All-metal high-temperature-resistant fiber grating sensor and preparation method thereof

Abstract

The application provides a full-metal packaging high-temperature-resistant fiber grating sensor and a preparation method thereof. In the preparation, one of titanium or chromium and a nickel layer are deposited on a fiber grating to-be-plated section, an auxiliary conductive pipe with a bevel is sleeved on a non-plated section position, a flexible metal wire is electrically connected with the nickel layer and axial tension is applied by bending and plastic shaping, then the to-be-plated section is placed in an electroplating liquid and the auxiliary conductive pipe is kept above the liquid surface, a nickel metal protective layer is formed by primary low-current electro-deposition under constant low current; edge fillet transition and local plating resistance treatment are performed on a metal base with an assembly groove; the fiber grating is embedded in the assembly groove and is fixedly connected by secondary electro-deposition, and the fiber grating sensor is obtained. The application solves the double-wave peak problem of the fiber grating sensor by optimizing the conductive straightening structure, implementing liquid surface physical isolation and eliminating the base mutation, and improves the yield of the finished product.

Description

Technical Field

[0001] This invention relates to the field of all-metal packaged high-temperature resistant fiber Bragg grating sensor technology, specifically to an all-metal packaged high-temperature resistant fiber Bragg grating sensor and its fabrication method. Background Technology

[0002] Existing high-temperature metallization packaging methods for fiber Bragg grating sensors typically involve depositing a conductive layer on the fiber surface, followed by electroplating to thicken it, and finally fixing it onto a support structure (metal substrate). However, the yield of sensors packaged using existing methods is low, approximately only 50%. A Hippo demodulator can detect dual peaks (also known as peak splitting), while a good sensor should exhibit a single usable peak. Therefore, there is a strong need to improve the fabrication method to increase the yield. Summary of the Invention

[0003] This invention provides an all-metal packaged high-temperature resistant fiber Bragg grating sensor and its fabrication method to solve the problem of low yield in the prior art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for fabricating a high-temperature resistant fiber Bragg grating sensor with all-metal encapsulation, the method comprising the following steps: S1. Undercoating: A fiber grating body having a section to be coated and a non-coated section located on at least one side of the section to be coated along its axial direction is provided. Physical vapor deposition is performed sequentially on the outer surface of the section to be coated to form an adhesive layer and a nickel metal conductive layer, wherein the adhesive layer is titanium metal or chromium metal. S2. Tooling Limiting and Tensioning Assembly: An auxiliary conductive tube with a beveled end is fitted onto the non-plated section; the auxiliary conductive tube is held stationary by the holding structure of the supporting base; one end of a flexible metal wire is physically fixed and electrically connected to the nickel metal conductive layer, and the other end of the flexible metal wire is connected to the auxiliary conductive tube. By bending and shaping the flexible metal wire, the fixed auxiliary conductive tube serves as a mechanical force fulcrum, and a tensioning and straightening force is applied along the axial direction of the fiber grating body. S3. Initial low-current electrodeposition: The section to be plated of the fiber grating body assembled in step S2 is placed in the electroplating solution, and the auxiliary conductive tube is kept 1-3 mm above the surface of the electroplating solution. Current is conducted through the flexible metal wire and the auxiliary conductive tube, and electrodeposition is performed under a constant current condition of 0.015-0.03A to form a dense nickel metal protective layer on the surface of the section to be plated. S4. Substrate anti-discharge and resist plating treatment: A metal substrate with an assembly groove on its surface is provided. The outer contour edge of the metal substrate and the groove opening edge of the assembly groove are rounded to eliminate geometric abrupt changes. The surface of the metal substrate is covered with resist plating paint and heated to cure. Then, a slit is opened in the area corresponding to the assembly groove along the extension direction of the assembly groove to expose part of the inner wall of the assembly groove. S5. Secondary embedding electrodeposition: The fiber grating body processed in step S3 is taken out from the auxiliary conductive tube and embedded in the assembly groove of the metal substrate processed in step S4. It is placed in the electroplating solution and subjected to secondary electrodeposition under a constant current of 0.02 to 0.03 A, so that the deposited nickel metal fills the assembly groove and fixes the fiber grating body to the metal substrate.

[0005] To achieve the above objectives, the present invention also provides the following technical solutions: A high-temperature resistant fiber Bragg grating sensor with all-metal encapsulation is disclosed. The sensor is fabricated by the above-described method. The sensor includes a metal substrate and a metallized fiber Bragg grating embedded and fixed in an assembly groove of the metal substrate. The groove opening edge and the outer contour edge of the metal substrate are both rounded. A dense nickel metal layer formed by electrodeposition is filled between the metallized fiber Bragg grating and the assembly groove.

[0006] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. Achieved high yield through physical isolation and anti-adhesion demolding: During the initial low-current electrodeposition, an auxiliary conductive tube with a bevel structure is used in conjunction with a flexible metal wire. By bending and shaping the flexible metal wire, an axial tension straightening force is applied to the ultra-fine optical fiber, avoiding fiber deformation. At the same time, the auxiliary conductive tube is strictly controlled to be placed above the electroplating liquid surface, which completely isolates the ultra-fine optical fiber from the risk of uncontrollable metal adhesion to the inner wall of the auxiliary conductive tube during electrodeposition, thus preventing fiber breakage. This process solves the double-peak problem of existing technologies and improves the yield of packaged products to over 90%.

[0007] 2. Improved coating density and long-term reliability: The use of extremely low current constant current electrodeposition conditions (0.015–0.03 A) significantly slows down the electrochemical reduction kinetics. This condition makes the growth of nickel metal grains more balanced and dense, suppresses stress accumulation, eliminates coating cracking and hydrogen embrittlement at the physical level, and improves the mechanical stability of the sensor under extreme environments.

[0008] 3. Optimized electric field distribution eliminates morphological defects: By rounding the outer contour of the metal substrate and the groove opening, and using a resist coating layer with precisely slits, the electric field gradient in the assembly groove area is artificially controlled. This structure eliminates tip discharge, ensuring uniform reduction of metal ions during secondary electrodeposition, resulting in a high-quality packaged product with a smooth appearance and nodules. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of the structure of the improved metal substrate in an embodiment of the present invention; Figure 2 This is a schematic diagram of the copper wire connection during electroplating in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure for applying resist coating and cutting slits in an embodiment of the present invention; Figure 4 This is a schematic diagram of the cross-sectional structure of the all-metal packaged fiber Bragg grating sensor in an embodiment of the present invention; Figure 5 This is the bevel structure of the auxiliary conductive tube in an embodiment of the present invention.

[0011] Explanation of reference numerals in the attached figures 1-Fiber Bragg grating body; 11-Section to be plated; 12-Unplated section; 2-Adhesive layer; 3-Nickel metal conductive layer; 5-Auxiliary conductive tube; 51-Bevel structure; 6-Flexible metal wire; 7-Nickel metal protective layer; 8-Metal substrate; 81-Outer contour edge; 82-Assembly groove; 83-Groove edge; 9-Resistant coating; 91-Slit; 10-Metallized fiber Bragg grating; 13-Dense nickel metal layer; 14-Support base component; 141-Fixing structure. Detailed Implementation

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0013] Any specific numerical value (including the endpoints of the numerical range) disclosed in this invention is not limited to the exact value, but should be understood to also cover values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, for the disclosed numerical range, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values. These new numerical ranges should also be considered as specifically disclosed in this invention.

[0014] The terminology used in this invention is for the purpose of describing specific exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used herein are intended to include multiple forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and thus describe the presence of said features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. Although the open-ended term “comprising” should be understood as a non-limiting term used to describe and claim the various embodiments described in this invention, in some aspects it may instead be understood as a more restrictive and limiting term, such as “consisting of” or “essentially composed of.” Thus, for any given embodiment describing compositions, materials, components, elements, features, integers, operations, and / or method steps, the invention also particularly includes embodiments consisting of or substantially consisting of such compositions, materials, components, elements, features, integers, operations, and / or method steps. In the case of “consisting of…”, alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operating and / or method steps. In the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operating and / or method steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operating and / or method steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0015] Any method steps, procedures, and operations described in this invention should not be construed as necessarily requiring them to be performed in the specific order discussed or shown, unless explicitly specified. It should also be understood that, unless otherwise stated, additional or alternative steps may be used.

[0016] In this invention, except where expressly stated, any matters or issues not mentioned are directly applicable to those known in the art without any modification. Furthermore, any embodiment described in this invention can be freely combined with one or more other embodiments described in this invention, and the resulting technical solutions or concepts are considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed or anticipated by this invention, unless those skilled in the art consider the combination to be clearly unreasonable.

[0017] Unless otherwise stated, the terminology used in this invention has the same meaning as commonly understood by those skilled in the art. If a term is defined in this invention and its definition differs from the common understanding in the art, the definition of this invention shall prevail.

[0018] First aspect See Figures 1 to 5This invention provides a method for fabricating a high-temperature resistant fiber Bragg grating sensor with all-metal encapsulation. The method includes the following steps: S1, undercoating: A fiber Bragg grating body 1 is provided, having a section to be coated 11 along its axial direction and a non-coated section 12 located on at least one side of the section to be coated 11. Physical vapor deposition is performed sequentially on the outer surface of the section to be coated 11 to form an adhesive layer 2 and a nickel metal conductive layer 3, wherein the adhesive layer 2 is titanium metal or chromium metal; S2, tooling limiting and tensioning assembly: An auxiliary conductive tube 5 with a bevel structure 51 at one end is fitted onto the non-coated section 12. The auxiliary conductive tube 5 is fixed and held in place by the holding structure 141 of the supporting base 14; one end of the flexible metal wire 6 is physically fixed and electrically connected to the nickel metal conductive layer 3, and the other end of the flexible metal wire 6 is connected to the auxiliary conductive tube 5. By bending and shaping the flexible metal wire 6, the fixed auxiliary conductive tube 5 is used as a mechanical force fulcrum to apply a tension straightening force along the axial direction of the fiber grating body 1; S3, initial low-current electrodeposition: the section 11 to be plated of the fiber grating body 1 assembled in step S2 is placed in the electroplating solution and kept in place. The auxiliary conductive tube 5 is positioned 1-3 mm above the surface of the electroplating solution. Current is conducted through the flexible metal wire 6 and the auxiliary conductive tube 5, and electrodeposition is performed under a constant current condition of 0.015-0.03A to form a dense nickel metal protective layer 7 on the surface of the section to be plated 11; S4, substrate anti-discharge and anti-plating treatment: A metal substrate 8 with an assembly groove 82 on its surface is provided. The outer contour edge 81 of the metal substrate 8 and the groove opening edge 83 of the assembly groove 82 are rounded to eliminate geometric abrupt changes; an anti-plating paint 9 is applied to the surface of the metal substrate 8. The material is heated and cured, and then a slit 91 extending along the assembly groove 82 is opened in the area corresponding to the assembly groove 82, exposing part of the inner wall of the assembly groove 82; S5, secondary embedding electrodeposition: the fiber grating body 1 processed in step S3 is taken out from the auxiliary conductive tube 5 and embedded in the assembly groove 82 of the metal substrate 8 after step S4, and placed in the electroplating solution. Secondary electrodeposition is performed under a constant current condition of 0.02 to 0.03 A, so that the deposited nickel metal fills the assembly groove 82 and fixes the fiber grating body 1 to the metal substrate 8.This invention employs an auxiliary conductive tube 5 with a bevel structure 51 in conjunction with a flexible metal wire 6 for conduction. It also utilizes a process involving bending and shaping the flexible metal wire 6 to apply axial tension and straightening force, placing the auxiliary conductive tube 5 above the liquid surface for extremely low-current constant-current electrodeposition, and a combination of steps including rounding the outer contour edge 81 and groove edge 83 of the metal substrate 8 and applying resist plating by precisely slitting 91. This comprehensive approach achieves axial straightening of the micro-fiber body during electrodeposition, completely isolating the metal tube wall from the liquid-phase electrodeposition environment in physical space. This significantly homogenizes the gradient distribution of the substrate's electric field, thereby solving a series of manufacturing defects in existing processes, such as the double-peak problem, easy adhesion of the tube wall metal leading to fiber breakage and demolding failure, excessively fast current causing high internal stress in the coating leading to hydrogen embrittlement and cracking, and tip discharge at abrupt changes in substrate geometry resulting in surface metal nodules.

[0019] See Figure 4 In some embodiments of the present invention, in step S1, physical vapor deposition employs magnetron sputtering. When sputtering the adhesive layer 2, the power is set to 100–140 W, the pressure to 0.7–1.0 Pa, and the sputtering time to 25–35 minutes. It is worth noting that regardless of whether the adhesive layer 2 is made of titanium or chromium, the sputtering process parameters are as described above. When sputtering the nickel conductive layer 3, the power is set to 100–140 W, the pressure to 0.7–1.0 Pa, and the sputtering time to 25–35 minutes. By limiting the specific environmental parameters of the magnetron sputtering process to prepare the adhesive layer 2 and the nickel conductive layer 3, atomically dense film quality and excellent interfacial adhesion of the underlying metal film are achieved. This solves the problem of insufficient adhesion of the base coating leading to peeling or poor conductivity causing plating failure during subsequent lengthy electroplating processes.

[0020] See Figure 2 In some embodiments of the present invention, in step S2, the bevel structure 51 is a notch extending 5mm along the axial direction of the auxiliary conductive tube 5, and the auxiliary conductive tube 5 is made of 304 stainless steel; the flexible metal wire 6 is copper wire. By limiting the auxiliary conductive tube 5 to 304 stainless steel and the bevel structure 51 to 5mm, and by using a metal material with excellent conductivity (such as pure copper) for the flexible metal wire 6, stable multi-point electrical contact and mechanical tension transmission under small contact area are achieved, thereby solving the problems of uneven current distribution and localized electric spark ablation caused by poor rigid contact or abrupt changes in conductive cross-sectional area between the electroplating fixture and the micro-optical fiber.

[0021] See Figure 2It should be noted that in some embodiments of the present invention, during the initial low-current electrodeposition, an auxiliary conductive tube 5 made of 304 stainless steel is used to be fitted onto the non-plated section 12. However, when the fiber grating body 1 is subsequently removed from the auxiliary conductive tube 5 for secondary electrodeposition, another tube can still be fitted onto the non-plated section 12. This tube is made of copper, and its end, together with the section to be plated 11 (which is already plated with a nickel metal protective layer 7) and the metal substrate 8, is electroplated in the electroplating solution and then connected and fixed together. Because optical fibers are relatively brittle, fitting a copper tube onto the non-plated section 12 can prevent the optical fiber from being easily broken; moreover, copper has good ductility, allowing for slight bending of the tube (and the corresponding optical fiber) during sensor installation and use to adapt to specific installation application scenarios.

[0022] See Figure 2 and Figure 4 In some embodiments of the present invention, in step S3, the temperature of the initial low-current electrodeposition is controlled at 40–45°C, the deposition time is 480–720 minutes, and the overall diameter of the optical fiber after deposition is 0.5–0.6 mm. By strictly controlling the ambient temperature of the initial low-current electrodeposition at 40–45°C and supplementing it with an ultra-long deposition time of 480–720 minutes, so that the overall diameter of the optical fiber after deposition is 0.5–0.6 mm, the electrochemical reduction kinetics process is deeply and smoothly controlled, so that the grain growth of the nickel metal protective layer 7 reaches the optimal dense state. This solves the problem of large lattice distortion and high residual internal stress in the coating caused by excessively fast electrodeposition rate, which leads to easy generation of microcracks during high-temperature service.

[0023] See Figure 2 and Figure 4 In some embodiments of the present invention, the components of the electroplating solution in steps S3 and S5 include: nickel sulfate hexahydrate at a concentration of 260–280 g / L, nickel chloride hexahydrate at a concentration of 25–35 g / L, boric acid at a concentration of 36–40 g / L, and sodium dodecyl sulfate at a concentration of 0.5–1 g / L. By using a specific concentration of nickel sulfate as the main salt, nickel chloride as the anolyte, boric acid as the buffer, and sodium dodecyl sulfate as the wetting agent to prepare the electroplating solution, efficient and stable transport of nickel ions in the electroplating system, constant pH of the solution, and a significant reduction in cathode surface tension are achieved. This solves the problems of pinholes caused by hydrogen bubbles easily trapped on the coating surface during long-term electrochemical deposition, and the rapid degradation of the plating solution performance.

[0024] See Figure 3In some embodiments of the present invention, in step S4, the heating and curing conditions after applying the resist varnish 9 are as follows: heating at 140–160°C for 20 minutes, followed by natural cooling for 2–6 hours. By setting a gradient curing process of heating at 140–160°C for 20 minutes and then naturally cooling for 2–6 hours, an insulating cured layer with a dense structure, extremely strong adhesion, and no internal stress shrinkage is formed on the surface of the metal substrate 8 by the resist varnish 9. This solves the problems of electroplating solution penetration and abnormal electrodeposition in non-target areas caused by poor curing of the resist varnish, the presence of micropores, or cracking due to rapid temperature changes.

[0025] See Figure 4 In some embodiments of the present invention, in step S5, the deposition time for the secondary embedding electrodeposition is 1440–1680 minutes. By setting the deposition time for the secondary embedding electrodeposition to an ultra-long span of 1440–1680 minutes, a seamless and thorough encapsulation and filling of dense nickel metal from the bottom of the assembly tank 82 upwards is achieved, forming a solid and homogeneous sensor body. This solves the problem that conventional embedded packaging easily leaves tiny cavities between the bottom of the tank and the optical fiber, resulting in unreliable interface bonding and insufficient macroscopic mechanical strength.

[0026] Second aspect See Figure 4 This invention provides a high-temperature resistant fiber Bragg grating sensor with all-metal encapsulation, which is fabricated by the method described in the first aspect. The sensor includes a metal substrate 8 and a metallized fiber Bragg grating 10 embedded and fixed within an assembly groove 82 of the metal substrate 8. The groove edge 83 of the assembly groove 82 and the outer contour edge 81 of the metal substrate 8 are both rounded. A dense nickel metal layer 13 formed by electrodeposition is filled between the metallized fiber Bragg grating 10 and the assembly groove 82. By using a metal substrate 8 with rounded edges 81 and 83, and filling the space between the metallized fiber Bragg grating 10 and the assembly groove 82 with a dense nickel metal layer 13 formed by electrodeposition, a mechanical anchoring of uniform stress distribution in the fiber body and a uniform and smooth transition of electric field distribution on the secondary encapsulation surface are achieved. This not only fundamentally eliminates the tip discharge effect caused by the right-angle geometric abrupt change in traditional substrates, and solves the process defects of abnormal metal accumulation (lumps) on the surface and uneven thickness of the encapsulation layer; at the same time, the dense and non-porous nickel metal filling layer greatly improves the bonding force of heterogeneous interfaces, effectively avoids the accumulation of internal residual stress, solves the technical problem that the sensor is prone to coating cracking and interface peeling in extreme service environments such as high temperature thermal shock or high pressure, and significantly enhances the overall macroscopic mechanical strength and long-term mechanical reliability of the sensor.

[0027] See Figure 4In some embodiments of the present invention, a dense nickel metal layer 13, formed by electrodeposition at a constant current of 0.02–0.03 A, is filled between the metallized fiber grating 10 and the assembly groove 82. By strictly controlling the electrodeposition current of the dense nickel metal layer 13 at an extremely low constant current of 0.02–0.03 A, a deep and gradual control of the electrochemical reduction kinetics process is achieved, further solving the problem that rapid deposition with high current easily leads to the accumulation of high-intensity residual stress inside the filling layer, which in turn easily induces microcracks and interface delamination in the metal layer under high-temperature thermal shock service environments.

[0028] Combination Figure 1 and Figure 4 In some embodiments of the present invention, the radius of curvature of the rounded transition shape is greater than or equal to 0.5 mm. By specifically limiting the radius of curvature of the rounded transition shape at the edge of the metal substrate 8 to greater than or equal to 0.5 mm, the optimal streamlined physical smoothness of the external geometry of the metal substrate 8 is achieved, and the surface charge density in this area is homogenized to the greatest extent. This solves the problem that if only sharp angles or small chamfers are used, there is still a risk of slight electric field enrichment and abnormal local thickness growth.

[0029] See Figure 4 In some embodiments of the present invention, the metallized fiber Bragg grating 10 includes a fiber Bragg grating body 1. The outer surface of the fiber Bragg grating body 1 is sequentially coated with an adhesive layer 2 and a nickel metal conductive layer 3 from the inside out. The adhesive layer 2 is made of titanium or chromium. By intervening between the insulating glass substrate fiber Bragg grating body 1 and the dense nickel metal layer 13 using physical vapor deposition technology, an adhesive layer 2 (the material of the adhesive layer 2 can be titanium or chromium) and a nickel metal conductive layer 3 are added. This achieves a smooth hierarchical transition and atomic-level interlocking from insulator to conductor, and from brittle non-metallic interface to ductile metallic interface. This solves the problem of poor interfacial bonding between heterogeneous materials and interface delamination caused by mismatched thermal expansion coefficients in high-temperature environments, which can easily lead to delamination, caused by relying solely on chemical plating or rough physical friction.

[0030] It is worth noting that the key reason why titanium and chromium can serve as the bonding layer 2 between the fiber grating body 1 and the nickel metal conductive layer 3 is that titanium and chromium are active metals with strong oxygen affinity. During magnetron sputtering, they will capture oxygen atoms from the surface of silicon dioxide (SiO2) and achieve a strong interfacial chemical bond by forming chemical bonds such as Ti-O-Si or Cr-O-Si, rather than simply physical adhesion. At the same time, the titanium and chromium particles formed by sputtering can fill the micro-grooves on the surface of the optical fiber and form a mechanical interlock. Furthermore, the coefficient of thermal expansion and elastic modulus of the bonding layer 2 formed by titanium and chromium are between those of the brittle optical fiber and the subsequent thick nickel layer, which can effectively buffer thermal stress.

[0031] It should be noted that the core advantage of titanium as the adhesive layer 2 lies in its extremely strong chemical reducing properties, which enable it to undergo a full chemical reaction with the surface of the quartz optical fiber, forming a stable Ti-O-Si chemical bonding interface with extremely reliable bonding. Chromium, on the other hand, stands out for its higher deposition rate, more compatible coefficient of thermal expansion with optical fibers, and lower resistivity. These characteristics give it unique advantages in terms of fabrication efficiency, thermal cycling stress buffering, and electroplating current uniformity. Therefore, the aforementioned titanium and chromium adhesive layers 2 offer excellent interfacial bonding reliability, process economy, and thermal compatibility. The choice of titanium or chromium as the specific material for the adhesive layer 2 can be made according to actual application requirements.

[0032] The all-metal packaged high-temperature fiber Bragg grating sensor provided by this invention, with its excellent mechanical reliability and high-temperature resistance, is particularly suitable for parameter measurement and structural health monitoring (SHM) in extreme service environments such as high temperature and high pressure. Specific industrial applications include, but are not limited to: in the field of aero-engines, for real-time strain and temperature monitoring of turbine blades and combustion chamber walls; in the field of heavy-duty gas turbines, for online condition assessment of key hot-end components; and in the nuclear power industry, for long-term online monitoring of core facilities such as pressure vessels and heat exchange tube bundles.

[0033] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. Furthermore, specific examples have been used in the specification to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, and the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for fabricating a high-temperature resistant fiber Bragg grating sensor with all-metal encapsulation, characterized in that, The preparation method includes the following steps: S1. Undercoating: A fiber grating body (1) is provided with a section to be plated (11) along its axial direction and a non-plated section (12) located on at least one side of the section to be plated (11). Physical vapor deposition is performed sequentially on the outer surface of the section to be plated (11) to form an adhesive layer (2) and a nickel metal conductive layer (3), wherein the adhesive layer (2) is titanium metal or chromium metal. S2, Tooling Limiting and Tensioning Assembly: An auxiliary conductive tube (5) with a bevel structure (51) at one end is fitted onto the unplated section (12); the auxiliary conductive tube (5) is held still by the holding structure (141) of the support base (14); one end of a flexible metal wire (6) is physically fixed to the nickel metal conductive layer (3) and electrically conductive, and the other end of the flexible metal wire (6) is connected to the auxiliary conductive tube (5). By bending and shaping the flexible metal wire (6), the fixed auxiliary conductive tube (5) is used as the mechanical force fulcrum, and a tensioning and straightening force is applied along the axial direction of the fiber grating body (1). S3, Initial low-current electrodeposition: The section (11) to be plated of the fiber grating body (1) assembled in step S2 is placed in the electroplating solution, and the auxiliary conductive tube (5) is kept 1-3 mm above the surface of the electroplating solution. Current is conducted through the flexible metal wire (6) and the auxiliary conductive tube (5) to perform electrodeposition under a constant current condition of 0.015-0.03A, forming a dense nickel metal protective layer (7) on the surface of the section (11) to be plated. S4. Substrate anti-discharge and resist plating treatment: A metal substrate (8) with an assembly groove (82) is provided. The outer contour edge (81) of the metal substrate (8) and the groove edge (83) of the assembly groove (82) are rounded to eliminate geometric abrupt changes. The surface of the metal substrate (8) is covered with resist plating paint (9) and heated to cure. Then, a slit (91) is opened in the area corresponding to the assembly groove (82) along the extension direction of the assembly groove (82) to expose part of the inner wall of the assembly groove (82). S5. Secondary embedding electrodeposition: The fiber grating body (1) processed in step S3 is taken out from the auxiliary conductive tube (5) and embedded in the assembly groove (82) of the metal substrate (8) processed in step S4. It is placed in the electroplating solution and subjected to secondary electrodeposition under a constant current of 0.02 to 0.03 A, so that the deposited nickel metal fills the assembly groove (82) and fixes the fiber grating body (1) to the metal substrate (8).

2. The method for fabricating the all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 1, characterized in that: In step S1, physical vapor deposition is performed using magnetron sputtering. When sputtering the adhesive layer (2), the power is set to 100-140W, the pressure to 0.7-1.0Pa, and the sputtering time to 25-35 minutes; When sputtering the nickel metal conductive layer (3), the power is set to 100-140W, the pressure is set to 0.7-1.0Pa, and the sputtering time is 25-35 minutes.

3. The method for fabricating the all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 1, characterized in that: In step S2, the bevel structure (51) is a notch extending 5mm along the axial direction of the auxiliary conductive tube (5), and the material of the auxiliary conductive tube (5) is 304 stainless steel. The flexible metal wire (6) is a copper wire.

4. The method for fabricating the all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 1, characterized in that: In step S3, the temperature of the initial low-current electrodeposition is controlled at 40-45°C, the deposition time is 480-720 minutes, and the overall diameter of the optical fiber after deposition is 0.5-0.6 mm.

5. The method for fabricating the all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 1, characterized in that: In steps S3 and S5, the components of the electroplating solution include: nickel sulfate hexahydrate with a concentration of 260-280 g / L, nickel chloride hexahydrate with a concentration of 25-35 g / L, boric acid with a concentration of 36-40 g / L, and sodium dodecyl sulfate with a concentration of 0.5-1 g / L.

6. The method for fabricating the all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 1, characterized in that: In step S4, the heating and curing conditions after applying the resist paint (9) are: heating at 140-160°C for 20 minutes, followed by natural cooling for 2-6 hours.

7. The method for fabricating the all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 1, characterized in that: In step S5, the deposition time for the secondary embedding electrodeposition is 1440–1680 minutes.

8. A high-temperature resistant fiber Bragg grating sensor with all-metal encapsulation, characterized in that: The sensor is prepared by the preparation method described in any one of claims 1 to 7; The sensor includes a metal substrate (8) and a metallized fiber optic grating (10) embedded in and fixed in the mounting groove (82) of the metal substrate (8). The groove edge (83) of the assembly groove (82) and the outer contour edge (81) of the metal substrate (8) are both rounded; a dense nickel metal layer (13) formed by electrodeposition is filled between the metallized fiber grating (10) and the assembly groove (82).

9. The all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 8, characterized in that: The radius of curvature of the rounded transition shape is greater than or equal to 0.5 mm.

10. The all-metal packaged high-temperature resistant fiber Bragg grating sensor as described in claim 8, characterized in that: The metallized fiber grating (10) includes a fiber grating body (1), and the outer surface of the fiber grating body (1) is covered with an adhesive layer (2) and a nickel metal conductive layer (3) from the inside to the outside. The adhesive layer (2) is titanium metal or chromium metal.

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