Optical fiber acceleration sensor based on F-P interference principle

Abstract

The utility model discloses an optical fiber acceleration sensor based on an F-P interference principle, relates to an optical fiber acceleration sensor, and aims to solve the problems of low sensitivity and poor measurement precision of the existing mechanical acceleration based on simple harmonic vibration. The base is provided with a mounting cavity; the sensing unit comprises an elastic membrane and a mass block; the outer edge of the elastic membrane is clamped in the mounting cavity of the base through the upper cover; the mass block is fixed in the center of the elastic membrane; a fixing through hole is formed in the upper cover; one end of the single-mode optical fiber penetrates into the mounting cavity of the base through the fixing through hole of the upper cover, the penetrating end of the single-mode optical fiber and the mass block are oppositely arranged, the surface of the mass block and the end face of the penetrating end of the single-mode optical fiber serve as two reflecting faces respectively, and an F-P interference cavity is formed by the space between the two reflecting faces. The beneficial effects are that the sensor is high in acceleration measurement sensitivity, and the measurement precision of acceleration measurement is improved.

Description

Technical Field

[0001] This utility model relates to an optical fiber accelerometer. Background Technology

[0002] Acceleration is a crucial parameter in physics and engineering. Its measurement has wide applications in many fields, such as missile guidance, aircraft navigation, satellite attitude control, and low-frequency acceleration measurement on the International Space Station in aerospace. In the automotive industry, it's used to determine the vehicle's cushioning performance, primarily for suspension systems, pre-braking / traction systems, driving systems, and safety systems. In power plants, it enables remote sensing of large electrical equipment, such as measuring internal components like engine transformers. Therefore, acceleration measurement has significant practical value.

[0003] Existing mechanical accelerometers based on simple harmonic oscillations suffer from drawbacks such as low sensitivity and large size, limiting their application. Fiber optic sensors, on the other hand, are an excellent type of sensor, offering a solution for their use in harsh environments. Fiber optic sensors are gaining increasing attention due to their advantages such as explosion-proof properties, resistance to electromagnetic interference, corrosion resistance, high temperature resistance, and compact structure. Fiber optic Fabry-Perot (FP) interferometers are among the oldest, most technologically mature, and most widely used fiber optic sensors, successfully used to measure parameters such as temperature, strain, pressure, displacement, ultrasound, and refractive index. In particular, fiber optic FP sensors offer unique advantages such as high accuracy, large measurement range, strong multiplexing capability, and fast response speed. Since many fields now require real-time, on-site, multi-parameter measurements, and accelerometers often require small size, light weight, high accuracy, and good stability, fiber optic accelerometers based on interferometry, due to their high accuracy and wide application range, have been a focus of research. However, miniaturization and high precision of these sensors have not yet been adequately addressed. Utility Model Content

[0004] The purpose of this invention is to solve the problems of low sensitivity and poor measurement accuracy of existing mechanical acceleration based on simple harmonic oscillation, and to propose a fiber optic accelerometer based on the FP interferometry principle.

[0005] The fiber optic accelerometer based on the FP interferometry principle described in this utility model includes a base, a top cover, a sensing unit, and a single-mode fiber.

[0006] The base is provided with a mounting cavity;

[0007] The sensitive unit includes an elastic diaphragm and a mass block;

[0008] The outer edge of the elastic diaphragm is held in the mounting cavity of the base by the upper cover; the mass block is fixed at the center of the elastic diaphragm.

[0009] The upper cover is provided with a fixing through hole;

[0010] One end of the single-mode fiber is inserted into the mounting cavity of the base through the fixing through hole of the top cover, and the inserted end of the single-mode fiber is positioned opposite to the mass block. The surface of the mass block and the end face of the inserted end of the single-mode fiber serve as two reflecting surfaces, and the space between the two reflecting surfaces constitutes an FP interference cavity.

[0011] Furthermore, this also includes ceramic ferrules;

[0012] The insertion end of the single-mode optical fiber is embedded in a ceramic ferrule.

[0013] Furthermore, threaded sleeves are also included;

[0014] The threaded sleeve is coaxially fixed in the fixing through hole of the upper cover, and the single-mode optical fiber passes through the threaded sleeve and is embedded in the ceramic ferrule.

[0015] Furthermore, it also includes sleeve fastening nuts;

[0016] One end of the sleeve fastening nut is fixed to the fixed through hole, and the sleeve fastening nut is located on the upper part of the threaded sleeve (6).

[0017] Furthermore, the elastic diaphragm includes an outer fixing ring and an inner fixing ring arranged concentrically, and the two are fixedly connected by four cantilever beams arranged in a cross shape.

[0018] The outer fixing ring is fixed between the base and the top cover by clamping;

[0019] The mass block is fixed on the inner fixing ring.

[0020] Furthermore, the mass block includes an upper mass block and a lower mass block;

[0021] The upper mass block and the lower mass block are fixed on both sides of the inner fixing ring by clamping, and the upper surface of the upper mass block and the end face of the insertion end of the single-mode optical fiber serve as two reflective surfaces respectively.

[0022] Furthermore, the width of the cantilever beam is 0.5 mm; the thickness of the cantilever beam is 0.15 mm.

[0023] The working principle of this utility model is as follows:

[0024] Light emitted from the light source is coupled through an optical fiber and enters the interference cavity from the non-penetrating end of the single-mode fiber. It undergoes multiple reflections between the upper surface of the mass block in the interference cavity and the end face of the penetrating end of the single-mode fiber, generating a multi-beam interference effect. When acceleration is applied to the fiber optic accelerometer based on the FP interference principle described in this invention, the mass block, acting as an inertial element, generates inertial force under the action of acceleration. Under the action of this inertial force, the elastic diaphragm deforms, causing a change in the FP cavity length, which in turn leads to a change in the interference signal. By measuring the change in the interference signal, the change in cavity length can be deduced, and the change in acceleration can be further demodulated to achieve acceleration sensing.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The fiber optic accelerometer based on the FP interferometry principle described in this invention features an adjustable FP interferometer cavity: the cavity length can be changed by adjusting the distance between the end face of the single-mode fiber insertion point and the upper surface of the mass block. Simultaneously, the elastic diaphragm in the sensing unit is fixed between the base and the top cover using a clamping assembly method, avoiding irreversible problems caused by gluing or welding. The modular design of the sensing unit facilitates disassembly and replacement, improving the sensor's maintainability and flexibility to adapt to different testing needs. Furthermore, the elastic diaphragm of the sensing unit adopts a cross-cantilever beam structure, which possesses good symmetry, uniform stress distribution, and resistance to lateral interference, effectively improving the sensor's linear response and directional selectivity. Therefore, this sensor exhibits high acceleration measurement sensitivity and improved acceleration measurement accuracy. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the overall structure of a fiber optic accelerometer based on the FP interferometry principle as described in Specific Implementation Method 1.

[0028] Figure 2 This is a three-dimensional structural diagram of the sensitive unit in Specific Implementation Method 1;

[0029] Figure 3 This is a schematic diagram of the assembled fiber optic FP accelerometer sensor in Specific Implementation Method 1.

[0030] Figure 4 The image shows the interferometric spectrum of the fiber optic FP accelerometer in Specific Implementation Method 1.

[0031] Figure 5 This is a schematic diagram of the linear fitting curve of the relationship between the magnitude of acceleration and the amount of wavelength shift at a frequency of 1000Hz in the first specific implementation method.

[0032] Figure 6This is a schematic diagram of the wavelength response of the sensor at a frequency of 1000Hz and an acceleration of 1g in the first specific implementation method.

[0033] Figure 7 This is a top view of the elastic diaphragm in Specific Implementation Method Five;

[0034] Figure 8 This is a cross-sectional view of the mass block in Specific Implementation Method Six.

[0035] In the figure, 1 is the base; 2 is the top cover; 3 is the sensing unit; 3-1 is the elastic diaphragm; 3-1-1 is the outer fixing ring; 3-1-2 is the cantilever beam; 3-1-3 is the inner fixing ring; 3-2 is the mass block; 3-2-1 is the upper mass block; 3-2-2 is the lower mass block; 4 is the ceramic ferrule; 5 is the single-mode optical fiber; 6 is the threaded sleeve; 7 is the sleeve fastening nut; 5-1 is the optical fiber accelerometer described in this utility model; 5-2 is the standard excitation table; 5-3 is the high-speed optical fiber sensor demodulator; 5-4 is the host computer. Detailed Implementation

[0036] Specific Implementation Method 1: Combination Figures 1 to 6 This embodiment describes an optical fiber accelerometer based on the FP interferometry principle, comprising a base 1, a top cover 2, a sensing unit 3, and a single-mode optical fiber 5.

[0037] The base 1 is provided with a mounting cavity;

[0038] The sensitive unit 3 includes an elastic diaphragm 3-1 and a mass block 3-2;

[0039] The outer edge of the elastic diaphragm 3-1 is clamped in the mounting cavity of the base 1 by the upper cover 2; the mass block 3-2 is fixed at the center of the elastic diaphragm 3-1;

[0040] The upper cover 2 is provided with a fixing through hole;

[0041] One end of the single-mode fiber 5 is inserted into the mounting cavity of the base 1 through the fixing through hole of the upper cover 2, and the inserted end of the single-mode fiber 5 is positioned opposite to the mass block 3-2. The surface of the mass block 3-2 and the end face of the inserted end of the single-mode fiber 5 serve as two reflecting surfaces, and the space between the two reflecting surfaces constitutes an FP interference cavity.

[0042] In this embodiment, see Figure 1The upper part of the base 1 is cylindrical, and the lower part is hexagonal. The base 1 is made of 304 stainless steel, which is inexpensive, readily available, and easy to disassemble and replace. The overall height of the base 1 is 25mm, and the maximum outer diameter is 20mm. The base 1 has an M5.0*8.0 mm thread, which facilitates the installation and fixation of the entire sensor onto the object to be measured. The upper cover 2 is cylindrical, and the fixing through hole has a threaded part machined by a tap. These threaded parts all participate in the installation of the sensor or the entire sensor. The upper cover 2 is made of 304 stainless steel, which is easy to disassemble and replace. The overall height of the top cover 2 is 13.5mm, and the maximum outer diameter of the top cover 2 is 20mm. The sensitive unit 3 is located in the center of the overall sensor. The sensitive unit 3 is fixed in the center of the sensor by the base 1 and the top cover 2. The sensitive unit 3 is placed into the mounting cavity of the base 1 with tweezers, and then the top cover 2 is installed. The top cover 2 is tightened with M3.0*5.0 mm hex screws, and the sensitive unit 3 is firmly fixed to the base 1 and the top cover 2.

[0043] See Figure 2 The sensing unit 3 comprises an elastic diaphragm 3-1 and a mass block 3-2. The elastic diaphragm 3-1 and the mass block 3-2 are assembled using the original mechanical structure and then bonded together with fiber optic curing adhesive 353ND. The bonded components are then placed on a 100°C heating stage for curing, ultimately forming the sensing unit 3. The sensing unit 3 is fixed between the base 1 and the top cover 2 using a clamping assembly method, avoiding irreversible problems associated with gluing or welding. The modular design facilitates the disassembly and replacement of the sensing unit 3, improving the sensor's maintainability and flexibility to adapt to different testing needs. Because of the modular design, the sensor's inherent frequency and sensitivity can be adjusted by changing its specific parameters, thus meeting the application requirements of different frequency or accuracy scenarios.

[0044] The performance of the FP interferometer cavity in the sensor largely depends on its two reflecting surfaces: the insertion end face of the single-mode fiber 5 and the upper surface of the mass block 3-2. The surface quality of these two optical surfaces directly affects the contrast of the interference fringes, cavity stability, and overall signal-to-noise ratio. Therefore, they must be meticulously polished and cleaned before assembly. The insertion end face of the single-mode fiber 5, as one end reflecting surface of the FP interferometer cavity, needs sufficient flatness to ensure the reflection and return of incident light. First, a coarse-grained polishing film is used to initially polish the insertion end face of the single-mode fiber 5 to remove cracks generated during the cutting process. Then, progressively finer polishing films are used to achieve a mirror-like finish. Finally, a digital microscope is used to check the flatness of the end face and for any remaining impurities. If any impurities are found, they are removed with anhydrous ethanol using a cotton swab to prevent residual impurities from interfering with the interference effect and to ensure good optical reflection performance. The upper surface of mass block 3-2 constitutes another reflecting surface of the FP cavity, and its surface quality also plays a decisive role in the interference effect. Mass block 3-2, which was processed in the previous section, is polished in the same way. After polishing, it is ultrasonically cleaned with anhydrous ethanol, carefully removed with tweezers, and placed on a heating table to dry, ensuring that there are no residues or fingerprints.

[0045] In this embodiment, the acceleration sensor is tested using a standard vibration table 5-2, a high-speed fiber optic sensor demodulator 5-3, and a host computer 5-4.

[0046] See Figure 1 The sensitive unit 3 is placed into the mounting cavity of the base 1 using tweezers. Then, the top cover 2 is installed and tightened with M3.0*5.0 mm hex screws. At this point, the outer edge of the elastic diaphragm 3-1 of the sensitive unit 3 is firmly fixed by the base 1 and the top cover 2. The single-mode fiber 5 is inserted into the mounting cavity of the base 1 through the fixing through-hole of the top cover 2. The length of the FP cavity formed by the end face of the single-mode fiber 5 and the upper surface of the mass block 3-2 is adjusted. The effect is observed using a high-speed fiber optic sensor demodulator 5-3. Initial locking is performed when a clear and bright interference spectrum appears, followed by fine-tuning, ultimately adjusting the cavity length to approximately 260 μm. (See also...) Figure 3 and Figure 4 Static interference spectroscopy was performed on the assembled fiber optic accelerometer 5-1. The interference spectrum was observed using a high-speed fiber optic sensor demodulator 5-3. The interference spectrum obtained in the 1525nm~1565nm range is as follows: Figure 4 As shown; by Figure 4As can be seen, the interference spectrum exhibits clear and uniformly distributed periodic interference fringes, and the fringe positions remain stable in the static state, indicating that the interference cavity structure is stable. Further analysis of the reflection spectrum intensity shows a maximum value of approximately -10 dB and a minimum value of approximately -37 dB, corresponding to a signal-to-noise ratio of approximately 27 dB. The fringe contrast is good, and the reflection characteristics are excellent. Figure 4 The results confirmed that the cavity performance met expectations. See also Figure 3 , Figure 5 Dynamic response testing was performed on the assembled fiber optic accelerometer 5-1, which was fixed to the standard excitation stage 5-2 with screws. During the experiment, a sinusoidal excitation signal of specific frequency and amplitude was output from the standard excitation stage 5-2 to drive the fiber optic accelerometer 5-1 to generate a dynamic response. The interference signal from the sensor was acquired in real time using a high-speed fiber optic sensor demodulator 5-3, and the wavelength value corresponding to a certain trough was tracked in real time using the single-peak tracking method. The wavelength value change at a certain trough when the sensor operates at an acceleration of 1g and a frequency of 1000 Hz is shown below. Figure 5 The obtained wavelength data is processed to analyze its acceleration characteristics. Finally, through analysis of sensitivity, linearity, and amplitude-frequency response curves, the overall performance of the fiber optic accelerometer 5-1 is verified. (See also...) Figure 3 , Figure 6 To verify the response performance of the fiber optic accelerometer 5-1 under vibration at a certain frequency, the fiber optic accelerometer 5-1 was fixed to the standard excitation table 5-2 with screws. A high-speed fiber optic sensor demodulator 5-3 with a scan rate of 50 kHz was used to track the spectral trough positions of the sensor output in real time, extracting the corresponding wavelength data. The acquired raw wavelength data was then smoothed and filtered, and further converted into wavelength drift. Finally, a fitting curve of the acceleration magnitude versus wavelength drift at a frequency of 1000 Hz was plotted as follows: Figure 6 As shown, the maximum deviation between the measured value and the linear fitting curve is calculated to evaluate the linearity of the fiber optic accelerometer 5-1. See also Figure 6 At 1000 Hz, the fiber optic accelerometer 5-1 exhibits a sensitivity of 0.317 nm / g and a linear correlation of 0.99998. Calculations show that the linearity of the fiber optic accelerometer 5-1 at 1000 Hz reaches 0.30%. This indicates that the fiber optic accelerometer 5-1 possesses excellent performance in the high-frequency band and features small size, light weight, high precision, and good stability.

[0047] Specific Implementation Method 2: This implementation method further defines the fiber optic accelerometer based on the FP interferometry principle described in Specific Implementation Method 1. In this implementation method, a ceramic ferrule 4 is also included.

[0048] The insertion end of the single-mode optical fiber 5 is embedded in the ceramic ferrule 4.

[0049] In this embodiment, a ceramic ferrule 4 is added, which is placed inside the mounting cavity of the base 1. The single-mode fiber 5 is inserted into the ceramic ferrule 4 and bonded using fiber optic adhesive 353ND. The two bonded components are then placed on a heating table at 100°C for heat curing. The insertion end face of the single-mode fiber 5 with the ceramic ferrule 4 is initially polished using a coarse-grained polishing film to remove cracks generated during the cutting process. Then, progressively finer polishing films are used to achieve a mirror-like end face. Finally, a digital microscope is used to check the flatness of the end face and whether there are any residual impurities. If there are any residual impurities, they are wiped away with anhydrous ethanol using a cotton swab to avoid interference with the interference effect and ensure good optical reflection performance.

[0050] Specific Implementation Method 3: This implementation method further defines the fiber optic accelerometer based on the FP interferometry principle described in Specific Implementation Method 2. In this implementation method, a threaded sleeve 6 is also included.

[0051] The threaded sleeve 6 is coaxially fixed in the fixing through hole of the upper cover 2, and the single-mode optical fiber 5 passes through the threaded sleeve 6 and is embedded in the ceramic ferrule 4.

[0052] In this embodiment, after the ceramic ferrule 4 containing the single-mode fiber 5 is installed into the threaded sleeve, it is bonded using fiber optic curing adhesive 353ND. The two bonded components are then placed on a heating table at 100°C for heat curing. Ultimately, the ceramic ferrule 4 containing the single-mode fiber 5 and the threaded sleeve 6 constitute an adjustable device for adjusting the cavity length of the FP. The external threads of the threaded sleeve 6 and the internal threads on the fixing through hole of the upper cover 2 form an adjustable structure for adjusting the length of the FP cavity.

[0053] Specific Implementation Method Four: This implementation method further defines the fiber optic accelerometer based on the FP interferometry principle described in Specific Implementation Method Three. In this implementation method, a sleeve fastening nut 7 is also included.

[0054] One end of the sleeve fastening nut 7 is fixed on the fixing through hole, and the sleeve fastening nut 7 is located on the upper part of the threaded sleeve 6.

[0055] In this embodiment, the sleeve fastening nut 7 is installed on the fixing through hole of the upper cover 2 to press the threaded sleeve 6, further locking the cavity length position, preventing cavity length drift or vibration loosening, and improving structural stability. The introduction of the threaded sleeve 6 structure realizes the fine adjustment and locking of the FP interference cavity length; by adjusting the thread depth, the distance between the insertion end face of the single-mode fiber 5 and the upper surface of the mass block 3-2 can be precisely controlled, and finally the cavity length position is fixed by the sleeve fastening nut 7.

[0056] Specific Implementation Method Five: Combination Figure 7 This embodiment further defines the fiber optic accelerometer based on the FP interferometry principle described in Specific Embodiment 3. In this embodiment, the elastic diaphragm 3-1 includes an outer fixing ring 3-1-1 and an inner fixing ring 3-1-3 arranged concentrically, and the two are fixedly connected by four cantilever beams 3-1-2 arranged in a cross shape.

[0057] The outer fixing ring 3-1-1 is fixed between the base 1 and the upper cover 2 by clamping;

[0058] The mass block 3-2 is fixed on the inner fixing ring 3-1-3.

[0059] In this embodiment, the sensor elastic diaphragm 3-1 serves as the core sensitive element of the FP accelerometer, and its geometry directly affects the sensor's resonant frequency and sensitivity. Four cantilever beams 3-1-2 form a cross-shaped cantilever beam structure. This structure possesses good symmetry, uniform stress distribution, and resistance to lateral interference, effectively improving the sensor's linear response and directional selectivity. The outer fixing ring 3-1-1 is used for clamping and fixing between the base 1 and the upper cover 2 to achieve overall fixation of the diaphragm 3-1. The inner fixing ring 3-1-3 is used to fix the mass block 3-2.

[0060] Specific Implementation Method Six: Combination Figure 8 This embodiment further defines the fiber optic accelerometer based on the FP interferometry principle described in Specific Embodiment 3. In this embodiment, the mass block 3-2 includes an upper mass block 3-2-1 and a lower mass block 3-2-2.

[0061] The upper mass block 3-2-1 and the lower mass block 3-2-2 are fixed on both sides of the inner fixing ring 3-1-3 by clamping. The upper surface of the upper mass block 3-2-1 and the end face of the insertion end of the single-mode fiber 5 serve as two reflecting surfaces of the FP cavity, which together form an interference cavity.

[0062] In this embodiment, the upper mass block 3-2-1 is coaxially fixed together by the first cylinder and the second cylinder; the lower mass block 3-2-2 is a cylindrical structure; the diameter of the first cylinder is less than or equal to the inner diameter of the inner fixing ring 3-1-3, and the outer wall of the first cylinder is provided with threads. At the same time, the inner wall of the cylindrical structure of the lower mass block 3-2-2 is machined with internal threads by tapping. The threads on the outer wall of the first cylinder match the internal threads on the inner wall of the cylindrical structure of the lower mass block 3-2-2; the diameter of the second cylinder is greater than the inner diameter of the inner fixing ring 3-1-3; the upper surface of the upper mass block 3-2-1 and the insertion end face of the single-mode optical fiber 5 serve as two reflecting surfaces of the FP interference cavity, which together constitute the FP interference cavity.

[0063] Specific Implementation Method Seven: This implementation method further defines the fiber optic accelerometer based on the FP interferometry principle described in Specific Implementation Method Three. In this implementation method, the width of the cantilever beam 3-1-2 is 0.5 mm, and the thickness of the cantilever beam 3-1-2 is 0.15 mm.

[0064] In this embodiment, the sensor elastic diaphragm 3-1 serves as the core sensitive element of the FP accelerometer. The thickness and width of the cantilever beam directly affect the resonant frequency and sensitivity of the sensor. The width of the cantilever beam is only 0.5 mm. In order to ensure high precision and no burrs, an electrical discharge wire cutting machine is used to process 65 Mn steel with a thickness of 0.15 mm. The cantilever beam of this size has good sensitivity.

[0065] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. An optical fiber acceleration sensor based on the F-P interference principle, characterized in that, It includes a base (1), a top cover (2), a sensitive unit (3), and a single-mode fiber (5); The base (1) is provided with an installation cavity; The sensitive unit (3) includes an elastic diaphragm (3-1) and a mass block (3-2); The outer edge of the elastic diaphragm (3-1) is held in the mounting cavity of the base (1) by the upper cover (2); the mass block (3-2) is fixed at the center of the elastic diaphragm (3-1); The upper cover (2) is provided with a fixing through hole; One end of the single-mode fiber (5) is inserted into the mounting cavity of the base (1) through the fixing through hole of the upper cover (2), and the insertion end of the single-mode fiber (5) is set opposite to the mass block (3-2). The surface of the mass block (3-2) and the end face of the insertion end of the single-mode fiber (5) serve as two reflecting surfaces, and the space between the two reflecting surfaces constitutes the FP interference cavity.

2. The fiber-optic acceleration sensor based on the F-P interference principle according to claim 1, characterized in that, It also includes ceramic ferrules (4); The insertion end of the single-mode optical fiber (5) is embedded in the ceramic ferrule (4).

3. The fiber optic accelerometer based on the FP interferometry principle according to claim 2, characterized in that, It also includes threaded sleeves (6); The threaded sleeve (6) is coaxially fixed in the fixing through hole of the upper cover (2), and the single-mode optical fiber (5) passes through the threaded sleeve (6) and is embedded in the ceramic ferrule (4).

4. The fiber-optic acceleration sensor based on the F-P interference principle according to claim 3, characterized in that, It also includes a sleeve fastening nut (7); One end of the sleeve fastening nut (7) is fixed on the fixed through hole, and the sleeve fastening nut (7) is located on the upper part of the threaded sleeve (6).

5. The fiber-optic acceleration sensor based on the F-P interference principle according to claim 1, characterized in that, The elastic diaphragm (3-1) includes an outer fixing ring (3-1-1) and an inner fixing ring (3-1-3) arranged concentrically, and the two are fixedly connected by four cantilever beams (3-1-2) arranged in a cross shape; The outer fixing ring (3-1-1) is fixed between the base (1) and the top cover (2) by clamping; The mass block (3-2) is fixed on the inner fixing ring (3-1-3).

6. The fiber-optic accelerometer based on the F-P interference principle according to claim 5, characterized in that, The mass block (3-2) includes an upper mass block (3-2-1) and a lower mass block (3-2-2); The upper mass block (3-2-1) and the lower mass block (3-2-2) are fixed on both sides of the inner fixing ring (3-1-3) in a clamping manner, and the upper surface of the upper mass block (3-2-1) and the end face of the insertion end of the single-mode optical fiber (5) serve as two reflective surfaces respectively.

7. The fiber-optic accelerometer based on the F-P interference principle according to claim 5, characterized in that, The width of the cantilever beam (3-1-2) is 0.5 mm; the thickness of the cantilever beam (3-1-2) is 0.15 mm.

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