Transient displacement sensor based on uniform macro-bending loss of optical fiber and dynamic change of transient displacement sensor based on elastic substrate tension and compression, manufacturing method and application thereof

Abstract

This invention provides a transient displacement sensor based on uniform macro-bending loss of optical fiber and dynamic changes in tension and compression of an elastic substrate, along with its fabrication method and applications, belonging to the field of optical fiber sensor design. It includes an elastic substrate and an optical fiber inserted into the elastic substrate. The optical fiber is inserted into the elastic substrate at equal intervals and fixedly connected to the substrate at the insertion points. After insertion, the optical fiber exhibits a continuous wavy bend with identical shapes. One end of the optical fiber is connected to a light source, and the other end is connected to a photodiode. Deformation of the elastic substrate along the length of the optical fiber causes a change in the fiber's curvature. The width of the elastic substrate is 20-500 times the diameter of the optical fiber. The sensor fabrication method is simple, convenient, reliable, and easy to operate. The sensor measures a wider displacement range, can perform continuous measurements, and has a larger dynamic monitoring range. In application, this invention exhibits a large linear region and high reliability.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensor design, specifically relating to a transient displacement sensor based on the uniform macrobending loss of optical fiber and the dynamic changes in tension and compression of an elastic substrate, as well as its fabrication method and application. Background Technology

[0002] Optical fiber, also known as optical waveguide fiber, is a fiber material made of glass or plastic that transmits light using the principle of total internal reflection. Because optical fibers have a relatively small diameter, they are easily bent during use. When the curvature of the bent section of the fiber is sufficiently large, the light transmission path changes, with many transmission modes being converted into radiation modes. This light enters the cladding and is absorbed by the coating layer; that is, some light leaks at the bend, a phenomenon known as macro-bending loss. In communication optical fibers, macro-bending loss caused by route bends and laying curves is generally considered a negative factor because it is not a sensitive factor in optical fiber communication; lower loss is better. However, if this macro-bending loss is properly predicted and utilized, macro-bending sensors can be fabricated.

[0003] Fiber optic sensors have become an important method for structural health monitoring in the aerospace and automotive industries. The method of replacing glass fibers or fiber bundles in fiber-reinforced composite panels or pipes with optical fibers has high application potential. Fiber optic sensors are lightweight, small in size, and highly sensitive; however, conventional fiber optic sensing methods struggle to monitor large displacements. Furthermore, existing macro-bending fiber optic sensors suffer from problems such as discontinuous displacement sensing, unstable and variable fiber macro-bending rates, and difficulty in accurately controlling the fiber macro-bending rate.

[0004] The patent with publication number CN114993187A employs a method of embedding the bent portion of the optical fiber entirely into an elastic substrate to achieve macro-bending. The contraction deformation of the elastic substrate is influenced by the deformation of the optical fiber, and the deformations of the two are coordinated. However, due to the large contact area, and influenced by boundary conditions, the deformation at the edge of the elastic substrate differs significantly from that at the center. The deformation of the optical fiber in the center is large, while the deformation of the optical fiber at the edge gradually decreases, and the rate of decrease is uncontrollable and nonlinear. Furthermore, stress mismatch can lead to instability, and the resulting wavy optical fiber is limited by the complete contact bonding method, resulting in significant differences in the shape of each wave. This randomness of variation makes the macro-bending rate uncontrollable, making it impossible to obtain a sensor with the target measurement range through curvature design.

[0005] Compared to the aforementioned existing patents, where the optical fiber is entirely arranged on the surface of an elastic substrate and fixed to the substrate only with adhesive, if the longitudinal width of the elastic substrate is not designed to reach a certain length, the sensor after prestress relaxation may experience torsion or other complex deformations, failing to achieve the desired flatness. This requires the width of the elastic substrate to be much larger than the diameter of the optical fiber, significantly increasing the unnecessary mass of the sensor and the load on the measured surface. Besides increasing measurement errors, this also eliminates the possibility of measuring the vibration of minute structures. Furthermore, when using the optical fiber sensor in the aforementioned patents, it is impossible to achieve single-point displacement measurement of the surface of the measured structure because the deformation of the optical fiber relies on the clamping and stretching of the two short sides of the elastic substrate. In practical applications, one short side needs to be completely adhered to the measured surface, and the measurement range is the coupling of displacements at countless points along this short side, which is of little practical significance and cannot accurately obtain the displacement measurement result of a single point. Summary of the Invention

[0006] To address the problems in the prior art, this invention proposes a transient displacement sensor based on the uniform macrobending loss of optical fiber and the dynamic changes in tension and compression of an elastic substrate, as well as its fabrication method and application.

[0007] The technical solution adopted in this invention is as follows:

[0008] In a first aspect, the present invention discloses a transient displacement sensor based on uniform macrobending loss of optical fiber and dynamic changes in tension and compression of an elastic substrate, comprising an elastic substrate and an optical fiber inserted into the elastic substrate; the optical fiber is inserted into the elastic substrate at the same spacing and is fixedly connected to the elastic substrate at the insertion point, and the optical fiber exhibits continuous wavy bending after insertion, and the bending shape is completely identical; one end of the optical fiber is connected to a light source and the other end is connected to a photodiode; when the elastic substrate deforms in the length direction of the optical fiber, it will cause the optical fiber to undergo a change in bending curvature; the width of the elastic substrate is 20-500 times the diameter of the optical fiber.

[0009] Secondly, the present invention discloses a method for manufacturing the aforementioned transient displacement sensor, comprising the following steps:

[0010] 1) Insert optical fibers at the same spacing onto the elastic substrate, wherein the length direction of the optical fibers is consistent with the length direction of the elastic substrate; and use the length direction of the elastic substrate as the direction for subsequent pre-stretching;

[0011] 2) The elastic substrate is stretched to its maximum elongation ratio. Under the stretched state, the optical fiber is straightened and attached to the upper and lower surfaces of the elastic substrate. The optical fiber and the elastic substrate are fixed at the current insertion position of the optical fiber and the elastic substrate.

[0012] 3) Remove the stretching of the elastic substrate. The optical fiber that was originally attached to the elastic substrate bends into the same arch shape as the elastic substrate shrinks. The optical fiber as a whole shrinks into a wave shape. Connect one end of the optical fiber to the light source and the other end to the photodiode to obtain the transient displacement sensor.

[0013] Thirdly, the present invention discloses a method for displacement measurement using the aforementioned transient displacement sensor, comprising the following steps:

[0014] The elastic substrate is pre-stretched along the length of the optical fiber, and the elongation ratio of the elastic substrate during pre-stretching is less than the maximum elongation ratio of the elastic substrate. Then, one end of the long side of the elastic substrate in the pre-stretched state is vertically fixed to the surface of the structure to be tested, and the other end is vertically fixed to the surface of any fixed structure. One end of the optical fiber is connected to a light source, and the other end is connected to a photodiode.

[0015] The displacement signal of the structure under test in the direction of the fiber arrangement will be transformed into the curvature change of the fiber bending. The curvature change of the fiber bending will eventually change the optical power signal received by the photodiode. The photodiode converts the optical power signal into an electrical signal output, that is, the transient displacement change of the surface of the structure under test is obtained.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) Compared with traditional fiber Bragg grating sensors, the present invention can measure a larger displacement range.

[0018] (2) Compared with existing fiber macrobend sensors, the fiber sensor of the present invention can continuously measure the out-of-plane displacement of the structure under test, and its dynamic monitoring range is larger than that of traditional fiber macrobend sensors. Furthermore, the present invention improves the existing line bonding method to point bonding, which minimizes the contact area between the fiber and the elastic substrate. The size of the macrobend ring of the fiber is determined by the distance between the two arch feet, which can accurately control the shape of the macrobend ring and thus determine the curvature. By perforating the prestressed elastic substrate and point bonding it with the fiber, the bending curvature of the fiber can be well maintained in a uniform, regular and repeatable state, which further expands the application scope of this type of macrobend fiber sensor and can be applied to the large-scale transient displacement measurement of microstructures.

[0019] (3) This invention uses multiple macro-arches to simultaneously pull and compress to measure transient displacement, resulting in a large linear region and high reliability. The width of the elastic substrate in this invention is 20-500 times the diameter of the optical fiber. If the width of the elastic substrate is less than 20 times the diameter of the optical fiber, the width of the elastic substrate is too small and cannot be stably fixed. If the width of the elastic substrate is greater than 500 times the diameter of the optical fiber, the width of the elastic substrate is too wide, the short side width is too large, which increases the load and loses the possibility of measuring single-point displacement. The instantaneous displacement sensor of this invention can fix one end of the elastic substrate to the surface of the object to be measured and attach a circle with a diameter of 3mm. By adjusting the orientation of the elastic substrate in the direction of the optical fiber, the motion of the measured system in a selected direction at a selected point can be collected.

[0020] (4) Compared with traditional fiber macrobend sensors, the present invention has a simple bonding method, convenient manufacturing process, high reliability and easy operation. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the one-dimensional displacement sensor of the present invention;

[0022] Figure 2 This is a flowchart illustrating the fabrication process of the one-dimensional displacement sensor of the present invention.

[0023] Figure 3 This is a diagram of the linear region verification experiment for the one-dimensional displacement sensor of this invention;

[0024] Figure 4 for Figure 3 oscilloscope for signal measurement;

[0025] Figure 5 This is a setup diagram of an application example of the one-dimensional displacement sensor of the present invention;

[0026] Figure 6 for Figure 5 A comparison diagram of oscilloscope measurement signals and reliable Doppler vibration meter signals in a sensing example;

[0027] Figure 7 This is a flowchart illustrating the design scheme of the one-dimensional displacement sensor of the present invention. Detailed Implementation

[0028] The present invention will be further described and illustrated below with reference to specific embodiments. The embodiments described are merely examples of the content of this disclosure and do not limit the scope of the invention. The technical features of each embodiment in the present invention can be combined accordingly, provided that there is no mutual conflict.

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0031] In addition, in the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] The present invention will be further described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 The diagram shows a schematic of the fiber macrobending loss one-dimensional displacement sensor of the present invention. The present invention discloses a transient displacement sensor based on uniform macrobending loss of an optical fiber and dynamic changes in the tension and compression of an elastic substrate. It includes an elastic substrate and an optical fiber inserted into the elastic substrate. The optical fiber is inserted into the elastic substrate at equal intervals and fixedly connected to the elastic substrate at the insertion points. After insertion, the optical fiber exhibits a continuous wavy bend with identical shapes. One end of the optical fiber is connected to a light source, and the other end is connected to a photodiode. When the elastic substrate deforms in the direction of the optical fiber arrangement, it causes the optical fiber to bend and change its curvature. The width of the elastic substrate is 20-500 times the diameter of the optical fiber.

[0035] In this invention, the number of continuous wavy bends is 5-15; the continuous wavy bends are based on the elastic substrate as the reference plane; in two adjacent bends, one is located above the reference plane and the other is located below the reference plane; and during the deformation of the elastic substrate, the distance between any two adjacent intersection points is equal.

[0036] Let l be the distance between the two intersecting points when the elastic substrate is not stretched, and a be the maximum stretching ratio. Then, at the maximum elongation ratio, the distance between the two intersecting points is a×l. When using the transient displacement sensor of this invention for displacement monitoring, in order to simultaneously detect dynamic changes in tension and compression, the elastic substrate needs to be stretched by a ratio of b (0 < b < a) before the transient displacement sensor is installed. At this time, the distance between the two intersecting points is b×l. In a specific embodiment of this invention, when manufacturing the transient displacement sensor, the maximum pre-stretching ratio a is selected as 150%, b is preferably 120%-135%, and l is preferably 10mm. During measurement, in order to ensure measurement accuracy, it is desirable to control the change in the stretching ratio of the elastic substrate relative to b within 1.5%. Therefore, the displacement measurement range of the sensor for dynamic changes in tension and compression is 0-1.5mm; at the same time, the distance between the apex of the fiber bend and the elastic substrate is 4.925mm-5.075mm.

[0037] The elastic substrate is a braided elastic flat rope substrate. Optical fibers are inserted vertically into the elastic substrate at the same spacing, divided into a suspended part and a fixed part. The suspended part presents a continuous macro-bending ring. The optical fibers with taut ends are bonded to the stretched elastic rope only at the insertion point. After relaxation, the optical fibers form multiple out-of-plane macro-arches as the elastic rope is stretched. Each optical fiber inserted on it has several out-of-plane macro-arches (macro-bending rings, macro-arches). The normal direction of the surface where each out-of-plane macro-arch is located is perpendicular to the direction of the optical fiber, and they are evenly distributed on the upper and lower surfaces of the elastic substrate. When the elastic substrate transmits the vibration of the surface to be measured, it causes the left and right arch feet of the macro-arches of each optical fiber to approach and move away from each other, thereby changing the curvature of the macro-arches.

[0038] Based on the stability theory of compression members, this fiber optic macro-arch is a fixed-end structure. After the prestress of the elastic base is released, the deformation is symmetrical about the midpoint, and the reaction moments of the two arch legs are both M. e The approximate differential equation of the deflection curve is

[0039]

[0040] Where w is the deflection of any cross section of the optical fiber; x is the horizontal distance of any cross section of the optical fiber from the arch foot; M(x) is the bending moment of any cross section at a horizontal distance x from the arch foot; E is the Young's modulus of the optical fiber; I is the moment of inertia of the cross section; and F is the horizontal force on the arch foot of the optical fiber.

[0041] Reference marks The above formula can be written as

[0042]

[0043] This refers to the shape deflection curve of the fiber macro-arch; where k is an intermediate variable.

[0044] Preferably, the spacing of the optical fibers inserted on the braided elastic flat rope base is adjusted to present different sizes of arch curvature with different spacing.

[0045] Preferably, multiple parallel optical fibers can be arranged in the width direction of the braided elastic flat rope base, and the distance between the optical fibers can be adjusted as needed. Preferably, the elastic flat rope can undergo free deformation in the direction of optical fiber arrangement.

[0046] Preferably, the braided elastic flat rope substrate should be elastic, and its plastic deformation during use should be minimal or almost non-existent. It can be fixed together with the optical fiber material at the interlocking points using adhesive. Materials such as braided rubber rope, Ecoflex, and TPU can be selected. The width of the braided elastic flat rope substrate can be set between 1mm and 3mm to ensure that a single-point displacement signal can be collected at its end. When using quick-drying adhesive to bond the elastic flat rope to the surface to be tested, a narrower elastic flat rope can be selected due to the stronger fluidity of the adhesive. It is recommended that the width be between 20 and 500 times the diameter of the optical fiber. A narrower short side width will further improve measurement accuracy. In a specific embodiment of the present invention, the width of the tested elastic substrate is approximately 3mm, which is about 365 times the diameter of the SMF28 optical fiber used in this case.

[0047] More preferably, the braided elastic flat rope base is in a completely relaxed state in the initial state of the sensor, and can be partially stretched to the measurement linear region when placed on the surface of the object to be measured, and can contract or elongate with the surface of the object to be measured.

[0048] The optical fiber type can be SMF28; the insertion direction of multiple optical fibers on the elastic substrate should be kept as parallel as possible and consistent with the tension and compression direction of the elastic rope.

[0049] The range and sensitivity of the transient displacement sensor can be determined by the pre-stretch rate of the elastic substrate and the number of arched suspended areas through which the optical fiber is inserted. However, the maximum limit of the pre-stretch rate of the elastic substrate and the linear range limitation of the sensor itself need to be considered. Excessive tension or compression will exceed the measurement range of the sensor itself and may also cause adhesive bonding failure and optical fiber slippage or breakage.

[0050] The present invention also discloses a method for manufacturing the transient displacement sensor, which includes the following steps:

[0051] 1) Insert optical fibers perpendicularly into the upper and lower surfaces of the braided elastic flat rope substrate at the same spacing, with the insertion and extension direction being the stretching direction (i.e., the length direction) of the braided elastic flat rope substrate, and arrange the optical fibers in a straight line.

[0052] 2) The elastic substrate is stretched to the maximum elongation ratio. When the braided elastic flat rope substrate is stretched to the maximum elongation ratio, the optical fiber is straightened. The tensioned optical fiber (i.e. the straightened optical fiber) is attached to the upper and lower surfaces of the elastic substrate. At the current state of the optical fiber and the elastic rope intersecting position, 406 glue is used to fix the optical fiber and the elastic substrate together.

[0053] 3) Remove the stretching of the braided elastic flat rope base. The optical fibers that were originally attached to the elastic base bend into identical arches as the braided elastic flat rope base shrinks. Connect one end of the optical fiber to a light source and the other end to a photodiode to obtain the transient displacement sensor.

[0054] Preferably, when multiple optical fibers need to be arranged on a braided elastic flat rope base or the arranged optical fibers have macro-bend rings of different sizes, multiple optical fibers in the same direction can be arranged in parallel when inserting the optical fibers in step 1), or the size of the optical fiber macro-bend can be controlled by adjusting the interval distance when inserting the optical fibers.

[0055] Preferably, in step 2), the bonding method at the intersection of the optical fiber and the elastic substrate can be determined according to different elastic substrate materials. When the elastic substrate is braided rubber rope or TPU, glue can be used for bonding, such as 406 glue; when the elastic substrate is Ecoflex, UV-curing glue can be used for bonding.

[0056] This invention further discloses a method for transient displacement measurement using the aforementioned sensor. The specific method is as follows: a braided elastic flat rope substrate is pre-stretched along the fiber direction; during stretching, the elongation ratio of the elastic substrate is less than its maximum elongation ratio to avoid excessive stretching and breakage of the fiber or slippage failure at the glue bonding point; then, the two ends of the long side of the sensor's elastic substrate are perpendicularly bonded to the surface of the structure under test and a fixed structure surface, respectively; one end of the fiber is connected to a light source, and the other end is connected to a photodiode; the vibration signal of the surface of the structure under test in the direction of the fiber sensor is converted into a change in the curvature of the fiber macrobending, resulting in a change in macrobending loss. The curvature changes of several macrobendings will cause changes in the optical power received at the photodiode end. The photodiode converts the optical signal at the fiber end into an electrical signal, and the change in the electrical signal can be used to calculate the transient displacement change of the surface of the structure under test. Figure 2 As shown, in a specific embodiment of the present invention, the specific steps of the manufacturing process of the transient displacement sensor are as follows:

[0057] (1) As Figure 2As shown in (a), first take a braided rubber cord as an elastic base. Its length should be greater than the required number of macro arches multiplied by the distance between the arch feet. Insert the optical fiber at the same distance along the longitudinal axis of its upper surface. For the SMF28 optical fiber used in this example, it is recommended that the arch foot spacing be between 7mm and 13mm. It is recommended to use the method of making the arch foot spacing of 10mm.

[0058] (2) Figure 2 As shown in (b), the two ends of the elastic base with the inserted optical fiber are fixed to the maximum elongation ratio with clamps, taking care to keep it straight and not to twist; the two ends of the optical fiber are tensioned so that the macro-bend is in close contact with the upper and lower surfaces of the flat rope in this step; and for the common braided rubber filament flat rope used as the elastic base in this example, its maximum elongation ratio is 150%.

[0059] (3) Figure 2 As shown in (b), for the two macro-bend semi-loops at the beginning and end of the braided rubber filament flat rope, the optical fiber of the arch foot extension section must be kept in close contact with the braided rubber filament flat rope and aligned with the longitudinal axis direction of the braided rubber filament flat rope. It is recommended to use a small amount of instant adhesive to fix the optical fiber to the braided rubber filament flat rope at the arch foot of each macro-bend. A small amount of adhesive can avoid significantly affecting the shrinkage of the braided rubber filament flat rope. The instant adhesive used here can be 502, 406, etc., and different properties of adhesives can be selected according to the elastic substrate material used.

[0060] (4) Figure 2 As shown in (c)-(d), when the stretching at both ends of the braided rubber filament flat rope is removed, the braided rubber filament flat rope contracts, and the part that is not fixed to the braided rubber filament flat rope bends in the air to form macro-arches. The curvature and shape of the macro-arches are determined by the distance between their arch feet. When the braided rubber filament flat rope is stretched again, the distance between the arch feet increases, and the curvature of the macro-arches decreases until they are stretched again to a straight state that is completely in contact with the braided rubber filament flat rope. At this time, the curvature is reduced to almost 0.

[0061] like Figure 3 As shown Figure 2 The sensor calibration method and linearity region verification were performed. The displacement sensor proposed in this invention was placed on a one-dimensional displacement stage; the maximum elongation ratio in this example was 150%. The linearity of the sensor with 10 macro-bending loss arches was tested sequentially, with the arch spacing of the three sensors being 7mm, 10mm, and 13mm, respectively. A light source and a photodiode were connected to both ends of the optical fiber, respectively. To record the change in optical power in the optical fiber with sensor tension and compression, an oscilloscope was connected to the end of the photodiode, and the oscilloscope voltage change under one stretching and compression cycle was recorded. Figure 4 As shown. From Figure 4It can be seen that the changes in optical power and displacement of the three transient displacement sensors with different arch foot spacings exhibit a linear region during the stretching and contraction processes, and the R of the fitted straight line is... 2 A value close to 1 indicates excellent linearity. Calibration examples demonstrate the sensor's accuracy and linearity, providing the fundamental capability for measuring transient displacement under large deformations.

[0062] like Figure 5 The illustration shows an example of the transient response sensing of a cantilever beam under the impact of a steel ball, as described in this invention. One end of the elastic base of the one-dimensional sensor (with a 10mm arch spacing) is fixed to the measurement point on the upper surface of the cantilever beam, while the other end is fixed to a relatively stationary reference surface, ensuring the fiber direction is parallel to the normal direction of the cantilever beam's upper surface. A steel ball is gently struck at position A on the upper surface of the cantilever beam. The vibration of the upper surface causes the sensor to expand and contract, and the spacing between the arch feet of the fiber increases or decreases accordingly during this expansion and contraction. Throughout the process, the macro-bending rate of the fiber between the arch feet changes with the vibration of the cantilever beam and the vertical displacement of the upper surface. This change in curvature alters the amount of light leaking from the bend, thus allowing real-time monitoring of the optical power in the fiber to obtain the transient displacement of the cantilever beam. One end of the fiber is connected to a light source, and the other end is connected to a photodiode. The photodiode converts the optical signal into an electrical signal, which is displayed on an oscilloscope. Simultaneously, a Polytec Doppler vibration meter is set up, and a non-contact laser point is used to measure the out-of-plane displacement signal at the same point on the cantilever beam. An 8mm diameter steel ball was dropped from a height of 1cm onto the upper surface of the cantilever beam at position B as an external impact load, while oscilloscope signals and Doppler vibration meter signals were collected.

[0063] Figure 6 for Figure 5 The image shows a comparison between the oscilloscope measurement signal and the signal from a reliable Doppler vibration meter in a sensing example. The signal measured by the oscilloscope is the real-time conversion of the optical power signal of the fiber optic cable into an electrical signal. Through linearity, this signal can be used as the real-time displacement signal of the sensor's attachment position on the cantilever beam's upper surface. The linearity of the sensor has already been demonstrated. Figure 4 This is reflected in the text. Figure 6 As can be seen, the linearity of the transient displacement measurement on the entire upper surface of the cantilever beam is good, and the repeatability is high. This demonstrates the accuracy and precision of the sensor in transient displacement measurement, and also proves that the sensor of this invention can detect single-point displacement.

[0064] like Figure 7As shown, the design of this invention is biased towards practical applications. When users face measurement needs, they should determine the specific range and accuracy requirements of the required measurement scale based on the working scenario. Then, based on the required measurement range, the initial size of the elastic substrate, the maximum elongation ratio, and the spacing of the fiber macro-bending arch feet are selected to ensure that the stretching range covers the required measurement range, and according to... Figure 2 The sensor is manufactured using the process shown. Then, according to... Figure 3 The experimental setup diagram shows how to use a one-dimensional displacement platform to check if the linear region of the sensor covers the required displacement range for measurement. If the conditions are met, the design is complete; if not, first change the initial size of the elastic substrate to adjust the range of the linear sensitive region. If the conditions are still not met, change the stretch ratio of the elastic substrate. If the required range still cannot be achieved, the linear region range can be adjusted by changing the spacing between the fiber macro-arch feet or the number of macro-arches to meet the measurement requirements.

[0065] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A transient displacement sensor based on the uniform macro-bending loss of optical fiber and the dynamic changes in tension and compression of an elastic substrate, characterized in that, It includes an elastic substrate and an optical fiber interspersed on the elastic substrate; the optical fiber is interspersed on the elastic substrate at the same spacing and is fixedly connected to the elastic substrate at the interspersed point; after interspersing, the optical fiber presents a continuous wavy bend, and the bend shape is exactly the same; one end of the optical fiber is connected to a light source and the other end is connected to a photodiode. When the elastic substrate deforms along the length of the optical fiber, it causes the optical fiber to bend and change its curvature; the width of the elastic substrate is 20-500 times the diameter of the optical fiber. The continuous wavy bends are based on an elastic base as a reference plane; in two adjacent bends, one is located above the reference plane and the other is located below the reference plane. During the deformation of the elastic base, the distance between any two adjacent intersection points is equal.

2. The transient displacement sensor according to claim 1, characterized in that, The number of bends in the continuous wavy curve is 5-15.

3. The transient displacement sensor according to claim 1, characterized in that, The material used to make the elastic base is braided rubber rope, Ecoflex, or TPU.

4. The transient displacement sensor according to claim 1, characterized in that, The elastic substrate is in a partially stretched state in its initial state during application, and the elastic substrate can contract or elongate based on the initial state.

5. A method for manufacturing the transient displacement sensor according to claim 1, characterized in that, Includes the following steps: 1) Insert optical fibers at the same spacing onto an elastic substrate, wherein the length direction of the optical fibers is consistent with the length direction of the elastic substrate; and use the length direction of the elastic substrate as the direction of subsequent stretching; the width of the elastic substrate is 20-500 times the diameter of the optical fiber; 2) The elastic substrate is stretched to its maximum elongation ratio. Under the stretched state, the optical fiber is straightened and attached to the upper and lower surfaces of the elastic substrate. The optical fiber and the elastic substrate are fixed at the current insertion position of the optical fiber and the elastic substrate. 3) The stretching of the elastic substrate is removed. The optical fiber, which was originally attached to the elastic substrate, bends into identical arches as the elastic substrate contracts. The optical fiber as a whole contracts into a continuous wavy bend, with the elastic substrate as the reference plane. In two adjacent bends, one is above the reference plane and the other is below the reference plane. During the deformation of the elastic substrate, the distance between any two adjacent insertion points is equal. Connect one end of the optical fiber to a light source and the other end to a photodiode to obtain the transient displacement sensor.

6. The method for manufacturing a transient displacement sensor according to claim 5, characterized in that, In step 2), when the elastic base is braided rubber rope or TPU, glue is used for bonding; when the elastic base is Ecoflex, UV-curing glue is used for bonding.

7. A method for displacement measurement using the transient displacement sensor of claim 1, characterized in that, Includes the following steps: The elastic substrate is pre-stretched along the length of the optical fiber, and the elongation ratio of the elastic substrate during pre-stretching is less than the maximum elongation ratio of the elastic substrate. Then, one end of the long side of the elastic substrate in the pre-stretched state is vertically fixed to the surface of the structure to be tested, and the other end is vertically fixed to the surface of any fixed structure. One end of the optical fiber is connected to a light source, and the other end is connected to a photodiode. The displacement signal of the structure under test in the direction of the fiber arrangement will be transformed into the curvature change of the fiber bending. The curvature change of the fiber bending will eventually change the optical power signal received by the photodiode. The photodiode converts the optical power signal into an electrical signal output, that is, the transient displacement change of the surface of the structure under test is obtained.

8. The method for displacement measurement using a transient displacement sensor according to claim 7, characterized in that, During pre-stretching, the elongation ratio of the elastic substrate is 80%-90% of the maximum elongation ratio of the elastic substrate; when performing displacement measurement, the change in the elongation ratio of the elastic substrate relative to the elongation ratio of the elastic substrate during pre-stretching is controlled within 1.5%.

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