and the curvature of the outer side surface of the connecting block 202 matches the curvature of the inner wall of the sleeve block 201, and every two adjacent connecting blocks 202 among the three connecting blocks 202 are connected by a return spring 203;

[0042] After the housing 1 is installed, when the housing 1 is deformed by external force, the surface of the housing 1 is squeezed and the airbag 2 is compressed. When any point on the surface of the airbag 2 is subjected to external force and the pressure increases, the pressure increase is instantly transmitted to each point of the static gas, so that after the outer layer of the airbag 2 is compressed, the outer layer squeezes the inner layer, and the inner layer wraps the sleeve block 201 and squeezes the sleeve block 201. The sleeve block 201 is squeezed and shrinks inward, so that the three sleeve blocks 201 gradually accommodate the three connecting blocks 202. After moving, the three connecting blocks 202 squeeze and compress the return spring 203 at the same time. The diameter of the circular ring formed by the three compressed sleeve blocks 201 and the three connecting blocks 202 is reduced and does not fit the optical fiber, thereby preventing the housing 1 from being damaged by pressure; Example

[0043] The present embodiment is different from the embodiment 1 in that: the protection assembly comprises a protection main board 3, a protection sub-board 301, a push block 302, a push rod 303, a first fixed block 304, a connecting rod 305 and a second fixed block 306; the first fixed block 304 is mounted on the outer side of the protection main board 3; the connecting rod 305 is mounted on the bottom of the first fixed block 304; the protection sub-board 301 is mounted on the outer side of the connecting rod 305; the second fixed block 306 is mounted on one end of the connecting rod 305 away from the first fixed block 304; the push block 302 is mounted on the bottom of the second fixed block 306; and the push block 302 is mounted on one end of the push rod 303 away from the second fixed block 306;

[0044] The protective main board 3 is arranged in an arc shape and is provided with six protective main boards 3. Through holes are opened at the edges of both ends of the four middle protective main boards 3. The diameter of the through hole matches the diameter of the connecting rod 305. One of the two outermost protective main boards 3 has a through hole opened at one edge of the top end, and the other has a through hole opened at the bottom edge. Among the six protective main boards 3, every two adjacent protective main boards 3 are connected by a protective sub-board 301;

[0045] The protective sub-plate 301 is arranged in an arc shape and is inclined. Every two protective main plates 3 are connected to one protective sub-plate 301 in an "N" shape. Six protective sub-plates 301 are arranged. The edges of both ends of the middle four protective sub-plates 301 are provided with through holes matching the connecting rod 305. One of the outermost two protective sub-plates 301 has a through hole at one end edge of the top, and the other has a through hole at the bottom edge.

[0046] A push block 302, one end of the push block 302 away from the push rod 303 is connected to the outer side surface of the adjacent sleeve block 201;

[0047] Push rods 303, two push rods 303 are provided, one end of the upper push rod 303 away from the push block 302 is connected to the bottom of the protective sub-plate 301 on the middle right side, and the other end of the lower push rod 303 away from the push block 302 is connected to the top of the protective sub-plate 301 on the middle left side;

[0048] When the outer shell 1 is subjected to external force so that the airbag 2 is compressed and squeezed by the sleeve block 201, when the three sleeve blocks 201 store the three connecting blocks 202, the diameter of the ring formed by the sleeve block 201 and the connecting block 202 is reduced, so that the sleeve block 201 will move in this process, and the two sleeve blocks 201 close to the protective sub-plate 301 will drive the two push blocks 302 to move, so that after the two push blocks 302 are close to each other, the two push blocks 302 respectively pull the two middle protective main plates 3 and the protective sub-plate 301 to move through the push rod 303, and after the protective sub-plate 301 moves, every two protective main plates 3 are connected to one protective sub-plate 301, and they are all arranged in an "N" shape, so that After the protective sub-plate 301 moves, it forms an "X" shape with the protective main plate 3. After the protective sub-plate 301 is tilted, it pushes the protective main plate 3 at one end. Similarly, the six protective sub-plates 301 drive the six protective main plates 3 to move, and all of them are in an "X" shape. The protective main plate 3 and the protective sub-plates 301 are both arranged in an arc shape, so that the six protective main plates 3 and the six protective sub-plates 301 form a lantern shape after moving, and support the inner layer of the airbag 2. Therefore, after the outer shell 1 is deformed by pressure, it is supported by the protective main plate 3 and the protective sub-plate 301, thereby improving the pressure-bearing capacity of the outer shell 1, thereby improving the protection performance of the optical fiber 101, and improving the service life of the optical fiber 101. Example

[0049] The difference between this embodiment and embodiment 1 is that: the interior of the housing 1 is a liquid metal optical fiber, including a fiber core, a liquid metal cladding is attached to the fiber core, the outer layer of the liquid metal is a PVC coating layer, the liquid metal is a gallium indium tin alloy, the liquid metal is atomized and sprayed to be uniformly attached to the quartz fiber core, the atomized droplets deposited on the quartz fiber core are left to stand for a period of time and the surface is oxidized, and then the PVC layer is coated by a spraying process, and the PVC coating layer plays a protective and insulating role on the surface of the liquid metal cladding;

[0050] The liquid metal grating sensor can be used under harsh conditions such as strong electromagnetic interference, atomic radiation and chemical corrosion. Its working principle is to introduce a wide-spectrum light source from one end of the optical fiber into the incident spectrum, and the spectrum analyzer at the other end can output the reflected spectrum. The offset of the reflected spectrum relative to the incident spectrum can be converted into the change value of the strain. In geotechnical engineering, when the axial stress or radial stress changes, the transmission wavelength of the sensor will change accordingly.

[0051] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

Claims

1. A liquid metal fiber Bragg grating sensor, comprising a housing (1), characterized in that: A sealing end (103) is installed at one end of the housing (1), an optical fiber connector (102) is installed on a side of the sealing end (103) away from the housing (1), an optical fiber (101) is installed inside the housing (1), and a driving sensing component is provided on the inner wall of the housing (1), the sensing component comprising an airbag (2), a sleeve block (201), a connecting block (202) and a return spring (203); A sleeve block (201) is arranged on the inner side of the airbag (2), a connecting block (202) is arranged on one side of the sleeve block (201), and a return spring (203) is arranged inside the sleeve block (201); The inside of the shell (1) is a liquid metal optical fiber, including a fiber core, a liquid metal cladding attached to the fiber core, an outer layer of the liquid metal is a PVC coating layer, and the liquid metal is selected from a gallium indium tin alloy; The airbag (2) is filled inside the outer shell (1), the airbag (2) is arranged in a two-layer wrapped shape, the outer layer of the airbag (2) is provided with a protective component for support, the inner layer of the airbag (2) is provided with two through holes, and the inner layer of the airbag (2) is in contact with the sleeve block (201); The interior of the sleeve block (201) is hollow, and the size of the openings at the left and right ends thereof matches the connection block (202). The sleeve block (201) is arranged in an arc shape, and there are three of them, and every two adjacent sleeve blocks (201) are connected via the connection block (202); The three sleeve blocks (201) and the three connection blocks (202) are connected to form a circular ring, and the circular ring is nested on the outer side of the optical fiber (101) without being fitted; The connecting block (202) is arranged in an arc shape, the curvature of the outer side surface of the connecting block (202) matches the curvature of the inner wall of the sleeve block (201), and every two adjacent connecting blocks (202) among the three connecting blocks (202) are connected via a return spring (203).

2. A liquid metal fiber Bragg grating sensor according to claim 1, characterized in that: The protection component comprises a protection main plate (3), a protection sub-plate (301), a push block (302), a push rod (303), a first fixed block (304), a connecting rod (305) and a second fixed block (306); the first fixed block (304) is mounted on the outer side of the protection main plate (3); the connecting rod (305) is mounted on the bottom of the first fixed block (304); the protection sub-plate (301) is arranged on the outer side of the connecting rod (305); the second fixed block (306) is mounted on one end of the connecting rod (305) away from the first fixed block (304); the push block (302) is mounted on the bottom of the second fixed block (306); and the push block (302) is mounted on one end of the push rod (303) away from the second fixed block (306).

3. A liquid metal fiber Bragg grating sensor according to claim 2, characterized in that: The protective main boards (3) are arranged in an arc shape and are provided in six numbers. The four middle protective main boards (3) are provided with through holes at both end edges, and the diameter of the through holes matches the diameter of the connecting rod (305). The two outermost protective main boards (3) are provided with a through hole at one end edge of the top, and a through hole at the other end edge of the bottom. Among the six protective main boards (3), every two adjacent protective main boards (3) are connected via a protective sub-board (301).

4. A liquid metal fiber Bragg grating sensor according to claim 3, characterized in that: The protective sub-plates (301) are arranged in an arc shape and are arranged in an inclined manner. Every two protective main plates (3) are connected to a protective sub-plate (301) in an "N" shape. Six protective sub-plates (301) are arranged, and through holes matching the connecting rods (305) are opened at the edges of both ends of the four middle protective sub-plates (301). One of the two outermost protective sub-plates (301) has a through hole opened at one end edge of the top, and the other has a through hole opened at the bottom edge.

5. The liquid metal fiber Bragg grating sensor according to claim 2, characterized in that: One end of the push block (302) away from the push rod (303) is connected to the outer side surface of the adjacent sleeve block (201), and two push rods (303) are provided. One end of the upper push rod (303) away from the push block (302) is connected to the bottom of the protective sub-plate (301) on the right side in the middle, and one end of the lower push rod (303) away from the push block (302) is connected to the top of the protective sub-plate (301) on the left side in the middle.

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