Optical fiber acceleration sensor

Abstract

The utility model discloses a kind of optical fiber acceleration sensors, comprising: optical fiber component contains the side wall of closed shell extension into the inside of closed shell in one end of optical fiber Bragg grating;Elastomer component includes: shape matching elastomer and mass block, elastomer includes: center portion and respectively with the first vibration portion, second vibration portion connected with the both ends of center portion, elastomer both ends are fixedly connected with the both ends opposite in the inside of closed shell and with optical fiber component parallel, mass block is respectively set on center portion, first vibration portion and second vibration portion;Optical fiber component is respectively fixedly connected with the edge of first vibration portion and second vibration portion, and the first vibration portion and second vibration portion between optical fiber Bragg grating and with center portion interval preset distance.In keeping millimeter level package size, through innovative structure design breaks through dynamic sensitivity limit, simultaneously compatible narrow space installation demand, to solve the double predicament of " measurement uncertainty " " can not be installed " in power equipment vibration monitoring.

Description

Technical Field

[0001] This utility model relates to the field of vibration detection technology, and in particular to an optical fiber accelerometer. Background Technology

[0002] In the field of power equipment condition monitoring, complex electromagnetic environments pose a severe challenge to traditional sensors. Electrical sensors, such as piezoelectric accelerometers, are susceptible to electromagnetic interference affecting their measurement accuracy. This deficiency is particularly prominent in the vibration monitoring of stator windings in large rotating equipment such as steam turbines and generators. These devices operate in a multi-directional composite vibration environment, and faults such as loose bolts and insulation wear often manifest through abnormal vibrations, necessitating the use of highly reliable accelerometers for real-time monitoring.

[0003] Fiber optic sensing technology, with its advantages such as resistance to electromagnetic interference and corrosion, has gradually become the mainstream solution for condition monitoring of power equipment. Among them, fiber Bragg grating (FBG) accelerometers, due to their wavelength encoding characteristics, exhibit unique value under harsh conditions such as strong electromagnetic fields, high temperatures, and high pressures. However, existing FBG accelerometers face a fundamental contradiction: miniaturized sensors are limited by structural size, resulting in a significant reduction in dynamic sensitivity; while high-sensitivity sensors are often too large to be deployed in narrow spaces such as turbine winding gaps. This "sensitivity-size" trade-off severely restricts the application breadth of FBG sensors in complex industrial scenarios. Summary of the Invention

[0004] The purpose of this utility model embodiment is to provide a fiber optic accelerometer that, while maintaining a millimeter-level package size, overcomes the limitations of dynamic sensitivity through innovative structural design, is compatible with the installation requirements of narrow spaces, and has anti-electromagnetic interference characteristics. This solves the dual dilemma of "inaccurate measurement" and "insufficient installation" in vibration monitoring of power equipment, and provides reliable technical support for predictive maintenance of major equipment.

[0005] To address the aforementioned technical problems, this utility model provides an optical fiber accelerometer, comprising: a sealed housing, an optical fiber assembly, and an elastomer assembly;

[0006] The fiber optic assembly includes a fiber Bragg grating at one end, which extends into the interior of the enclosed housing through the side wall of the enclosed housing.

[0007] The elastomer assembly includes: a shape-matched elastomer and a mass block. The elastomer includes: a central portion and a first vibrating portion and a second vibrating portion respectively connected to both ends of the central portion. The two ends of the elastomer are fixedly connected to opposite ends inside the closed housing and are parallel to the optical fiber assembly. The mass block is respectively disposed on the central portion, the first vibrating portion and the second vibrating portion.

[0008] The optical fiber assembly is fixedly connected to the edges of the first vibrating part and the second vibrating part, respectively, and the optical fiber Bragg grating is located between the first vibrating part and the second vibrating part and at a predetermined distance from the center part.

[0009] Furthermore, the elastomer is an integral elastic film, and the elastic film between the central part and the first vibrating part and between the central part and the second vibrating part is provided with an arc-shaped arch bridge notch.

[0010] Furthermore, the elastomer assembly further includes: a first fixing member and a second fixing member;

[0011] The first vibrating part is fixedly connected to the inner wall of the closed housing through the first fixing member, and the second vibrating part is fixedly connected to the inner wall of the closed housing through the second fixing member.

[0012] Furthermore, the first fixing member and the second fixing member are each provided with a mass block.

[0013] Furthermore, the elastic membrane at the connection between the first vibrating part and the first fixing member, as well as the elastic membrane at the connection between the second vibrating part and the second fixing member, are both provided with arc-shaped arch bridge notches.

[0014] Furthermore, the material of the elastic film includes: zirconium oxide, gallium nitride, silicon carbide, quartz, gallium oxide, sapphire, or toughened ceramic.

[0015] Furthermore, the optical fiber assembly includes a plurality of optical fibers;

[0016] Each of the optical fibers passes through the sidewall of the enclosed housing and is fixedly connected to the edge of the first vibrating part and the edge of the second vibrating part.

[0017] Furthermore, the optical fiber assembly includes a first optical fiber and a second optical fiber;

[0018] The first optical fiber and the second optical fiber are fixedly connected to the edge of the first vibrating part and the two opposite sides of the second vibrating part, respectively.

[0019] The fiber Bragg gratings on the first optical fiber and the fiber Bragg gratings on the second optical fiber are respectively spaced apart from the two sides of the center portion that are perpendicular to the direction of the optical fiber assembly by the preset distance.

[0020] Furthermore, the elastomer includes a first elastomer, a second elastomer, and a third elastomer that are identical in shape and arranged in parallel.

[0021] The mass block is disposed and fixedly connected between the first elastic body and the second elastic body, and between the second elastic body and the third elastic body.

[0022] Furthermore, both the first and second vibrating parts are provided with connectors at their respective connection points to the optical fiber assembly;

[0023] Both the connecting seat of the first vibration part and the connecting seat of the second vibration part are planar structures parallel to the axial direction of the optical fiber assembly.

[0024] The sidewalls of the optical fiber assembly are respectively bonded to the connecting seats of the first vibration part and the second vibration part.

[0025] The above-described technical solution of this utility model embodiment has the following beneficial technical effects:

[0026] 1. Through innovative elastic structure design, especially the arch-shaped hinge at key connection points, vibration deformation is effectively concentrated and amplified. When the sensor is subjected to acceleration, the inertial force of the mass block drives the vibrating part to generate displacement. This displacement is efficiently converted into significant strain applied to the optical fiber through the optimized hinge structure. This enables the sensor to achieve an extremely compact size (suitable for installation in narrow spaces) while possessing dynamic response sensitivity far superior to traditional fiber optic accelerometers of the same size, solving the key contradiction of miniaturization and high sensitivity.

[0027] 2. A symmetrical dual-fiber sensing scheme is adopted, with the grating regions on the two fibers located on opposite sides of the vibration-sensitive structure. When vibration occurs, the two fibers generate strains in opposite directions (one in tension and one in compression). By demodulating these two differential signals, vibration information can be accurately extracted, while common-mode interference caused by environmental factors such as temperature changes can be automatically canceled. This significantly improves the measurement accuracy and long-term working stability of the sensor in complex environments (such as strong electromagnetic fields and temperature fluctuations).

[0028] 3. The core elastomer adopts a modular design concept combining multilayer thin films and mass blocks. By adjusting the number of layers of the elastic film and the size and distribution density of the mass blocks between each layer, key parameters such as the equivalent mass, stiffness, and resonant frequency of the entire sensor structure can be easily adjusted. This allows the sensor to be optimized and customized for different measurement ranges, frequency responses, and sensitivity requirements, greatly expanding its applicability in various industrial vibration monitoring scenarios. Attached Figure Description

[0029] Figure 1 This is a three-dimensional schematic diagram of the fiber optic accelerometer sensor provided in this embodiment of the utility model. Figure 1 ;

[0030] Figure 2 This is a three-dimensional schematic diagram of the fiber optic accelerometer sensor provided in this embodiment of the utility model. Figure 2 ;

[0031] Figure 3 This is a cross-sectional view of the fiber optic accelerometer sensor provided in an embodiment of this utility model.

[0032] Figure label:

[0033] 1. Elastomer assembly; 102. First vibrating part; 1031. First fixing part; 1032. Second fixing part; 104. Hinge part; 105. Second vibrating part; 106. Center part; 107. Connecting seat; 2. Fiber optic assembly; 201. Fiber Bragg grating; 202. Connecting part; 3. Enclosed housing; 301. Housing sidewall; 302. Wire hole; 4. Hole fixing sleeve. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this utility model. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of this utility model.

[0035] Please refer to Figure 1 , Figure 2 and Figure 3 This utility model provides an optical fiber accelerometer, including: a closed housing 3, an optical fiber assembly 2, and an elastomer assembly 1; the optical fiber assembly 2 includes an optical fiber Bragg grating 201, one end of which extends into the interior of the closed housing 3 through the side wall 301 of the closed housing 3; the elastomer assembly 1 includes: a shape-matched elastomer and a mass block, the elastomer includes: a central portion 106 and a first vibration portion 102 and a second vibration portion 105 respectively connected to the two ends of the central portion 106, the two ends of the elastomer are fixedly connected to the two opposite ends inside the closed housing 3 and are parallel to the optical fiber assembly 2, the mass block is respectively disposed on the central portion 106, the first vibration portion 102 and the second vibration portion 105; the optical fiber assembly 2 is fixedly connected to the edges of the first vibration portion 102 and the second vibration portion 105 respectively, the optical fiber Bragg grating 201 is located between the first vibration portion 102 and the second vibration portion 105 and is spaced at a predetermined distance from the central portion 106.

[0036] The structural design of the aforementioned fiber optic accelerometer is based on the principle of combining inertial sensing with fiber Bragg grating 201 (FBG) strain detection. The enclosed housing 3 provides mechanical protection and environmental isolation for the internal sensitive structure. Its sidewall 301 has a through-hole 302 for introducing and fixing the fiber optic assembly 2. The fiber optic assembly 2 includes at least one fiber embedded in the FBG, with both ends fixed to the edges of the first vibrating part 102 and the second vibrating part 105 of the elastomer assembly 1 via connecting parts 202, and is subjected to appropriate prestress to ensure effective strain transmission to the FBG region under minor deformation.

[0037] The elastomer assembly 1, as the core sensing unit of the sensor, consists of an elastomer and mass blocks distributed on it. The shape of each mass block matches the shape of a different part of the elastomer, and adjacent mass blocks are not connected. The elastomer has a central part 106 and a first vibrating part 102 and a second vibrating part 105 connected to its two sides, respectively. The whole assembly is fixed to the opposite sidewalls 301 inside the housing at both ends, forming a cantilever structure. The mass blocks are arranged on the central part 106 and the two vibrating parts to enhance the inertial response of the system. When the sensor is subjected to acceleration along with the measured object, the mass blocks exert a force on the elastomer due to inertia, causing the vibrating parts to bend and deform. This deformation further pulls the optical fiber fixed on it, causing axial strain in the FBG, thereby causing a shift in its Bragg wavelength. By demodulating this wavelength change, the magnitude of the external acceleration can be inferred.

[0038] The innovative structure described above overcomes the inherent trade-off between sensitivity and size in traditional FBG accelerometers. By distributing mass blocks across key areas of the elastic body and utilizing the flexible hinge design of the vibrating section, strain transfer efficiency and response sensitivity are significantly improved. Simultaneously, the FBG is positioned between the first vibrating section 102 and the second vibrating section 105, maintaining a certain distance from the central section 106, thus avoiding structural interference and facilitating strain concentration, thereby enhancing the signal-to-noise ratio. This layout can also be extended into a vertically symmetrical dual-fiber differential structure, effectively compensating for temperature drift and improving measurement stability and accuracy.

[0039] The above structure achieves high dynamic sensitivity and measurement accuracy while ensuring sensor miniaturization; the overall structure is robust and has strong anti-electromagnetic interference capability, making it suitable for vibration monitoring under complex working conditions such as power equipment and rotating machinery; the combination of the elastic body and the mass block has good designability, and can be adapted to different frequency response and measurement range requirements by adjusting the mass block parameters or structural layers, thus possessing good engineering adaptability and application prospects.

[0040] Furthermore, the elastomer is an integral elastic film, and the elastic film between the central part 106 and the first vibration part 102 and between the central part 106 and the second vibration part 105 is provided with an arc-shaped arch bridge notch.

[0041] From a working principle perspective, the integrated elastic diaphragm, as a single structure, forms hinge regions with specific mechanical properties through its arc-shaped arched notches. When the sensor is subjected to axial acceleration, the mass block exerts a force on the elastic body under inertia. These forces are transmitted and distributed through the hinge regions constructed by the arc-shaped arched notches. Due to the arc-shaped design of the arched notches, stress is concentrated and guided in the hinge regions, allowing the vibrating part to undergo more precise and controllable bending deformation around these hinges. This deformation method not only improves the efficiency of strain transmission but also ensures the linearity and repeatability of the deformation.

[0042] This innovative structure resolves the inherent trade-off between sensitivity and reliability prevalent in traditional sensors. The integrated structure avoids interface stress and assembly errors associated with multi-component assembly, significantly improving sensor consistency and long-term stability. The arc-shaped arch bridge notch design optimizes stress distribution, ensuring sufficient flexibility in the hinge area for adequate deformation while avoiding stress concentration at sharp corners, thus enhancing sensor fatigue life and measurement reliability. Furthermore, this structural design allows for precise control of sensor sensitivity and frequency response characteristics by adjusting the geometric parameters of the arch bridge notch (such as the radius of curvature and notch depth), facilitating performance optimization for various application scenarios.

[0043] The technological benefits of this structure are also significant. First, the arc-shaped arch gap acts as a strain concentration area, significantly improving the strain level sensed by the optical fiber, thereby enhancing the overall sensitivity of the sensor. Second, the one-piece molded elastomer structure offers better integrity and mechanical stability, ensuring the sensor's measurement consistency and accuracy under various environmental conditions. Third, this design improves the sensor's overload resistance and lifespan, as the arc-shaped stress transition effectively avoids material fatigue or damage caused by excessive local stress. Finally, this structure enables sensor miniaturization, achieving optimal mechanical performance within a limited space, making the sensor particularly suitable for applications with limited installation space.

[0044] Furthermore, the elastomer assembly 1 also includes: a first fixing member 1031 and a second fixing member 1032; the first vibration part 102 is fixedly connected to the inner wall of the closed housing 3 through the first fixing member 1031, and the second vibration part 105 is fixedly connected to the inner wall of the closed housing 3 through the second fixing member 1032.

[0045] The elastomer assembly 1 is fixedly connected to the inner wall of the enclosed housing 3 via a first fixing member 1031 and a second fixing member 1032, respectively. This design forms the core mounting and force transmission basis of the sensor. The fixing members provide stable and reliable boundary constraints for the elastomer, suspending and tensioning the entire elastomer assembly 1 (including the central part 106, the vibrating part, and the mass block) inside the housing. When the sensor is subjected to external acceleration excitation, the inertial force acts on the mass block, attempting to drive the vibrating part to produce relative displacement; while the rigid fixation provided by the fixing members restricts the overall rigid displacement of the elastomer, forcing the inertial force of the vibrating part to be completely converted into the bending strain of the elastic membrane (especially the hinge part), thereby efficiently converting the acceleration signal into structural deformation.

[0046] The main reason for adopting this split-type fastener structure instead of integral bonding is to ensure installation accuracy, repeatability, and long-term reliability. Independent fasteners facilitate the application of uniform and controllable preload to the elastomer during assembly, ensuring a stable connection to the housing and preventing performance degradation due to adhesive aging or uneven stress distribution. Simultaneously, rigid fixing minimizes energy loss at the mounting interface, allowing vibration energy to be more effectively concentrated in the hinge area, improving strain transmission efficiency and signal-to-noise ratio.

[0047] Furthermore, the first fixing member 1031 and the second fixing member 1032 are each provided with a mass block. Providing mass blocks on the first fixing member 1031 and the second fixing member 1032 is an important optimization for the sensor's inertial system. The additional mass blocks increase the effective mass of the sensor's fixed end (i.e., the boundary condition). When the sensor as a whole is subjected to acceleration, the mass blocks on the fixing members will generate an additional torque or force on the fixed part due to their inertia. This will change the local dynamic characteristics of the connection area between the elastic vibrating part and the fixed part, thereby modulating the bending deformation mode of the vibrating part under the action of inertial force, ultimately affecting the magnitude and distribution of strain transmitted to the optical fiber, achieving further adjustment and optimization of the sensor's sensitivity.

[0048] Furthermore, the elastic membrane at the connection between the first vibration part 102 and the first fixing member 1031, as well as the elastic membrane at the connection between the second vibration part 105 and the second fixing member 1032, are all provided with arc-shaped arch bridge notches.

[0049] At the connection points of the first vibrating part 102 and the first fixing member 1031, and at the connection points of the second vibrating part 105 and the second fixing member 1032, the elastic films of both employ a circular arc-shaped arch bridge notch design, which plays a crucial role in optimizing the mechanical transmission characteristics of the sensor. This circular arc notch forms a structural "hinge" at these critical connection points 202, acting as a carefully designed strain concentration area that effectively guides and limits the bending deformation mode of the elastic film under stress. When the vibrating part attempts to rotate or bend relative to the fixed fixing member under inertial force, the deformation will preferentially concentrate in these flexible arch bridge notch areas, thereby making the motion of the vibrating part more efficiently converted into tensile or compressive strain on the central region and the optical fiber.

[0050] The primary reason for employing this symmetrical and consistent notch design is to ensure the symmetry and linearity of the sensor's mechanical behavior. The notch structure at the connection point, together with the hinge at the central part 106, forms a complete flexible transmission system that jointly controls the deformation mode of the entire elastic body. This avoids stress concentration or undesirable vibration modes caused by sudden changes in local stiffness, thus ensuring a good linear relationship between the deformation of the vibrating part and the external acceleration, improving measurement accuracy. Secondly, this design is a necessary measure to ensure the reliability and durability of the sensor. The smooth, rounded transition greatly eliminates stress concentration phenomena that may be caused by sharp corners, significantly reducing the fatigue risk of the material under long-term alternating stress and extending the service life of the sensor.

[0051] The aforementioned structure not only optimizes the strain transmission path and improves the overall sensitivity of the sensor, but also greatly enhances the output consistency and stability of the sensor by giving the structure predictable and consistent deformation behavior. At the same time, it enhances the sensor's ability to resist lateral interference because it clearly defines the flexibility in the main sensing direction, while maintaining relatively high stiffness in other directions.

[0052] Specifically, the materials for elastic films include: zirconium oxide, gallium nitride, silicon carbide, quartz, gallium oxide, sapphire, or toughened ceramics.

[0053] Zirconia (ZrO2), gallium nitride (GaN), and silicon carbide (SiC) ceramic materials have been selected as the core substrates for elastic thin films due to their high Young's modulus (200-400 GPa) and low density (3-6 g / cm³). 3The unique combination of high modulus ensures that measurable deformation unit load deformation δ∝1 / E can be generated with micro-Newton inertial force, while the lightweight characteristics reduce the equivalent mass of the system, allowing the sensor resonant frequency to extend to higher frequencies f_n∝√(E / ρ). Taking zirconia as an example, its 200 GPa modulus at a film thickness of 50 μm can support a mass block 102 to generate a displacement response of 0.1 μm and an acceleration of 10 mg, while maintaining an operating bandwidth of over 10 kHz, meeting the broadband vibration monitoring requirements of power equipment.

[0054] When the thin film is subjected to acceleration load bending, piezoelectric polarization charges are generated inside the material, the intensity of which is proportional to the strain gradient. This charge signal can be synchronously demodulated with the FBG optical signal to form an electromechanical dual-mode sensing: the FBG provides the main vibration information, while the piezoelectric signal reflects the local stress distribution of the thin film in real time. More importantly, the two exhibit a negative correlation in their temperature response functions. The FBG wavelength drift coefficient is approximately 10 pm / ℃, and the GaN piezoelectric coefficient temperature gradient is -0.5% / ℃. Temperature drift self-compensation is achieved through a fusion algorithm, avoiding the space occupation introduced by an additional temperature sensor.

[0055] Quartz SiO2 and sapphire Al2O3, with their zero thermal expansion coefficient (0.5 ppm / ℃) and radiation-resistant lattice structure, are specifically designed for extreme environments such as nuclear power plants and spacecraft. The anisotropic properties of quartz thin films allow for the directional design of vibration-sensitive axes; its Z-cut wafers exhibit a resonant frequency drift of <0.1% for every 100℃ increase in temperature under thickness shear mode. Sapphire thin films maintain a tensile strength >500 MPa even at 800℃. Both materials are micromachined, such as through reactive ion etching, to form a micron-scale arched hinge 104, ensuring the linearity of hinge rotation in environments with strong radiation and a wide temperature range of -200 to 800℃, thus preventing sensitivity degradation caused by material creep.

[0056] Gallium oxide (Ga₂O₃), as an emerging ultrawide bandgap material, with its 8.8 eV bandgap, completely isolates carrier injection interference caused by strong electric fields in power equipment, and its leakage current is less than 10. -14 A. Its crystal plane has a lattice mismatch of only 3.7% with the optical fiber quartz material SiO2. Atomic-level bonding of the thin film-fiber interface can be achieved through molecular beam epitaxy, reducing the strain transfer loss of traditional adhesive interfaces from 15% to <2%. In humid sulfur-containing environments such as the steam side of a steam turbine, the corrosion rate of gallium oxide thin films is only 1 / 1000 that of stainless steel, ensuring the long-term stability of the sensor in corrosive atmospheres.

[0057] The elastic thin-film material system achieves robust sensor operation in complex industrial scenarios through precise matching of multi-physics field properties: high-modulus ceramic substrates provide ample deformation space at the microscale; the innovative fusion of electromechanical signals in semiconductor materials solves the temperature drift problem; the extreme environmental adaptability of quartz / sapphire expands application boundaries; and the interfacial atomic bonding and corrosion resistance of gallium oxide ensure long-term measurement accuracy. This material selection strategy enables the sensor to maintain vibration detection sensitivity fluctuations of <±3% under harsh conditions such as electromagnetic interference, high temperature and pressure, and corrosion radiation, overcoming the core technical bottleneck of environmental adaptability of miniature fiber optic sensors.

[0058] In one embodiment of this utility model, the optical fiber assembly 2 includes several optical fibers; each optical fiber passes through the side wall 301 of the enclosed housing 3 and is fixedly connected to the edge of the first vibrating part 102 and the edge of the second vibrating part 105. This arrangement constitutes the core sensing path for the sensor's light-to-force conversion. When the sensor is subjected to external acceleration excitation, the elastic vibrating part undergoes bending deformation, which is directly converted into axial tension or compression of the optical fiber fixed to its edge. Since the fiber Bragg grating 201 (FBG) is extremely sensitive to axial strain, this mechanical strain is converted into a shift in the wavelength reflected by the FBG. By demodulating these wavelength changes, the magnitude and direction of the acceleration can be accurately determined. The use of multiple optical fibers enables the system to achieve multi-axis measurement or differential signal detection.

[0059] This multi-fiber independent arrangement structure is adopted to improve signal quality, reliability, and functionality. Each fiber acts as an independent sensing channel, and their signals can be compared or combined for processing, providing a physical basis for eliminating common-mode interference (such as temperature changes). The fibers are fixed to the edge of the vibrating section because this area experiences the greatest strain amplitude during bending deformation, thereby maximizing the sensor's strain response and significantly improving its sensitivity. Furthermore, the multi-fiber design also provides the possibility of redundancy; the failure of a single fiber will not cause the entire sensor to fail, enhancing the system's robustness.

[0060] The aforementioned structure significantly improves the sensor's signal-to-noise ratio and measurement accuracy because differential processing based on multiple fiber signals effectively suppresses ambient noise. Secondly, this design achieves inherent temperature self-compensation; by comparing the temperature responses of different fibers or different locations within the same fiber, strain signals purely caused by acceleration can be separated. Furthermore, this layout increases the sensor's design freedom; for example, by adjusting the prestress or position of different fibers, its response characteristics to vibrations in specific directions or frequencies can be optimized. Finally, multi-channel detection provides richer data sources for subsequent signal processing algorithms, laying the foundation for developing more intelligent condition monitoring functions.

[0061] Specifically, the optical fiber assembly 2 includes a first optical fiber and a second optical fiber; the first optical fiber and the second optical fiber are fixedly connected to the edges of the first vibration part 102 and the two sides opposite to the second vibration part 105, respectively; the fiber Bragg grating 201 on the first optical fiber and the fiber Bragg grating 201 on the second optical fiber are respectively spaced at a preset distance from the two sides of the center part 106 that are perpendicular to the direction of the optical fiber assembly 2.

[0062] A dual-fiber symmetrical arrangement of the first and second optical fibers enables high-precision, interference-resistant acceleration measurement. Based on differential sensing and a temperature self-compensation mechanism, the first and second optical fibers are fixed to opposite sides of the edges of the first and second vibration units 102 and 105, respectively. When the sensor is subjected to axial acceleration, the elastic vibrating unit bends and deforms, causing one fiber to be stretched and the other compressed. This results in one wavelength of the two fiber Bragg gratings 201 (FBGs) drifting towards a longer wavelength and the other towards a shorter wavelength. Both FBGs are spaced a predetermined distance from the center of the elastic unit 106 in a direction perpendicular to the optical fibers. This distance ensures that the two gratings are in the most sensitive strain region, while avoiding contact interference with the center 106 and achieving maximum and symmetrical strain output. Based on this distance, subsequent processes such as real-time demodulation of the two wavelength changes and differential calculation can be performed to obtain a signal output proportional to the acceleration, while directly offsetting common-mode wavelength drift caused by environmental factors such as temperature changes.

[0063] The adoption of this precisely symmetrical dual-fiber layout and its specific positional relationship stems primarily from the extremely high requirements for measurement accuracy and environmental adaptability. Traditional single-fiber sensors cannot distinguish between spurious strain caused by temperature and genuine acceleration signals. This invention, through symmetrical arrangement and differential measurement, is a necessary means to improve the sensor's measurement accuracy under complex working conditions. By placing the two FBGs on opposite sides of the central part 106 and maintaining a preset distance, the symmetry and consistency of the strain field are precisely controlled, ensuring that the strain amplitude sensed by the two FBGs is equal but in opposite directions. This is the foundation for achieving efficient differential compensation and improving the linearity of the output signal.

[0064] In another embodiment of this utility model, the elastic body includes a first elastic body, a second elastic body, and a third elastic body that are of the same shape and arranged in parallel; a mass block is disposed between the first elastic body and the second elastic body, and between the second elastic body and the third elastic body, and is fixedly connected.

[0065] Furthermore, each of the first vibration part 102 and the second vibration part 105 is provided with a connecting seat 107 at the connection position with the optical fiber assembly 2; the connecting seat 107 of the first vibration part 102 and the connecting seat 107 of the second vibration part 105 are both planar structures parallel to the axis of the optical fiber assembly 2; the side wall 301 of the optical fiber assembly 2 is bonded to the connecting seat 107 of the first vibration part 102 and the connecting seat 107 of the second vibration part 105 respectively.

[0066] By employing a multi-layered elastomer structure composed of first, second, and third elastomers of identical shape arranged in parallel, and with mass blocks fixedly connected between each layer, the inertial sensitivity and signal quality of the sensor are significantly improved, constructing a composite vibration system with high inertial mass. When the sensor is subjected to axial acceleration, the mass blocks attempt to maintain their original motion state under inertial action, thereby applying a force to the multi-layered elastomers holding it. This causes the three elastomers to undergo coordinated bending deformation as a whole, and the motion of each vibrating part is synchronized and enhanced through the rigid connection of the mass blocks. This coordinated deformation is efficiently transmitted to the optical fiber fixed to the edge of the vibrating part, and is ultimately sensed by the FBG and converted into a wavelength signal.

[0067] This multi-layer sandwich structure is employed to achieve a breakthrough in sensor performance within an extremely limited space. Single elastic thin-film structures have limited inertial mass and stiffness, and sensitivity and resonant frequency often mutually restrict each other. By introducing parallel multi-layered elastomers and an intermediate mass block, this design significantly increases the total inertial mass of the system without significantly increasing the sensor's planar dimensions, thereby significantly improving the mechanical response amplitude to acceleration. More importantly, the mass block rigidly connects the multi-layered elastomers into a single unit, greatly enhancing the stiffness of the elastomer assembly 1 in the sensitive direction, effectively suppressing undesirable vibration modes, and ensuring the consistency and directionality of deformation—a necessary foundation for achieving high linearity and stability.

[0068] The aforementioned structure achieves synergistic optimization of sensitivity and resonant frequency. By obtaining a larger inertial mass within a miniaturized volume, the sensor maintains a high resonant frequency (i.e., wideband response) while achieving excellent low-frequency acceleration measurement sensitivity. Secondly, the symmetrical multilayer structure endows the sensor with extremely high output consistency and temperature stability, as the symmetrical mechanical structure allows temperature expansion effects to cancel each other out between layers, reducing interference with the measurement signal. Furthermore, the increased overall rigidity enhances the sensor's resistance to lateral interference and shocks, ensuring measurement reliability in complex vibration environments. Finally, this design provides a scalable architecture for the sensor; by adjusting the number of layers, thickness, or mass block parameters of the elastomer, the sensor's performance can be systematically customized to meet the demanding requirements of various applications, from precision instruments to industrial monitoring.

[0069] In addition, a hole fixing sleeve 4 is provided at the corresponding position of the fiber optic cable through the cable hole 302 on the side wall of the encapsulation housing. The hole fixing sleeve 4 is integrated into the inner wall of the cable hole 302 and forms a precision sealing system composed of a stepped clamp structure and a two-component filler adhesive. The inner diameter of the clamp is fitted with the outer diameter of the fiber (approximately 2-5 μm), and its stainless steel material provides rigid support. The filler adhesive is composed of an inner layer of silicone (elastic modulus 0.5 MPa) and an outer layer of epoxy resin (elastic modulus 3 GPa). When external tensile force is applied to the fiber, the silicone layer absorbs more than 80% of the stress through large deformation, and the residual force is blocked by the rigid clamp. Under vibration conditions, the damping characteristics of the silicone inhibit high-frequency fretting wear, and the epoxy layer prevents moisture penetration. The above methods reduce the force transmitted from the external 10N tensile force to the internal structure to <0.1N, while meeting the IP68 protection level.

[0070] This utility model embodiment aims to protect a fiber optic accelerometer sensor, and has the following effects:

[0071] 1. Through innovative elastic structure design, especially the arch-shaped hinge at key connection points, vibration deformation is effectively concentrated and amplified. When the sensor is subjected to acceleration, the inertial force of the mass block drives the vibrating part to generate displacement. This displacement is efficiently converted into significant strain applied to the optical fiber through the optimized hinge structure. This enables the sensor to achieve an extremely compact size (suitable for installation in narrow spaces) while possessing dynamic response sensitivity far superior to traditional fiber optic accelerometers of the same size, solving the key contradiction of miniaturization and high sensitivity.

[0072] 2. A symmetrical dual-fiber sensing scheme is adopted, with the grating regions on the two fibers located on opposite sides of the vibration-sensitive structure. When vibration occurs, the two fibers generate strains in opposite directions (one in tension and one in compression). By demodulating these two differential signals, vibration information can be accurately extracted, while common-mode interference caused by environmental factors such as temperature changes can be automatically canceled. This significantly improves the measurement accuracy and long-term working stability of the sensor in complex environments (such as strong electromagnetic fields and temperature fluctuations).

[0073] 3. The core elastomer adopts a modular design concept combining multilayer thin films and mass blocks. By adjusting the number of layers of the elastic film and the size and distribution density of the mass blocks between each layer, key parameters such as the equivalent mass, stiffness, and resonant frequency of the entire sensor structure can be easily adjusted. This allows the sensor to be optimized and customized for different measurement ranges, frequency responses, and sensitivity requirements, greatly expanding its applicability in various industrial vibration monitoring scenarios.

[0074] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of this utility model and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of this utility model should be included within its protection scope. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A fiber optic accelerometer, characterized in that, include: Enclosed housing (3), fiber optic assembly (2), and elastomer assembly (1); The fiber optic assembly (2) includes a fiber Bragg grating (201) at one end, which extends into the interior of the enclosed housing (3) through the sidewall (301) of the enclosed housing (3); The elastomer assembly (1) includes: a shape-matched elastomer and a mass block. The elastomer includes: a central part (106) and a first vibration part (102) and a second vibration part (105) respectively connected to both ends of the central part (106). The two ends of the elastomer are fixedly connected to the opposite ends inside the closed shell (3) and are parallel to the optical fiber assembly (2). The mass block is respectively disposed on the central part (106), the first vibration part (102) and the second vibration part (105). The optical fiber assembly (2) is fixedly connected to the edges of the first vibration part (102) and the second vibration part (105) respectively. The fiber Bragg grating (201) is located between the first vibration part (102) and the second vibration part (105) and is spaced at a predetermined distance from the center part (106).

2. The fiber optic accelerometer sensor according to claim 1, characterized in that, The elastomer is an integral elastic film, and the elastic film between the central part (106) and the first vibration part (102) and between the central part (106) and the second vibration part (105) is provided with an arc-shaped arch bridge notch.

3. The fiber optic accelerometer sensor according to claim 2, characterized in that, The elastomer assembly (1) further includes: a first fastener (1031) and a second fastener (1032); The first vibration part (102) is fixedly connected to the inner wall of the closed shell (3) through the first fixing member (1031), and the second vibration part (105) is fixedly connected to the inner wall of the closed shell (3) through the second fixing member (1032).

4. The fiber optic accelerometer sensor according to claim 3, characterized in that, The first fixing member (1031) and the second fixing member (1032) are respectively provided with mass blocks.

5. The fiber optic accelerometer sensor according to claim 3, characterized in that, The elastic membrane at the connection between the first vibration part (102) and the first fixing member (1031) and the elastic membrane at the connection between the second vibration part (105) and the second fixing member (1032) are both provided with arc-shaped arch bridge notches.

6. The fiber optic accelerometer sensor according to claim 2, characterized in that, The materials of the elastic film include: zirconium oxide, gallium nitride, silicon carbide, quartz, gallium oxide, sapphire, or toughened ceramic.

7. The fiber optic accelerometer according to any one of claims 1-6, characterized in that, The optical fiber assembly (2) includes several optical fibers; Each of the optical fibers passes through the sidewall (301) of the enclosed housing (3) and is fixedly connected to the edge of the first vibration part (102) and the edge of the second vibration part (105).

8. The fiber optic accelerometer sensor according to claim 7, characterized in that, The optical fiber assembly (2) includes a first optical fiber and a second optical fiber; The first optical fiber and the second optical fiber are fixedly connected to the edge of the first vibration part (102) and the two sides opposite to the second vibration part (105), respectively. The fiber Bragg grating (201) on the first fiber and the fiber Bragg grating (201) on the second fiber are respectively spaced apart from the two sides of the center part (106) in the direction perpendicular to the fiber assembly (2) by the preset distance.

9. The fiber optic accelerometer according to any one of claims 1-6, characterized in that, The elastomer includes a first elastomer, a second elastomer, and a third elastomer that are identical in shape and arranged in parallel. The mass block is disposed and fixedly connected between the first elastic body and the second elastic body, and between the second elastic body and the third elastic body.

10. The fiber optic accelerometer according to any one of claims 1-6, characterized in that, Both the first vibration part (102) and the second vibration part (105) are provided with a connector (107) at the connection positions with the optical fiber assembly (2); The connecting seat (107) of the first vibration part (102) and the connecting seat (107) of the second vibration part (105) are both planar structures parallel to the axial direction of the optical fiber assembly (2); The sidewall (301) of the optical fiber assembly (2) is bonded to the connecting seat (107) of the first vibration part (102) and the connecting seat (107) of the second vibration part (105), respectively.

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