Arrayed fiber Bragg grating strain gauge, mold and method for preparing arrayed fiber Bragg grating strain gauge

Abstract

The present invention relates to the field of optical fiber sensor technology, and discloses an arrayed fiber Bragg grating strain gauge, a mold for preparing the arrayed fiber Bragg grating strain gauge, and a method for preparing the arrayed fiber Bragg grating strain gauge. The arrayed fiber Bragg grating strain gauge comprises an optical fiber, on which a temperature compensation accessory and a plurality of strain measurement accessories are provided; the strain measurement accessory is used to measure strain; and the temperature compensation accessory isolates strain and serves as temperature compensation. The present invention combines the advantages of a grating optical fiber sensor with an electronic strain gauge to produce an arrayed fiber Bragg grating strain gauge. This combines the high sensitivity and multi-point monitoring capabilities of a grating optical fiber with the mechanical protection and waterproof and anti-corrosion properties of an electronic strain gauge, while simultaneously solving the decoupling problem between temperature and strain and improving the stability and durability of the fiber Bragg grating strain gauge.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensors, and in particular to an arrayed optical fiber Bragg grating strain gauge, a mold for preparing the arrayed optical fiber Bragg grating strain gauge, and a method for preparing the arrayed optical fiber Bragg grating strain gauge. Background Art

[0002] Fiber Bragg grating (FBG) strain gauges are sensors based on the periodic structure within optical fibers, enabling highly sensitive, real-time monitoring of parameters such as strain and temperature. Compared to traditional sensors like resistance strain gauges and strain gauges, FBG sensors offer advantages such as small size, light weight, strong interference resistance, and ease of remote monitoring. Arrayed FBG sensors also enable high-capacity multiplexing and simultaneous multi-point monitoring, making them extremely valuable in engineering and science.

[0003] However, in practical engineering applications, the packaging and protection of fiber Bragg grating sensors remains a challenge that needs to be addressed. In engineering environments, fiber Bragg grating sensors must possess excellent mechanical protection, waterproof and corrosion resistance, and high-temperature resistance to ensure their stability and reliability under extreme conditions.

[0004] Currently, fiber Bragg grating (FBG) packaging technologies primarily focus on fixing and protecting the grating. Traditional packaging methods primarily utilize organic adhesives, with epoxy adhesives being the most common. However, this adhesive packaging method is subject to long-term creep, aging, and performance degradation in high-temperature environments. Furthermore, parameters such as the length and thickness of the FBG adhesive affect the FBG's sensitivity to temperature and strain, making it difficult to ensure consistent sensitivity after packaging. Another packaging method involves metallization of the grating surface. This process deposits a metal coating on the grating surface through methods such as electroless plating, chemical vapor deposition, plasma deposition, and magnetron sputtering, and then secures the grating to the metal test piece through welding. However, while metallization eliminates the need for adhesives, it still presents the following challenges: First, the metal film formed may contain microscopic defects, pores, and particles, which can cause uneven stress on the FBG and potentially waveform deformation. Second, localized high temperatures at the weld point can lead to uneven weld stress distribution, compromising performance. Third, the metal film is susceptible to corrosion from air and acids and alkalis, making it difficult to effectively protect the FBG over the long term. Summary of the Invention

[0005] The present invention aims to overcome the problems of traditional grating fiber packaging methods and provide an arrayed fiber Bragg grating strain gauge, a mold for preparing the arrayed fiber Bragg grating strain gauge, and a method for preparing the arrayed fiber Bragg grating strain gauge. This method combines the advantages of grating fiber sensors and electronic strain gauges to produce an arrayed fiber Bragg grating strain gauge. It combines the high sensitivity and multi-point monitoring capabilities of grating fibers with the mechanical protection and waterproof and anti-corrosion properties of electronic strain gauges, while solving the decoupling problem between temperature and strain and improving the stability and durability of the fiber Bragg grating strain gauge.

[0006] In order to achieve the above-mentioned object, the present invention provides an arrayed fiber Bragg grating strain gauge, wherein the arrayed fiber Bragg grating strain gauge includes an optical fiber, and a temperature compensation accessory and a plurality of strain measurement accessories are provided on the optical fiber;

[0007] The strain measurement accessory is used to measure strain; the temperature compensation accessory isolates strain and is used for temperature compensation.

[0008] A second aspect of the present invention provides a mold for preparing the above-mentioned arrayed fiber Bragg grating strain gauge, wherein the mold includes a plurality of template blocks and a fixture;

[0009] A rectangular slot running through the template block is provided on the top of each template block;

[0010] The clamp is used to clamp several template blocks at the same time.

[0011] A third aspect of the present invention provides a method for preparing an arrayed fiber Bragg grating strain gauge using the above mold, the method comprising the following steps:

[0012] A clamp is used to simultaneously clamp several template blocks, polyamic acid is applied to the surface of the substrate, and then the substrate coated with polyamic acid is placed in the rectangular groove of each template block. An optical fiber is placed in the rectangular groove of the template block so that the optical fiber grating is located in the rectangular groove. Polyamic acid is dripped into the gap in the rectangular groove so that the polyamic acid wraps around the optical fiber located in the rectangular groove. Then, a heat shrink polymerization reaction is performed to obtain a semi-finished array fiber Bragg grating strain gauge.

[0013] Adhesive is applied on the surface of the polyimide package block to form an adhesive layer, a glass fiber cover plate is covered on the adhesive layer, a capillary is sheathed on the outside of the remaining gratings, and both ends are sealed with glue to obtain an arrayed fiber Bragg grating strain gauge.

[0014] Beneficial effects of the present invention:

[0015] 1. The use of molds can effectively control variables, facilitate the consistency of packaging and enable batch production.

[0016] 2. The use of tight-packed optical fiber for packaging significantly improves the bending and tensile properties of the non-grid part. The non-glue packaging of the grid area does not have the problem of uneven stress and can effectively protect and bond the optical fiber sensor.

[0017] 3. Using another grating on the same optical fiber as a temperature compensation grating maintains the advantages of splicing connection and reduces the occupation of signal channels. A single optical fiber can achieve accurate measurement of strain. At the same time, the arrayed fiber Bragg grating strain gauge can achieve large-capacity multiplexing and simultaneous multi-point monitoring.

[0018] 4. Reduced installation costs and time, no need for special optical tools or professional technicians.

[0019] 5. It solves the problems faced by fiber Bragg grating packaging, such as complex operation, inability to withstand high and low temperatures, and inability to achieve temperature and strain decoupling. It also solves the problem that fiber Bragg grating strain gauges cannot measure at multiple points and cannot be adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 1 is a schematic diagram of the top view of the arrayed fiber Bragg grating strain gauge of the present invention;

[0021] Figure 2 is a schematic diagram of an arrayed fiber Bragg grating strain gauge of the present invention;

[0022] Figure 3 is a schematic cross-sectional view of a strain measurement accessory of an arrayed fiber Bragg grating strain gauge of the present invention;

[0023] Figure 4 It is a structural schematic diagram of the template block of the present invention;

[0024] Figure 5 It is a schematic structural diagram of the clamp of the present invention;

[0025] Figure 6 The present invention is a flowchart of a method for preparing an arrayed fiber grating strain gauge using the mold of the present invention.

[0026] Description of Reference Numerals

[0027] 1. Optical fiber; 11. Grating; 2. Temperature compensation accessories; 3. Strain measurement accessories;

[0028] 31. Substrate; 311. Adhesive layer; 32. Polyimide encapsulation block; 33. Fiberglass cover; 331. Adhesive layer;

[0029] 4. Template block; 41. Rectangular slot; 5. Clamp; 51. First clamp; 52. Second clamp; 53. Back plate; 54. Screw. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0031] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0032] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0033] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments provided by the present invention can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0034] The present invention will be described in detail below through examples.

[0035] Example 1

[0036] like Figure 1 and Figure 2 The arrayed fiber Bragg grating strain gauge ( Figure 1 This is a top view of the arrayed fiber Bragg grating strain gauge. Figure 2 Schematic diagram of an arrayed fiber Bragg grating strain gauge). The arrayed fiber Bragg grating strain gauge includes an optical fiber 1 (the optical fiber 1 used in the present invention is a tight-wrapped optical fiber prepared by a fiber tight-wrapping machine. The use of a tight-wrapped optical fiber can enhance the bending and tensile properties of the non-braided area). A temperature compensation accessory 2 and several strain measurement accessories 3 are provided on the optical fiber 1.

[0037] The strain measurement accessory 3 is used to measure strain; the temperature compensation accessory 2 isolates strain and is used for temperature compensation.

[0038] In the arrayed fiber Bragg grating strain gauge of the present invention, the number of gratings 11 on the optical fiber 1 is at least three, the number of temperature compensation accessories 2 is one, and the number of strain measurement accessories 3 is at least two (the number of strain measurement accessories 3 is related to the number of gratings 11, that is, one grating 11 on the optical fiber 1 is provided with a temperature compensation accessory 2, and the remaining gratings 11 are each provided with a corresponding strain measurement accessory 3; for example, when there are five gratings 11 on the optical fiber 1, one temperature compensation accessory 2 and four strain measurement accessories 3 are provided on the optical fiber 1; when there are three gratings 11 on the optical fiber 1, one temperature compensation accessory 2 and two strain measurement accessories 3 are provided on the optical fiber 1).

[0039] In the present invention, the temperature compensation accessory 2 is a capillary tube sleeved on the outside of the optical fiber 1 , and is further a stainless steel capillary tube, and the sleeved optical fiber 1 is provided with a grating 11 .

[0040] The length of the capillary is greater than or equal to twice the length of the grating 11 set in the capillary; and the inner diameter of the capillary is 0.15-0.25 mm, and the outer diameter is 0.4-0.6 mm.

[0041] Furthermore, in this embodiment, the length of the capillary is twice the length of the grating 11 sleeved in the capillary; and the inner diameter of the capillary is 0.2 mm, and the outer diameter is 0.5 mm.

[0042] In the present invention, the grating 11 is affected by temperature and strain during measurement, both of which can cause wavelength changes. The capillary-encapsulated grating 11 is not affected by strain changes (the strain measurement accessory 3 is attached to the surface of the object being measured when measuring strain, and the temperature compensation accessory 2 does not need to be attached and fixed to the surface of the object being measured and is not affected by strain itself). It is only affected by temperature. In this way, the error in the wavelength change caused by temperature in the remaining grating 11 used to measure strain can be eliminated, making the result more accurate.

[0043] In the present invention, the cross section of the strain measurement accessory 3 is as follows: Figure 3 As shown, each strain measurement accessory 3 includes a substrate 31 and an adhesive layer 311 provided on the upper surface of the substrate 31. A polyimide encapsulation block 32 is provided on the upper surface of the adhesive layer 311. The polyimide encapsulation block 32 completely covers the upper surface of the adhesive layer 311. The polyimide encapsulation block 32 is wrapped around the outside of the optical fiber 1, and the wrapped optical fiber 1 is provided with a grating 11. An adhesive layer 331 is provided on the upper surface of the polyimide encapsulation block 32, and a glass fiber cover 33 is also covered on the upper surface of the adhesive layer 331.

[0044] The strain measurement accessory 3 of the present invention is generally in the shape of a rectangular parallelepiped, and its specific size is related to the size required in actual use. The thickness of the substrate 31 is determined according to the transfer coefficient required by the specifically prepared arrayed fiber Bragg grating strain gauge.

[0045] In the present invention, the material of the substrate 31 is selected from aluminum, aluminum alloy, stainless steel, copper or polyimide, and in this embodiment, is further polyimide.

[0046] Because the elastic modulus of the material of the substrate 31 affects the strain transfer coefficient, that is, the adequacy of the strain transfer of the measured object, when the shear modulus of the material of the substrate 31 is less than 400 MPa, a small change in the shear modulus will have a significant impact on the strain transfer coefficient. Therefore, different materials are selected here. On the one hand, this avoids the influence of the shear modulus on strain transfer. On the other hand, different materials can be used to prepare arrayed fiber grating strain gauges with different strain transfer coefficients to meet the sensitivity requirements under different working conditions. Therefore, in terms of material selection, materials with a large shear modulus are selected. The thickness of the substrate 31 will affect the strain transfer coefficient. The thicker the substrate 31, the less sufficient the strain transfer. The thinner the material that meets the requirements, the higher the production cost. Therefore, while meeting different working conditions, a substrate 31 of appropriate thickness can be selected.

[0047] In the present invention, the bonding layer 311 and the polyimide encapsulation block 32 are both obtained by curing polyamic acid through a heat shrinkage polymerization reaction; the adhesive layer 331 is formed by applying adhesive on the upper surface of the polyimide encapsulation block 32 .

[0048] Example 2

[0049] like Figure 4 and 5 The mold for preparing the arrayed fiber Bragg grating strain gauge of Example 1 shown in FIG. 1 includes several Figure 4 The template block 4 shown and Figure 5 The clamp 5 shown;

[0050] A rectangular slot 41 is formed on the top of each template block 4 and passes through the template block 4 (the template block 4 is made of glass);

[0051] The clamp 5 is used to clamp several template blocks 4 at the same time.

[0052] In the present invention, the length of the rectangular groove 41 is along the axial direction of the rectangular groove 41. The specific size of the rectangular groove 41 is related to the size of the prepared strain measurement accessory 3, wherein the length and width of the rectangular groove 41 are the same as the length and width of the strain measurement accessory 3 of the fiber Bragg grating strain gauge finally obtained, and the depth of the rectangular groove 41 is equal to the sum of the thickness of the substrate 31 and the diameter of the optical fiber (the diameter of the optical fiber is generally 125um).

[0053] Furthermore, in the present invention, the clamp 5 simultaneously clamps one side of the rectangular groove 41 of each template block 4 (there is no special requirement for the specific clamping position, as long as it can clamp one side of the rectangular groove 41 of several template blocks 4 at the same time and clamp and fix several template blocks 4).

[0054] In the present invention, the clamp 5 includes a first clamping plate 51 , a second clamping plate 52 and a back plate 53 connecting the first clamping plate 51 and the second clamping plate 52 .

[0055] In the present invention, the clamp 5 further includes a screw 54 (the screw 54 passes through the first clamping plate 51 and the second clamping plate 52 ), and the distance between the first clamping plate 51 and the second clamping plate 52 is controlled by adjusting the screw 54 to achieve clamping of the template block 4 .

[0056] Furthermore, one side of the first clamping plate 51 and the second clamping plate 52 are connected by a back plate 53 , and the other sides are controlled by screws 54 to be able to approach each other to form a clamping gap to clamp the template block 4 .

[0057] During actual use, the clamp 5 needs to clamp multiple template blocks 4 at the same time (the number of template blocks 4 used in actual use is the same as the number of strain measurement accessories 3 finally obtained), so the clamp length of the clamp 5 (the clamp length of the clamp 5 is the same as the length of the first clamp 51 and the second clamp 52) needs to be greater than or equal to twice the length of the template block 4.

[0058] Example 3

[0059] like Figure 6 The method for preparing an arrayed fiber Bragg grating strain gauge using the mold of Example 2 includes the following steps:

[0060] (1) Use the clamp 5 to clamp several template blocks 4 at the same time (adjust the screw 54 to control the distance between the first clamping plate 51 and the second clamping plate 52 so that a clamping opening is formed between the first clamping plate 51 and the second clamping plate 52 and the several template blocks 4 are clamped and fixed at the same time; the number of template blocks 4 used is the same as the number of strain measurement accessories 3 to be set, and the spacing between the template blocks 4 is adjusted according to the spacing between the gratings 11 on the optical fiber 1), apply polyamic acid on the surface of the substrate 31, and then place the substrate 31 with the surface coated with polyamic acid in the rectangular groove 41 of each template block 4 (the substrate 31 is a rectangular parallelepiped, and the length of the substrate 31 is equal to the length of the rectangular groove 41, The width of the substrate 31 is equal to the width of the rectangular groove 41 ), and the optical fiber 1 is placed in the rectangular groove 41 of each template block 4, so that all gratings 11 on the optical fiber 1 except for one grating 11 (this grating 11 is used to mount the temperature compensation accessory 2) are located in their respective rectangular grooves 41 (one grating 11 corresponds to each rectangular groove 41; the spacing between the template blocks 4 is adjusted according to the spacing between the gratings 11 placed in the rectangular grooves 41). Polyamic acid is dripped into the gaps in the rectangular grooves 41 so that the polyamic acid wraps around the optical fiber 1 located in the rectangular grooves 41, and then a heat shrink polymerization reaction is carried out. After the heat shrink polymerization reaction is completed, a semi-finished fiber grating strain gauge array is obtained;

[0061] (2) The arrayed fiber Bragg grating strain gauge semi-finished product is separated from the rectangular groove 41, and adhesive is applied on the surface of the polyimide packaging block 32 to form an adhesive layer 331. The adhesive layer 331 is covered with a glass fiber cover plate 33. Then, a capillary is set on the outer side of the remaining grating 11 without the strain measurement accessory 3, and the two ends are sealed with glue to obtain an arrayed fiber Bragg grating strain gauge.

[0062] Furthermore, in step (1) of the present invention, the purpose of applying polyamic acid on the surface of the substrate 31 is to degrease and roughen the surface of the substrate 31 (degreasing is to remove grease, dust, sweat and other substances on the surface of the substrate 31, and roughening makes the surface of the substrate 31 microscopically rough, which can ensure that the subsequently dropped polyamic acid has good bonding with the surface of the substrate 31) to ensure good wettability and adhesion. At the same time, after the subsequent heat shrinkage polymerization reaction, the polyamic acid on the surface of the substrate 31 will solidify, forming a corresponding bonding layer 311 on the surface of the substrate 31 (the material of the bonding layer 311 is polyimide), which further plays a bonding role.

[0063] In the present invention, the amount of polyamic acid applied to the surface of the substrate 31 only needs to be sufficient to remove oil, roughen and bond the substrate. Therefore, the depth of the rectangular groove 41 in the present invention is equal to the sum of the diameter of the optical fiber 1, the thickness of the substrate 31 and the thickness of the bonding layer 311. However, in actual operation, the amount of polyamic acid applied to the surface of the substrate 31 is relatively small, so the thickness of the bonding layer 331 can be ignored.

[0064] In the present invention, the optical fiber 1 is placed in the rectangular groove 41, and the two ends of the optical fiber 1 are fixed in sequence with high-temperature polyimide tape. At the same time, the corresponding grating 11 on the optical fiber 1 (the grating 11 is written in sequence using an excimer laser and a phase mask. The optical fiber is placed behind the phase mask (the fiber stripping part is opposite the phase mask). The excimer laser is used to emit laser light. The laser passes through the beam expander and the focusing lens and irradiates the phase mask. After passing through the phase mask, a diffraction beam is formed and irradiates the optical fiber core. The hydrogen molecules in the irradiated part of the core immediately react chemically with germanium to form Ge-OH bonds and Ge-H bonds, thereby permanently increasing the refractive index of this part. The above steps are the grating writing process) is located in the rectangular groove 41 (the coating layer and the tight cladding at the grating 11 are stripped off, which can reduce the transfer layer and make the measurement results more accurate).

[0065] Furthermore, the length of the rectangular groove 41 in the present invention is 2-3 times the length of the grating 11 encapsulated in the polyimide packaging block 32. In this embodiment, the length of the rectangular groove 41 is twice the length of the grating 11 encapsulated in the polyimide packaging block 32, and the grating 11 is located in the middle of the rectangular groove 41.

[0066] In the present invention, after the grating 11 is placed in the rectangular groove 41, polyamic acid is dripped into the gap in the rectangular groove 41. The dripped polyamic acid fills the gap in the rectangular groove 41 and wraps the optical fiber 1 located at the rectangular groove 41 (polyamic acid has low fluidity and is a viscous liquid at room temperature with a certain surface tension, so it can completely fill the gap in the rectangular groove 41). Then, it is placed in a hot oven for a thermal shrinkage polymerization reaction (including two processes of dehydration and imidization). The conditions for the thermal shrinkage polymerization reaction include: keeping warm at 80-100°C for 0.5-1.5h, then heating to 150-200°C for keeping warm for 0.5-1.5h, and finally heating to 200-220°C for keeping warm for 1-3h; in this embodiment, the conditions for the thermal shrinkage polymerization reaction include: keeping warm at 100°C for 1h, then heating to 160°C for keeping warm for 1h, and finally heating to 220°C for keeping warm for 2h.

[0067] After the heat shrinkage polymerization reaction is completed in the present invention, the hot oven is turned off and allowed to cool naturally. When the temperature drops to 150°C, the mold is removed, the polyimide high-temperature tape is peeled off, and the rectangular groove 41 and the array fiber grating strain gauge semi-finished product are separated using a utility knife (at this time, the polyamic acid filled in the gap of the rectangular groove 41 undergoes a heat shrinkage polymerization reaction and solidifies to form a polyimide encapsulation block 32. The length of the polyimide encapsulation block 32 is equal to the length of the rectangular groove 41, the height is equal to the diameter of the optical fiber 1, and the width is equal to the width of the rectangular groove 41; at the same time, the polyamic acid applied to the surface of the substrate 31 is solidified to form a corresponding adhesive layer 311 on the upper surface of the substrate 31).

[0068] In the present invention, a semi-finished fiber Bragg grating strain gauge array is obtained, and adhesive is applied to the upper surface of a polyimide packaging block 32 to form an adhesive layer 31. Then, a glass fiber cover plate 33 is covered on the upper surface of the adhesive layer 31. Then, a capillary is sheathed on the outer side of the remaining grating 11 without a strain measurement accessory 3, and both ends of the capillary are sealed with glue to finally obtain an array fiber Bragg grating strain gauge.

[0069] Furthermore, the amount of glue (the glue is a conventional adhesive type glue, further, the glue is selected from epoxy resin glue and / or UV curing glue, in this embodiment, the glue is selected from UV curing glue) is sufficient to form an adhesive layer 31 to stick the fiberglass cover 33, further, the length of the fiberglass cover 33 is equal to the length of the rectangular groove 41, and the width of the fiberglass cover 33 is equal to the width of the rectangular groove 41.

[0070] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0071] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. An arrayed fiber Bragg grating strain gauge, characterized in that: The arrayed fiber grating strain gauge comprises an optical fiber (1), and a temperature compensation accessory (2) and a plurality of strain measurement accessories (3) are provided on the optical fiber (1); The strain measurement accessory (3) is used to measure strain; the temperature compensation accessory (2) isolates strain and is used for temperature compensation; Each strain measurement accessory (3) comprises a substrate (31) and an adhesive layer (311) arranged on the upper surface of the substrate (31); a polyimide encapsulation block (32) is arranged on the upper surface of the adhesive layer (311); the polyimide encapsulation block (32) completely covers the upper surface of the adhesive layer (311); the polyimide encapsulation block (32) is wrapped around the outer side of the optical fiber (1), and the wrapped optical fiber (1) is provided with a grating (11); an adhesive layer (331) is arranged on the upper surface of the polyimide encapsulation block (32), and a glass fiber cover plate (33) is also covered on the upper surface of the adhesive layer (331).

2. The arrayed fiber Bragg grating strain gauge according to claim 1, wherein: The temperature compensation accessory (2) is a capillary tube sleeved on the outside of the optical fiber (1), and the sleeved optical fiber (1) is provided with a grating (11); The length of the capillary is greater than or equal to twice the length of the grating (11); The inner diameter of the capillary is 0.15-0.25 mm, and the outer diameter is 0.4-0.6 mm.

3. The arrayed fiber Bragg grating strain gauge according to claim 1 or 2, characterized in that: The material of the substrate (31) is selected from aluminum, aluminum alloy, stainless steel, copper or polyimide.

4. A mold for preparing the arrayed fiber Bragg grating strain gauge according to any one of claims 1 to 3, characterized in that: The mold includes a plurality of template blocks (4) and a clamp (5); A rectangular groove (41) is provided on the top of each template block (4) and passes through the template block (4); The clamp (5) is used to clamp a plurality of template blocks (4) at the same time.

5. The mold for preparing an arrayed fiber Bragg grating strain gauge according to claim 4, wherein: The clamp (5) simultaneously clamps one side of the rectangular slot (41) of each template block (4).

6. The mold for preparing an arrayed fiber Bragg grating strain gauge according to claim 4 or 5, characterized in that: The clamp (5) comprises a first clamping plate (51), a second clamping plate (52), and a back plate (53) connecting the first clamping plate (51) and the second clamping plate (52); The clamp (5) further comprises a screw (54), and the distance between the first clamping plate (51) and the second clamping plate (52) is controlled by the screw (54) to achieve clamping of the template block (4).

7. The mold for preparing an arrayed fiber Bragg grating strain gauge according to claim 6, wherein: The clamping length of the clamp (5) is greater than or equal to twice the length of the template block (4).

8. A method for preparing an arrayed fiber Bragg grating strain gauge using the mold according to any one of claims 4 to 7, characterized in that: The method comprises the following steps: A clamp (5) is used to simultaneously clamp a plurality of template blocks (4), polyamic acid is applied to the surface of the substrate (31), and then the substrate (31) with the polyamic acid applied to the surface is placed in the rectangular groove (41) of each template block (4), and the optical fiber (1) is placed in the rectangular groove (41) of the template block (4), and the grating (11) of the optical fiber (1) is located in the rectangular groove (41), and polyamic acid is dripped into the gap in the rectangular groove (41), and the polyamic acid is wrapped around the optical fiber (1) located in the rectangular groove (41), and then a heat shrinkage polymerization reaction is performed to obtain a semi-finished product of an arrayed optical fiber Bragg grating strain gauge; Viscose is applied on the surface of the polyimide packaging block (32) to form an adhesive layer (331), a glass fiber cover plate (33) is covered on the adhesive layer (331), a capillary is sheathed on the outer side of the remaining gratings (11), and both ends are sealed with glue to obtain an array-type fiber Bragg grating strain gauge.

9. The method for preparing an arrayed fiber Bragg grating strain gauge using a mold according to claim 8, wherein: The length of the rectangular groove (41) is 2-3 times the length of the grating (11).

10. The method for preparing an arrayed fiber Bragg grating strain gauge using a mold according to claim 8 or 9, wherein: The conditions of the thermal shrinkage polymerization reaction include: keeping the temperature at 80-100° C. for 0.5-1.5 hours, then heating to 150-200° C. for 0.5-1.5 hours, and finally heating to 200-220° C. for 1-3 hours.

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