Liquid metal fiber grating sensor array and its protection device and construction method

Abstract

The present invention provides a liquid metal fiber grating sensor array and its protective device and construction method, including a distributor, a protective hose and an optical fiber, the outer wall of the distributor is closely attached to the protective hose, the optical fiber is embedded in the protective hose, the protective sheet is embedded in the protective hose, the fiber grating sensor is fixed to the outside of the optical fiber, the fiber grating sensor is made of liquid metal optical fiber, the liquid metal is atomized and evenly sprayed on the fiber core, the atomized droplets deposited on the fiber core are left to stand for a period of time and the surface is oxidized, and then a PVC layer is coated by a spraying process. During use of the present invention, the liquid metal cladding of the optical fiber has good flexibility and waterproofness, the protective hose of the protective component of the outer wall of the fiber grating sensor will automatically return to its position after bending and stretching, has good tensile and bending resistance, has a good protection effect on the optical fiber and the fiber grating sensor, and further improves the service life of the optical fiber and the fiber grating sensor.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, and in particular to a liquid metal fiber grating sensor array and a protective device and a construction method thereof. Background Art

[0002] At present, fiber Bragg grating sensing technology has been widely used in the field of building structure health monitoring due to its superior anti-electromagnetic interference, electrical insulation, corrosion resistance, small size, low transmission loss, and large transmission capacity. However, during the implementation of the project, the installation and protection of fiber Bragg grating sensors and optical cables are the first-line construction links, facing the harsh civil construction environment. Effective protection measures and construction technology are important guarantees for the long-term stable operation of the system. The core component of the fiber Bragg grating sensor is a section of fiber Bragg grating located on the bare optical fiber. The bare optical fiber itself is fragile and easy to break. To improve the environmental adaptability and service life of the fiber Bragg grating sensor, it is fundamentally to improve the environmental adaptability and long-term working stability of the optical fiber. The factors that affect the service life of the optical fiber are: 1. There are microcracks on the surface of the optical fiber, and the material itself is not flexible enough, which increases the risk of breakage; 2. Water and water vapor molecules in the atmospheric environment will corrode the surface of the optical fiber, and its mechanical and corrosion resistance have hidden dangers; 3. The long-term effect of residual stress when the optical cable is laid unreasonably; 4. The existing fiber Bragg grating multi-section fusion connection and grating notch are easy to wear, which will lead to inaccurate data for long-distance transmission.

[0003] Therefore, the prior art proposes a patent number CN201710467727.4 for an optical fiber grating sensor array for underground construction and its protective device and construction method, which provides a series of protections for optical fiber such as anti-vibration, anti-impact, anti-extrusion, and waterproof, and improves the material and process of the optical fiber itself. In the axial direction, the triple loose tube structure enables the single-mode single-core armored optical cable to have excellent anti-traction ability; the protection scheme of the optical fiber fusion point provides triple anti-bending protection for the fusion point.

[0004] However, when this type of device is actually used, due to the placement of a collimation sleeve at the junction of the armored optical cable and the crimping terminal, the armored optical cable will bend at the same time when the optical fiber is bent. When the optical fiber is bent to a large extent, it is easy to cause the armor sheet inside the armored optical cable to bend and be unable to reset, causing the optical fiber inside to be in a bent state for a long time, and the anti-bending and anti-stretching effects are poor. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a liquid metal fiber grating sensor array and a protective device and a construction method thereof to solve the problems described in the above background technology.

[0006] The present invention provides a liquid metal fiber grating sensor array and its protective device and construction method, which are achieved by the following specific technical means: a liquid metal fiber grating sensor array and its protective device, including a distributor, a protective hose and an optical fiber, the outer wall of the distributor is tightly attached to the protective hose, the interior of the protective hose is embedded with an optical fiber, the interior of the protective hose is embedded with a protective sheet, the outside of the optical fiber is fixed with a fiber grating sensor, the optical fiber of the fiber grating sensor adopts a liquid metal cladding, and the outer wall of the fiber grating sensor is provided with a protective component.

[0007] As a further solution of the present invention: a plurality of protective sheets are equidistantly embedded in the interior of the protective hose, the outer walls of the protective sheets are closely attached to the inner wall of the protective hose, and the spacing between adjacent protective sheets at the left and right ends is 2-3 cm.

[0008] As a further solution of the present invention: a connecting belt and a buffer spring are connected between the adjacent protective sheets at the left and right ends, the connecting belt is made of elastic material, and the buffer spring and the connecting belt are arranged in a circular ring around the middle of the protective hose.

[0009] As a further solution of the present invention: the liquid metal selected for the optical fiber cladding of the liquid metal grating sensor is gallium indium tin alloy, which is non-toxic, non-corrosive and highly flexible. Liquid metal easily forms gallium oxide at room temperature, and its film is easy to solidify and the refractive index and light transmittance increase, which meets the conditions for total reflection of optical fiber, and its own metal characteristics have the advantages of reducing light wave loss and improving light wave transmission efficiency.

[0010] As a further solution of the present invention: if the output of the optical fiber manufacturing of the liquid metal grating sensor is low, a layered process is adopted, and a metal atomization spray forming technology is used on an extremely fine fiber core to naturally combine the atomization of the liquid metal and the deposition of the atomized droplets, which are completed in a one-step operation, and the liquid metal is directly and densely attached to the fiber core as a whole with a minimum of steps. In addition, the spray molding refines the grain structure of the liquid metal, and the tensile strength and plasticity of the optical fiber are significantly improved. A spraying process is used on the liquid metal cladding to protect and isolate the surface of the liquid metal film. The plastic powder is charged by a high-voltage electrostatic device and sprayed on the optical fiber under the action of the electric field. The powder will be evenly adsorbed to form a powdery coating. The final protective coating is very dense and effectively isolates water and other harmful substances.

[0011] As a further solution of the present invention: if the optical fiber manufacturing of the liquid metal grating sensor has a high output, a preform rod process is adopted, that is, a material preform for drawing the optical fiber is first manufactured, and then the core, cladding and coating layer materials are injected into the preform, and finally a complete optical fiber can be obtained through a wire drawing mechanical equipment. The length of the optical fiber produced by this manufacturing process can reach tens to hundreds of kilometers.

[0012] As a further solution of the present invention: the distributor is connected to the programmable optical switch through a trunk optical cable. The programmable optical switch is controlled by the control host to open the corresponding transmission channel at a specific timing. Then the optical signal reaches the fiber grating demodulator through the coupler, is demodulated and converted into an electrical signal, and is transmitted to the control host according to the specified communication protocol.

[0013] As a further solution of the present invention: the protection assembly is composed of a protection cylinder, an inner cylinder, a limiting protrusion, an inner connecting cylinder, a buffer cylinder, an extension column, a spring, an outer cylinder, an outer connecting cylinder and a support ring;

[0014] Specifically, a protective tube is nested in the outer wall of the optical fiber, an inner tube body is fixed in the middle of the protective tube, a limiting protrusion is fixed on the inner wall of the inner tube body, inner connecting tubes are transversely embedded in the left and right ends of the interior of the protective tube, a buffer tube is transversely embedded in the inner outer side of the inner connecting tube, an extension column and a spring are embedded in the interior of the protective tube, an outer tube body is embedded in the inner outer side of the inner connecting tube, an outer connecting tube is nested in the inner outer side of the outer tube body, and support rings are fixed on the left and right ends of the outer wall of the protective tube.

[0015] As a further solution of the present invention: the two external connecting tubes are symmetrically arranged around the longitudinal center axis of the protective tube, and the outer sides of the external connecting tubes are embedded in the interior of the protective hose and connected to the protective sheet.

[0016] As a further solution of the present invention: the outer connecting tube is connected to the outer cylinder body via threads, and the outer wall of the outer cylinder body is connected to the inner wall of the inner connecting tube via threads.

[0017] As a further solution of the present invention: the outer side of the extension column is connected to the inner connecting tube, the spring is nested in the outer side of the extension column, and the inner connecting tube slides horizontally left and right inside the protective tube.

[0018] As a further solution of the present invention: the limiting protrusions are arranged in a circular ring shape around the middle of the inner cylinder, and the limiting protrusions are made of rubber material.

[0019] As a further solution of the present invention: specifically, the following steps are also included:

[0020] S1: The inner cylinder of the protective cylinder is nested on the outer side of the optical fiber. At this time, the limiting protrusion is close to the outer wall of the optical fiber so that the optical fiber is in the middle of the inner cylinder, ensuring the parallelism between the optical fiber and the inner cylinder;

[0021] S2: After sealing the inner cylinder at one end, inject an appropriate amount of heated epoxy resin into the inner cylinder through the other end of the inner cylinder, and then seal the other end of the inner cylinder to achieve packaging and fixing of the fiber grating sensor;

[0022] S3: twist the outer cylinder to embed it into the buffer cylinder, and then twist the external connecting cylinder to embed it into the outer cylinder;

[0023] S4: Finally, the other end of the optical fiber is connected to the distributor, thus completing the array of the fiber grating sensor 402.

[0024] 1. When the protective hose outside the optical fiber is subjected to tensile force, the protective hose pulls the inner tube to slide in the protective tube through the outer tube and the outer cylinder body, so that the inner tube moves to the outside of the protective tube. Since one end of the inner tube is connected to the extension column at one end of the buffer tube, the extension column moves outward in the buffer tube to squeeze the spring deformation on the outside thereof. The tensile force exerted on the protective hose is buffered by the deformation of the spring, which has a better protective effect on the optical fiber and further improves the tensile resistance of the device.

[0025] 2. When the optical fiber is bent under force, the protective hose outside the optical fiber is bent at the same time, so that there is a certain angle between the adjacent protective sheets in the protective hose and they are tilted. At this time, the buffer spring and the connecting belt between the two protective sheets are deformed under force to produce a rebound force. The higher the bending degree of the protective hose, the greater the rebound force generated by the buffer spring and the connecting belt, which can prevent the optical fiber from further bending. When the optical fiber is not affected by external force, the rebound force generated by the buffer spring and the connecting belt will push the protective sheet and the protective hose to return to their original position, which has a better protection effect on the optical fiber and the fiber grating sensor, and further improves the anti-bending performance of the protective hose.

[0026] 3. When the optical fiber is subjected to more stretching and bending, the liquid metal optical fiber has a larger bending radius and better mechanical strength due to the flexibility of the liquid metal cladding. When the optical fiber is in an environment with high humidity or corrosive liquids, the cladding of the liquid metal optical fiber can better isolate water and other harmful substances, broaden the application environment and increase the service life. In complex construction environments, the liquid metal cladding can reduce the degree of light loss and make the periodic transmission of light waves more accurate. The liquid metal grating adopts a femtosecond direct writing process and can directly pass through the coating layer and cladding. The stripe visibility is large, the grating is extended to a longer length, and no more multi-section melting is required, which further prevents the possibility of optical fiber breakage or unsuitability for complex construction environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0028] Figure 2 It is a front cross-sectional schematic diagram of the local structure of the protective tube in the present invention;

[0029] Figure 3 It is a schematic diagram of the explosion of the local structure of the protective tube in the present invention;

[0030] Figure 4It is a front cross-sectional schematic diagram of the local structure of the inner cylinder in the present invention;

[0031] Figure 5 It is a front cross-sectional schematic diagram of the local structure of the protective hose in the present invention;

[0032] Figure 6 It is a schematic diagram of the partial structure of the protection sheet in the present invention;

[0033] Figure 7 It is a schematic diagram of the local structure of the connecting belt and the buffer spring in the present invention.

[0034] Legend:

[0035] Distributor 1, protective hose 2, protective sheet 201, connecting belt 202, buffer spring 203, optical fiber 3, protective tube 4, inner cylinder 401, fiber optic grating sensor 402, limiting protrusion 403, inner connecting tube 404, buffer tube 405, extension column 406, spring 407, outer cylinder 408, outer connecting tube 409, support ring 410. Implementation

[0036] Example 1, please refer to Figure 1-7 A liquid metal fiber Bragg grating sensor array and a protective device thereof, comprising a distributor 1, a protective hose 2 and an optical fiber 3, the outer wall of the distributor 1 is closely attached to the protective hose 2, the inner part of the protective hose 2 is embedded with the optical fiber 3, the inner part of the protective hose 2 is embedded with a protective sheet 201, the outer part of the optical fiber 3 is fixed with a fiber Bragg grating sensor 402, the optical fiber of the fiber Bragg grating sensor 402 adopts a liquid metal cladding, and the outer wall of the fiber Bragg grating sensor 402 is provided with a protective component;

[0037] Several protective sheets 201 are equidistantly embedded in the protective hose 2. The outer walls of the protective sheets 201 are closely attached to the inner wall of the protective hose 2. The spacing between the adjacent protective sheets 201 at the left and right ends is 2-3 cm.

[0038] Since there is a certain distance between adjacent protection sheets 201, when the protection hose 2 is bent, the adjacent protection sheets 201 will not be squeezed against each other as the protection hose 2 is bent;

[0039] A connecting belt 202 and a buffer spring 203 are connected between the adjacent protection sheets 201 at the left and right ends. The connecting belt 202 is made of elastic material. The buffer spring 203 and the connecting belt 202 are arranged in a circular ring around the middle of the protection hose 2.

[0040] When the optical fiber 3 is bent under stress, the protective hose 2 outside the optical fiber 3 is bent at the same time, so that there is a certain angle between the adjacent protective sheets 201 in the protective hose 2 and they are tilted. At this time, the buffer spring 203 and the connecting belt 202 between the two protective sheets 201 are deformed under stress to generate a rebound force. The higher the bending degree of the protective hose 2, the greater the rebound force generated by the buffer spring 203 and the connecting belt 202, which can prevent the optical fiber from further bending. When the optical fiber is not affected by external forces, the rebound force generated by the buffer spring 203 and the connecting belt 202 will push the protective sheet 201 and the protective hose 2 to return to their original positions, which has a better protection effect on the optical fiber 3 and further improves the anti-bending performance of the protective hose 2.

[0041] The distributor 1 is connected to the program-controlled optical switch through the trunk optical cable. The program-controlled optical switch is controlled by the control host to open the corresponding transmission channel at a specific time sequence. Then the optical signal reaches the fiber grating demodulator through the coupler, is demodulated and converted into an electrical signal, and is transmitted to the control host according to the specified communication protocol;

[0042] After the broadband light source is generated, it passes through the coupler, programmable optical switch, distributor 1, trunk optical cable, single-mode single-core armored optical cable, and is transmitted to the test channel. Both ends of the test channel can receive the broadband light source. Then, each fiber optic Bragg grating sensor 402 generates a specific wavelength modulated optical signal and reflects it back along the original path. The optical signal reaches the programmable optical switch through the optical fiber 3, distributor 1 and trunk optical cable. The programmable optical switch is controlled by the control host to open the corresponding transmission channel at a specific timing. Then, the optical signal reaches the fiber optic Bragg grating demodulator through the coupler, is demodulated and converted into an electrical signal, and is transmitted to the control host according to the specified communication protocol. The control host 10 performs a series of processing operations such as analysis, judgment, and storage on the data.

[0043] Example 2, please refer to Figure 1-7 , Embodiment 2 is different from Embodiment 1 in that the protection assembly is composed of a protection cylinder 4, an inner cylinder 401, a limiting protrusion 403, an inner connecting cylinder 404, a buffer cylinder 405, an extension column 406, a spring 407, an outer cylinder 408, an outer connecting cylinder 409 and a support ring 410;

[0044] The outer wall of the optical fiber 3 is embedded with a protective tube 4, an inner tube body 401 is fixed in the middle of the protective tube 4, a limiting protrusion 403 is fixed on the inner wall of the inner tube body 401, an inner tube 404 is transversely embedded in the left and right ends of the inside of the protective tube 4, a buffer tube 405 is transversely embedded in the inner and outer sides of the inner tube 404, an extension column 406 and a spring 407 are embedded in the inside of the protective tube 4, an outer tube body 408 is embedded in the inner and outer sides of the inner tube 404, an outer tube 409 is nested in the inner and outer sides of the outer tube body 408, and support rings 410 are fixed on the left and right ends of the outer wall of the protective tube 4;

[0045] The two external connecting tubes 409 are symmetrically arranged around the longitudinal center axis of the protective tube 4, and the outer sides of the external connecting tubes 409 are embedded in the interior of the protective hose 2 and connected to the protective sheet 201;

[0046] The outer connecting tube 409 is connected to the outer cylinder body 408 via threads, and the outer wall of the outer cylinder body 408 is connected to the inner wall of the inner connecting tube 404 via threads;

[0047] When the outer cylinder 408 rotates clockwise, the outer cylinder 408 is fixed together with the inner cylinder 404 and the outer cylinder 409, and when the outer cylinder 408 rotates counterclockwise, the outer cylinder 408 is separated from the inner cylinder 404 and the outer cylinder 409 at the same time;

[0048] By loosening the outer cylinder 408, the outer cylinder 409 and the inner cylinder 404 can be disassembled;

[0049] The outer side of the extension column 406 is connected to the inner tube 404, the spring 407 is nested on the outer side of the extension column 406, and the inner tube 404 slides horizontally left and right inside the protective tube 4;

[0050] When the protective hose 2 outside the optical fiber 3 is subjected to a tensile force, the protective hose 2 pulls the inner tube 404 to slide in the protective tube 4 through the outer tube 409 and the outer cylinder 208, so that the inner tube 404 moves to the outside of the protective tube 4. Since one end of the inner tube 4 is connected to the extension column 406 at one end of the buffer tube 405, the extension column 406 moves outward in the buffer tube 405 to squeeze the spring 407 on its outside to deform. The tensile force exerted on the protective hose is buffered by the deformation of the spring 407, which has a better protective effect on the optical fiber and further improves the tensile resistance of the device.

[0051] The limiting protrusions 403 are arranged in a circular ring around the middle of the inner cylinder 401, and the limiting protrusions 403 are made of rubber material;

[0052] Among them, the main function of the limiting protrusion 403 is that when the inner cylinder 401 is nested outside the optical fiber 3, the optical fiber 3 will be horizontally located in the middle of the inner cylinder 401, allowing the optical fiber 3 to be suspended and facilitating the subsequent injection of epoxy resin into the inner cylinder 401.

[0053] Example 3, please refer to Figure 1-7 The difference between Example 3 and Example 2 is that it further includes the following steps:

[0054] S1: The inner cylinder 401 of the protective cylinder 4 is nested outside the optical fiber 3. At this time, the limiting protrusion 403 is close to the outer wall of the optical fiber 3 so that the optical fiber 3 is in the middle of the inner cylinder 401, ensuring the parallelism between the optical fiber 3 and the inner cylinder 401;

[0055] S2: After sealing the inner cylinder 401 at one end, inject a proper amount of heated epoxy resin into the inner cylinder 401 through the other end of the inner cylinder 401, and then seal the other end of the inner cylinder 401 to achieve packaging and fixing of the fiber grating sensor 402;

[0056] S3: twist the outer cylinder 408 to embed it into the buffer cylinder 405, and then twist the external connection cylinder 409 to embed it into the outer cylinder 408;

[0057] S4: Finally, the other end of the optical fiber 3 is connected to the distributor 1, thus completing the array of the fiber grating sensor 402.

[0058] In Example 4, the optical fiber 3 atomizes the liquid metal and sprays it to evenly attach it to the fiber core. After the atomized droplets deposited on the fiber core are left to stand for a period of time and the surface is oxidized, a PVC layer is coated by a spraying process. The PVC coating layer protects and isolates the surface of the liquid metal cladding.

[0059] The liquid metal optical fiber 3 lists a method for manufacturing a liquid metal fiber grating sensor, which specifically includes the following steps:

[0060] S1: Place the liquid metal fiber on the translation stage, and align the CCD, half-reflective half-mirror, and microscope on it one by one;

[0061] S2: The femtosecond laser is controlled by an electrically controlled shutter, and after light attenuation control and polarization control, it can directly penetrate the PVC coating layer through the precise movement of the translation stage. A uniform grating with a constant period is engraved on the surface of the quartz fiber core, and the grating does not damage the PVC coating and liquid metal cladding.

[0062] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A liquid metal fiber Bragg grating sensor array and a protective device thereof, comprising a distributor (1), a protective hose (2) and an optical fiber (3), wherein the outer wall of the distributor (1) is in close contact with the protective hose (2), and the optical fiber (3) is embedded in the interior of the protective hose (2), characterized in that: A protective sheet (201) is embedded in the protective hose (2), a fiber grating sensor (402) is fixed to the outside of the optical fiber (3), the optical fiber of the fiber grating sensor (402) adopts a liquid metal cladding, and a protective component is arranged on the outer wall of the fiber grating sensor (402); A plurality of protective sheets (201) are equidistantly embedded in the interior of the protective hose (2), the outer walls of the protective sheets (201) are closely attached to the inner wall of the protective hose (2), and the spacing between adjacent protective sheets (201) at the left and right ends is 2-3 cm; A connecting belt (202) and a buffer spring (203) are connected between the adjacent protection sheets (201) at the left and right ends, the connecting belt (202) is made of elastic material, and the buffer spring (203) and the connecting belt (202) are arranged in a circular ring around the middle of the protection hose (2); The distributor (1) is connected to the programmable optical switch via a trunk optical cable. The programmable optical switch is controlled by the control host to open the corresponding transmission channel at a specific time sequence. Then the optical signal reaches the fiber optic Bragg grating demodulator through the coupler, is demodulated and converted into an electrical signal, and is transmitted to the control host according to a specified communication protocol. The protection assembly is composed of a protection cylinder (4), an inner cylinder (401), a limiting protrusion (403), an inner connecting cylinder (404), a buffer cylinder (405), an extension column (406), a spring (407), an outer cylinder (408), an outer connecting cylinder (409) and a support ring (410); A protective tube (4) is embedded in the outer wall of the optical fiber (3); an inner tube body (401) is fixed in the middle of the protective tube (4); a limiting protrusion (403) is fixed on the inner wall of the inner tube body (401); an inner tube (404) is transversely embedded in the left and right ends of the inside of the protective tube (4); a buffer tube (405) is transversely embedded in the inner and outer sides of the inner tube body (401); an extension column (406) and a spring (407) are embedded in the buffer tube (405); an outer tube body (408) is embedded in the inner and outer sides of the inner tube (404); an outer tube (409) is embedded in the inner and outer sides of the outer tube body (408); and support rings (410) are fixed to the left and right ends of the outer wall of the protective tube (4); The optical fiber (3) atomizes the liquid metal and sprays it to evenly attach it to the fiber core. After the atomized molten droplets deposited on the fiber core are left to stand for a period of time and the surface is oxidized, a PVC layer is coated on the liquid metal cladding by a spraying process. The liquid metal cladding meets the conditions for total reflection and plays a protective and insulating role together with the PVC coating layer. The two external connecting tubes (409) are symmetrically arranged around the longitudinal center axis of the protective tube (4), and the outer sides of the external connecting tubes (409) are embedded in the interior of the protective hose (2) and connected to the protective sheet (201); The outer connecting tube (409) and the outer cylinder body (408) are connected via threads, and the outer wall of the outer cylinder body (408) and the inner wall of the inner connecting tube (404) are connected via threads; The outer side of the extension column (406) is connected to the inner tube (404), the spring (407) is nested on the outer side of the extension column (406), the inner tube (404) slides horizontally left and right inside the protective tube (4), the limiting protrusions (403) are arranged in a circular ring around the middle of the inner tube body (401), and the limiting protrusions (403) are made of rubber material; The specific construction method also includes the following steps: S1: The inner cylinder (401) of the protective cylinder (4) is nested on the outer side of the optical fiber (3), and the limiting protrusion (403) is in close contact with the outer wall of the optical fiber (3) so that the optical fiber (3) is located in the middle of the inner cylinder (401), thereby ensuring that the optical fiber (3) and the inner cylinder (401) are parallel to each other; S2: After sealing the inner cylinder (401) at one end, injecting a suitable amount of heated epoxy resin into the inner cylinder (401) through the other end of the inner cylinder (401), and then sealing the other end of the inner cylinder (401) to achieve packaging and fixing of the fiber optic Bragg grating sensor (402); S3: twisting the outer cylinder (408) to embed it into the inner cylinder (404), and then twisting the outer cylinder (409) to embed it into the outer cylinder (408); S4: Finally, the other end of the optical fiber (3) is connected to the distributor (1), thereby completing the array of the fiber grating sensor 402.

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