A method for manufacturing a resonant fiber optic acceleration sensor

Abstract

The application discloses a preparation method of a resonant optical fiber acceleration sensor. The method comprises the following steps: firstly, a cantilever structure with a mass block area is formed on the end of a hollow tube; secondly, an elastic film is attached to the end surface of the cantilever structure; and finally, the cantilever on the cantilever structure is cut through the elastic film, so that the mass block area forms a suspended mass block suspended in the interference cavity through the elastic film. The preparation method can increase the attachment area of the elastic film, reduce the requirement for assembly precision, and the elastic film will not be deformed by the gravity of the mass block area during assembly, thereby avoiding the problems of relative inclination between the mass block and the end surface of the single-mode optical fiber and relative deviation between the mass block and the fiber core of the single-mode optical fiber.

Description

Technical Field

[0001] This invention relates to resonant fiber optic accelerometers, and more particularly to a method for fabricating a resonant fiber optic accelerometer. Background Technology

[0002] With the development of modern technology, accelerometers have expanded into various industries and become an indispensable sensor in inertial measurement systems. They are mainly used to measure numerous physical parameters such as force, mass, and displacement. Currently, in many fields such as inertial navigation, radar guidance, attitude measurement, and oil exploration, accelerometers are essential sensor components, and their performance plays a decisive role in the measurement accuracy and performance indicators of the system.

[0003] Resonant fiber optic accelerometers have seen rapid development in recent years. They utilize a mass block itself as the sensing element, forming a Fabry-Perot cavity with the fiber end face and the mass block end face. Acceleration is detected by measuring the cavity length change caused by the vibration of the mass block using intensity demodulation. They offer advantages such as simple structure and high sensitivity. For example, patent number CN201910189088.9 describes a pressure-sensitive graphene resonant fiber optic accelerometer, comprising an optical fiber, a ferrule, an elastic sheet, a sealing plug, a gas-sealed cavity, and a graphene film. The optical fiber is inserted at a certain distance from the lower end face of the ferrule. The fiber tip and the graphene film adsorbed on the lower end face of the ferrule form a Fabry-Perot interference cavity. The ferrule and the elastic sheet, as well as the elastic sheet and the gas-sealed cavity, are fixedly and completely connected, thus sealing the upper part of the cavity. The filling gas enters the sealed cavity through the air inlet on the lower side and is then sealed by the sealing plug. The acceleration to be measured acts on a ferrule with an optical fiber. The ferrule and the probe together act as additional mass, converting the acceleration into a concentrated force. This causes a displacement of the elastic sheet fixedly connected to the ferrule in the same direction as the acceleration. This displacement changes the volume of the sealed cavity, compressing the gas filling the cavity and causing a change in the cavity pressure. A graphene film adsorbed on the end face of the ferrule is stimulated by the excitation light guided by the optical fiber, reaching a resonant state with a certain vibration amplitude through photothermal excitation. This forms a Fabry-Perot interference cavity with a specific cavity length with the end face of the optical fiber. When the graphene film is subjected to pressure within the cavity, its in-plane stress changes, leading to changes in its resonant frequency and vibration amplitude, which in turn causes a change in the cavity length, ultimately resulting in a change in the intensity of the detected interference light. By detecting the change in the intensity of the interference light, the magnitude of the acceleration to be measured can be determined, thus achieving the measurement of the acceleration.

[0004] However, in the fabrication of resonant fiber optic accelerometers, it is necessary to first assemble and fix the mass block onto the elastic sheet, and then assemble and fix the elastic sheet onto the hollow tube. The elastic sheet is attached to the hollow tube only by its outer periphery, resulting in a small attachment area and high assembly precision requirements. Moreover, the mass block itself has weight, and the elastic sheet is easily deformed by the action of the mass block when it is assembled with the hollow tube, causing the assembled mass block to be relatively tilted relative to the end face of the optical fiber and to the core of the optical fiber. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides a method for fabricating a resonant fiber optic accelerometer, which can increase the attachment area of ​​the elastic film, reduce the requirements for assembly accuracy, and prevent the elastic film from deforming due to the gravity of the mass block region during assembly. This avoids the problems of relative tilting between the mass block and the end face of the single-mode fiber, as well as relative misalignment between the mass block and the core of the single-mode fiber.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0007] A method for fabricating a resonant fiber optic accelerometer includes the following steps:

[0008] Step 100: Connect one end face of a single-mode optical fiber to one end face of a hollow tube, and process the hollow tube to form an interference cavity of a predetermined length on the end face of the single-mode optical fiber.

[0009] Step 200: Connect one end face of a solid cylinder to the other end of the hollow tube, and process the solid cylinder to form a cantilever structure on the other end of the hollow tube. The cantilever structure includes a mass block region, a hollow region, a fixed region, and at least one cantilever. The mass block region is located inside the interference cavity. The fixed region is connected to the hollow tube. The hollow region is located between the mass block region and the fixed region to separate the mass block region and the fixed region. The cantilever is located between the mass block region and the fixed region to connect the mass block region and the fixed region.

[0010] Step 300: An elastic film is attached to and formed on the end face of the cantilever structure facing away from the hollow tube.

[0011] Step 400: Cut the cantilever on the cantilever structure through the elastic film, separating the mass block region and the fixed region of the cantilever structure, so that the mass block region forms a suspended mass block suspended in the interference cavity through the elastic film, wherein the end face of the single-mode fiber, the interference cavity and the end face of the mass block together constitute an FP interferometer.

[0012] Further, in step 100, the steps of connecting one end face of a single-mode optical fiber to one end face of a hollow tube and processing the hollow tube to form an interference cavity of a predetermined length on the end face of the single-mode optical fiber are as follows:

[0013] Step 110: Take a single-mode optical fiber and a hollow tube, and cut one end face of the single-mode optical fiber and one end face of the hollow tube flat.

[0014] Step 120: Weld the flattened end face of the single-mode optical fiber to the flattened end face of the hollow tube together;

[0015] Step 130: Cut the hollow tube to a predetermined length so that the cut hollow tube forms the interference cavity on the end face of the single-mode optical fiber.

[0016] Further, in step 200, the steps of connecting one end face of a solid cylinder to the other end of the hollow tube and processing the solid cylinder to form a cantilever structure on the other end of the hollow tube are as follows:

[0017] Step 210: Take a solid cylinder and cut one end face of the solid cylinder and the other end face of the hollow tube flat;

[0018] Step 220: Weld the flattened end face of the solid cylinder to the flattened end face of the hollow tube together;

[0019] Step 230: Thin the solid cylinder to a predetermined thickness;

[0020] Step 240: Etch the thinned solid column to form the cantilever structure.

[0021] Further, in step 230, the step of thinning the solid cylinder to a predetermined thickness is as follows:

[0022] Step 231: Cut the solid cylinder to the first thickness;

[0023] Step 232: Polish the end face of the solid cylinder to a predetermined thickness.

[0024] Furthermore, in step 232, the process of polishing the end face of the solid cylinder is as follows:

[0025] Step 2321: Under the end face grinding machine, the end face of the solid cylinder is polished with abrasive paper of the first grit size to reduce it to a predetermined thickness.

[0026] Step 2322: Under the end face grinding machine, the end face of the solid cylinder is polished with abrasive paper of the second grit size to make the end face smooth. The second grit size is smaller than the first grit size so that the end face of the solid cylinder becomes smooth after two polishing processes.

[0027] Step 2323: Clean the end face of the solid cylinder with hydrofluoric acid solution to remove debris from the polishing process.

[0028] Furthermore, in step 240, a femtosecond laser is used to etch the thinned solid cylinder.

[0029] Furthermore, the elastic film is a graphene film.

[0030] Further, in step 300, the step of attaching and forming the graphene film on the end face of the cantilever structure opposite to the hollow tube is as follows:

[0031] Step 301: The graphene film is grown on copper foil by chemical vapor deposition.

[0032] Step 302: Dissolve and etch the copper foil with ferric chloride solution to transfer the graphene film on the copper foil into the ferric chloride solution;

[0033] Step 303: Dilute and filter the ferric chloride solution containing the transferred graphene membrane with deionized water, so that the transferred graphene membrane floats on the deionized water;

[0034] Step 304: Slowly bring the end face of the cantilever structure close to the graphene film floating on the deionized water. After the end face of the cantilever structure has fully contacted the graphene film, slowly pull it away to transfer the graphene film to the end face of the cantilever structure.

[0035] Step 305: Dry the graphene film on the cantilever structure to attach the graphene film to the end face of the cantilever structure.

[0036] Further, in step 400, a femtosecond laser is used to cut the cantilever on the cantilever structure through the elastic film.

[0037] Furthermore, following step 400, the following steps are also included:

[0038] Step 500: Vacuum encapsulate the FP interferometer on the single-mode fiber.

[0039] The present invention has the following beneficial effects: When the elastic film is attached in this preparation method, in addition to its peripheral area being attached to the fixed area of ​​the cantilever structure, its central area can also be attached to the mass block area of ​​the cantilever structure. The attachment area of ​​the elastic film is large, which can reduce the requirements for assembly accuracy. Moreover, the mass block area is connected and fixed to the fixed area through the cantilever, and the weight of the mass block area is borne by the cantilever and the fixed area. Therefore, when the elastic film is assembled with the cantilever structure, it will not be deformed by the gravity of the mass block area. This avoids the problem of the mass block being relatively tilted relative to the end face of the single-mode fiber and relatively misaligned with the core of the single-mode fiber due to the deformation of the elastic film during assembly. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the steps of the fabrication method of the resonant fiber optic accelerometer provided by the present invention.

[0041] Figure 2 for Figure 1 The flowchart of step 100 in the fabrication method of the resonant fiber optic accelerometer shown is illustrated.

[0042] Figure 3 for Figure 1 The flowchart of step 200 in the fabrication method of the resonant fiber optic accelerometer shown is as follows.

[0043] Figure 4 for Figure 3 The flowchart of step 230 in the fabrication method of the resonant fiber optic accelerometer shown is as follows.

[0044] Figure 5 for Figure 4 The flowchart of step 232 in the fabrication method of the resonant fiber optic accelerometer shown is illustrated.

[0045] Figure 6 for Figure 1 The flowchart of step 300 in the fabrication method of the resonant fiber optic accelerometer shown is illustrated.

[0046] Figure 7 This is a schematic diagram showing the connection between the single-mode optical fiber and the hollow tube in the fabrication method of the resonant optical fiber accelerometer provided by the present invention.

[0047] Figure 8 This is a schematic diagram showing the connection of the single-mode optical fiber, hollow tube, and solid column in the fabrication method of the resonant optical fiber accelerometer provided by the present invention.

[0048] Figure 9This is a schematic diagram showing the connection of the single-mode fiber, hollow tube, and cantilever structure in the fabrication method of the resonant fiber optic accelerometer provided by the present invention.

[0049] Figure 10 A schematic diagram of the cantilever structure in the fabrication method of the resonant fiber optic accelerometer provided by the present invention.

[0050] Figure 11 This is a schematic diagram of the resonant fiber optic accelerometer provided by the present invention.

[0051] Figure 12 A flowchart illustrating the steps of another resonant fiber optic accelerometer fabrication method provided by the present invention.

[0052] Figure 13 for Figure 12 The flowchart of step 500 in the fabrication method of the resonant fiber optic accelerometer shown is illustrated.

[0053] Figure 14 This is a schematic diagram of another resonant fiber optic accelerometer provided by the present invention. Detailed Implementation

[0054] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0055] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] Example 1

[0059] like Figure 1 , 7 As shown in Figure 11, a method for fabricating a resonant fiber optic accelerometer includes the following steps:

[0060] Step 100: As Figure 7 As shown, one end face of a single-mode optical fiber 1 is connected to one end face of a hollow tube 2, and the hollow tube 2 is processed to form an interference cavity 21 of a predetermined length on the end face of the single-mode optical fiber 1.

[0061] Step 200: As Figure 8 and 9 As shown, one end face of a solid cylinder 3 is connected to the other end face of the hollow tube 2, and the solid cylinder 3 is processed to form a cantilever structure 31 on the other end face of the hollow tube 2, as shown. Figure 10 As shown, the cantilever structure 31 includes a mass block region 311, a hollow region 312, a fixed region 313, and at least one cantilever 314. The mass block region 311 is located inside the interference cavity 21. The fixed region 313 is connected to the hollow tube 2. The hollow region 312 is located between the mass block region 311 and the fixed region 313 to separate them. The cantilever 314 is located between the mass block region 311 and the fixed region 313 to connect them.

[0062] Step 300: An elastic film 4 is attached and formed on the end face of the cantilever structure 31 facing away from the hollow tube 2;

[0063] Step 400: Cut the cantilever 314 on the cantilever structure 31 through the elastic film 4, separating the mass block region 311 and the fixed region 313 of the cantilever structure 31, so that the mass block region 311 forms a suspended mass block 315 suspended in the interference cavity 21 through the elastic film 4, wherein the end face of the single-mode fiber 1, the interference cavity 21 and the end face of the mass block 315 together constitute the FP interferometer.

[0064] In this fabrication method for a resonant fiber optic accelerometer, a cantilever structure 31 with a mass block region 311 is first formed on the end of the hollow tube 2. Next, the elastic film 4 is attached to the end face of the cantilever structure 31. Finally, the cantilever 314 on the cantilever structure 31 is cut through the elastic film 4, so that the mass block region 311 forms a suspended mass block 315 suspended within the interference cavity 21 by the elastic film 4. Thus, when attaching the elastic film 4, in addition to its peripheral region being attached to the fixed region 313 of the cantilever structure 31, its central region can also be attached to the cantilever structure. On the mass block region 311 of structure 31, the attachment area of ​​the elastic film 4 is relatively large, which can reduce the requirements for assembly accuracy. Moreover, the mass block region 311 is connected and fixed to the fixed region 313 through the cantilever 314. The weight of the mass block region 311 is borne by the cantilever 314 and the fixed region 313. Therefore, when the elastic film 4 is assembled with the cantilever structure 31, it will not be deformed by the gravity of the mass block region 311. This avoids the problem of the mass block 315 being relatively tilted relative to the end face of the single-mode optical fiber 1 due to the deformation of the elastic film 4 during assembly, and the problem of relative misalignment with the fiber core 11 of the single-mode optical fiber 1.

[0065] During acceleration sensing, a probe light signal is coupled into the resonant fiber optic accelerometer from the other end face of the single-mode fiber 1. When the probe light signal in the single-mode fiber 1 passes through the end face of the single-mode fiber 1 in the FP interferometer, due to the difference in refractive index of the medium on both sides of the end face, part of the probe light signal is reflected back into the single-mode fiber 1, and part of the probe light signal enters the interference cavity 21 to continue propagating. When the probe light signal in the interference cavity 21 passes through the end face of the mass block 315 in the FP interferometer, due to the difference in refractive index of the medium on both sides of the end face, part of the probe light signal is reflected back into the interference cavity 21 and returns to the single-mode fiber 1 via the interference cavity 21, while the remaining probe light signal enters the external environment. The two probe light signals reflected back from the two end faces will interfere with each other due to the optical path difference, forming an interference light signal. When the resonant fiber optic accelerometer is placed in an acceleration environment, the mass block 315 will undergo relative displacement due to inertia and reciprocate under the action of the elastic film 4, thereby changing the cavity length of the interference cavity 21. This causes the cavity length of the interference cavity 21 to change periodically, resulting in spectral drift of the interference light signal. When the mass block 315 reciprocates, it modulates the intensity of the second probe light signal reflected by it. If a light signal of a certain wavelength in the spectrum is selected for observation, it can be found that the intensity of the light signal has changed, and the frequency of the intensity change of the light signal is consistent with the vibration frequency of the mass block 315. On an oscilloscope, this is a sine wave signal with the same frequency as the vibration frequency of the mass block 315. The magnitude and direction of acceleration in the acceleration environment can be calculated from the peak value of this sine wave signal.

[0066] The single-mode optical fiber 1 includes a core 11 and a cladding 12. The cladding 12 wraps around the outer peripheral surface of the core 11. The core 11 and the cladding 12 have different refractive indices so that the probe light signal can undergo total internal reflection at the interface between the core 11 and the cladding 12, and then be transmitted axially within the core 11.

[0067] The hollow tube 2 is connected to the end face of the cladding 12 of the single-mode optical fiber 1. The outer diameter of the hollow tube 2 is equivalent to the outer diameter of the cladding 12 of the single-mode optical fiber 1, and the inner diameter of the hollow tube 2 is larger than the outer diameter of the core 11 of the single-mode optical fiber 1. The interference cavity 21 is aligned with the end face of the core 11 of the single-mode optical fiber 1.

[0068] The end face of the mass block 315 is aligned with and parallel to the end face of the core 11 of the single-mode optical fiber 1.

[0069] Example 2

[0070] As an optimized solution of Embodiment 1, in this embodiment, the hollow tube 2 may be, but is not limited to, a hollow optical fiber or a quartz tube, and is connected to the end face of the single-mode optical fiber 1 by fusion splicing.

[0071] Specifically, such as Figure 2 As shown, in step 100, the steps of connecting one end face of a single-mode optical fiber 1 to one end face of a hollow tube 2 and processing the hollow tube 2 to form an interference cavity 21 of predetermined length on the end face of the single-mode optical fiber 1 are as follows:

[0072] Step 110: Take a single-mode optical fiber 1 and a hollow tube 2, and cut one end face of the single-mode optical fiber 1 and one end face of the hollow tube 2 flat.

[0073] In step 110, the lengths of the single-mode fiber 1 and the hollow tube 2 are not particularly limited. One end face of the single-mode fiber 1 and one end face of the hollow tube 2 are cut flat using a fiber optic cleaver so that the end faces and ends of the two can be seamlessly connected.

[0074] Step 120: Weld the flattened end face of the single-mode optical fiber 1 to the flattened end face of the hollow tube 2 together.

[0075] In step 120, the flattened end face of the single-mode fiber 1 and the flattened end of the hollow tube 2 are placed on both ends of the fiber optic fusion splicer, and then the fiber optic fusion splicer is operated to align the flattened end face of the single-mode fiber 1 with the flattened end of the hollow tube 2 and perform discharge fusion splicing.

[0076] Step 130: Cut the hollow tube 2 to a predetermined length so that the cut hollow tube 2 forms the interference cavity 21 on the end face of the single-mode optical fiber 1.

[0077] In step 130, the spliced ​​single-mode fiber 1 and hollow tube 2 are first placed on a two-dimensional moving platform. Under the monitoring of a CCD, the two-dimensional moving platform is controlled to move the single-mode fiber 1 and hollow tube 2 along the X and Y directions to adjust the relative position between the hollow tube 2 and the fiber cleaver. Then, the predetermined cutting point on the hollow tube 2 is moved to the fiber cleaver for cutting, with the X direction perpendicular to the Y direction.

[0078] After cutting, the length of the hollow fiber remaining on the single-mode fiber 1 is about 30 μm, that is, the initial cavity length of the interference cavity 21 is about 30 μm.

[0079] Example 3

[0080] As an optimized solution of Embodiment 1 or Embodiment 2, in this embodiment, the solid column 3 may be, but is not limited to, a quartz column or another single-mode optical fiber 1, and is connected to the end of the hollow tube 2 by fusion splicing.

[0081] Specifically, such as Figure 3 As shown, in step 200, the steps of connecting one end face of a solid column 3 to the other end of the hollow tube 2 and processing the solid column 3 to form a cantilever structure 31 on the other end of the hollow tube 2 are as follows:

[0082] Step 210: Take a solid cylinder 3 and cut one end face of the solid cylinder 3 and the other end face of the hollow tube 2 flat.

[0083] In step 210, the length of the solid column 3 is not particularly limited. One end face of the solid column 3 and the other end face of the hollow tube 2 are cut flat using a fiber optic cleaver so that the end faces and ends of the two can be seamlessly connected.

[0084] Step 220: Weld the flattened end face of the solid cylinder 3 to the flattened end face of the hollow tube 2.

[0085] In step 120, the flattened end face of the solid column 3 and the flattened other end of the hollow tube 2 are placed on both ends of the fiber optic fusion splicer, and then the fiber optic fusion splicer is operated to align the flattened end face of the solid column 3 with the flattened other end of the hollow tube 2 and then discharge fusion splice them.

[0086] Step 230: Thin the solid cylinder 3 to a predetermined thickness.

[0087] In step 230, the solid column 3 is thinned to a predetermined thickness, mainly to facilitate the subsequent etching process to manufacture the cantilever structure 31, and to reduce the weight of the final suspended mass block 315.

[0088] Specifically, such as Figure 4 As shown, in step 230, the step of thinning the solid cylinder 3 to a predetermined thickness is as follows:

[0089] Step 231: Cut the solid cylinder 3 to the first thickness.

[0090] In step 231, the spliced ​​single-mode fiber 1, hollow tube 2, and solid column 3 are first placed on a two-dimensional moving platform. Under the monitoring of a CCD, the two-dimensional moving platform is controlled to move the single-mode fiber 1, hollow tube 2, and solid column 3 along the X and Y directions to adjust the relative position between the solid column 3 and the fiber cleaver. Then, the predetermined cutting point on the solid column 3 is moved to the fiber cleaver for cutting, with the X direction perpendicular to the Y direction.

[0091] After cutting, the thickness of the solid column 3 remaining on the hollow tube 2 is about 20 μm.

[0092] Step 232: Polish the end face of the solid cylinder 3 to a predetermined thickness.

[0093] In step 232, the purpose of polishing the end face of the solid column 3 is twofold: one is to further reduce the thickness of the solid column 3, and the other is to reduce the roughness of the end face of the solid column 3 in order to improve the adhesion to the elastic film 4.

[0094] Specifically, such as Figure 5 As shown, in step 232, the process of polishing the end face of the solid cylinder 3 is as follows:

[0095] Step 2321: Under the end face grinding machine, the end face of the solid column 3 is polished with abrasive paper of the first grit size to reduce it to a predetermined thickness.

[0096] In step 2321, the first particle size is approximately 500 nm.

[0097] Step 2322: Under the end face grinding machine, the end face of the solid column 3 is polished with abrasive paper of the second particle size to make the end face smooth, wherein the second particle size is smaller than the first particle size.

[0098] In step 232, the second particle size is approximately 30 nm.

[0099] Step 2323: Clean the end face of the solid cylinder 3 with hydrofluoric acid solution to remove debris from the polishing process.

[0100] In step 2323, the concentration of the hydrofluoric acid solution is 2%, and the cleaning time is approximately 2 minutes.

[0101] Step 240: Etch the thinned solid column 3 to form the cantilever structure 31.

[0102] In step 240, a femtosecond laser is used to etch the thinned solid cylinder 3. The single-mode fiber 1 and the hollow tube 2 are clamped together and placed on a three-dimensional moving platform. The direction of the clamp is adjusted so that the end face of the solid cylinder 3 faces the focal point of the femtosecond laser beam. Then, the output power of the femtosecond laser is adjusted to output a femtosecond laser beam with appropriate energy, and the spot of the femtosecond laser is focused on the end face of the solid cylinder 3. Then, according to the etching trajectory data of the solid cylinder 3 (the three-dimensional shape data of the hollow area 312), the three-dimensional moving platform is controlled to move the solid cylinder along the X, Y, and Z directions to etch the solid cylinder 3 into the cantilever structure 31, with each of the X, Y, and Z directions being perpendicular to the others.

[0103] Example 4

[0104] As an improvement to Embodiment 1, Embodiment 2, or Embodiment 3, in this embodiment, the elastic film 4 is a graphene film, which is formed on the end face of the cantilever structure 31 by wet transfer attachment.

[0105] Specifically, such as Figure 6 As shown, in step 300, the step of attaching and forming the graphene film on the end face of the cantilever structure 31 facing away from the hollow tube 2 is as follows:

[0106] Step 301: The graphene film is grown on copper foil by chemical vapor deposition.

[0107] In step 301, the graphene film can be a single-layer structure, a few-layer structure, or a multi-layer structure.

[0108] Step 302: Dissolve and etch the copper foil with ferric chloride solution to transfer the graphene film on the copper foil into the ferric chloride solution.

[0109] In step 302, the concentration of the ferric chloride solution is about 0.08 g / ml. Only a small piece of copper foil needs to be cut according to the end face size of the cantilever structure 31 and placed in the ferric chloride solution for dissolution and corrosion. The graphene film on the cut copper foil should be able to cover the end face of the cantilever structure 31.

[0110] Step 303: Dilute and filter the ferric chloride solution containing the transferred graphene membrane with deionized water, so that the transferred graphene membrane floats on the deionized water.

[0111] In step 303, the main purpose of diluting and filtering the ferric chloride solution with deionized water is to clean the graphene membrane, avoid copper foil and ferric chloride residue on the graphene membrane, and reduce the pH of the solution.

[0112] Step 304: Slowly bring the end face of the cantilever structure 31 close to the graphene film floating on the deionized water. After the end face of the cantilever structure 31 is in complete contact with the graphene film, slowly pull it away to transfer the graphene film to the end face of the cantilever structure 31.

[0113] In step 304, the end face of the cantilever structure 31 should be slowly brought close to the graphene film floating on the deionized water in a manner parallel to the graphene film, so that the entire end face of the cantilever structure 31 is in uniform contact with the graphene film, thereby allowing the graphene film to be uniformly transferred and attached to the end face of the cantilever structure 31.

[0114] Step 305: Dry the graphene film on the cantilever structure 31 so that the graphene film adheres to the end face of the cantilever structure 31.

[0115] In step 305, the graphene film is allowed to dry naturally at room temperature. During the drying process, due to its own van der Waals forces, the graphene film will adhere tightly to the fixed area 313 and the mass block area 311 of the cantilever structure 31, while the graphene film located in the hollow area 312 will also be suspended due to its own van der Waals forces.

[0116] Example 5

[0117] As an optimization of Embodiment 1, Embodiment 2, Embodiment 3 or Embodiment 4, in this embodiment, in step 400, a femtosecond laser is used to cut the cantilever 314 on the cantilever structure 31 through the elastic film 4.

[0118] In step 400, when using a femtosecond laser to cut the cantilever 314 on the cantilever structure 31 through the elastic film 4, the single-mode fiber 1 and the hollow tube 2 are first clamped with a fixture and placed on a three-dimensional moving platform. The direction of the fixture is adjusted so that the surface of the elastic film 4 faces the focal point of the femtosecond laser spot. Then, the output power of the femtosecond laser is adjusted to output a femtosecond laser beam with appropriate energy, and the spot of the femtosecond laser is focused on the cantilever 314 of the cantilever structure 31 through the elastic film 4. Then, according to the etching trajectory data of the cantilever 314 (the three-dimensional shape data of the cantilever 314), the three-dimensional moving platform is controlled to move the elastic film 4 and the cantilever structure 31 along the X, Y, and Z directions to etch and cut the cantilever 314 on the cantilever structure 31. The X, Y, and Z directions are perpendicular to each other.

[0119] Since the femtosecond laser needs to etch the cantilever 314 through the elastic film 4, the position on the elastic film 4 corresponding to the cantilever 314 will be penetrated by the femtosecond laser. Therefore, the fewer the number of cantilever 314s on the cantilever structure 31, the better, and the smaller the width of the cantilever 314, the better. If it is necessary to reserve multiple cantilever 314s on the cantilever structure 31, each cantilever 314 should be evenly distributed around the mass block region 311, so that the perforations on the elastic film 4 corresponding to each cantilever 314 are evenly distributed, so as to avoid uneven stress distribution on the elastic film 4.

[0120] Example 6

[0121] As an optimization of Embodiment 1, Embodiment 2, Embodiment 3, Embodiment 4, or Embodiment 5, in this embodiment, such as Figure 12 and 14 As shown, after step 400, the preparation method further includes the following steps:

[0122] Step 500: Vacuum encapsulate the FP interferometer on the single-mode fiber 1.

[0123] In step 500, the FP interferometer on the single-mode fiber 1 may be vacuum-encapsulated using a vacuum tube 5, wherein the inner diameter of the vacuum tube 5 is between 250±6μm, which is larger than the outer diameter of the single-mode fiber 1 and the hollow tube 2.

[0124] Specifically, such as Figure 13 As shown, the steps for vacuum encapsulating the FP interferometer on the single-mode fiber 1 using vacuum tube 5 are as follows:

[0125] Step 510: Insert the FP interferometer on the single-mode fiber 1 into the vacuum tube 5.

[0126] In step 510, the single-mode fiber 1 and the vacuum tube 5 are placed on the left and right fiber supports of the carbon dioxide laser system, respectively. Then, the left and right fiber supports are controlled to move relative to each other under the carbon dioxide laser, so that the FP interferometer on the single-mode fiber 1 is inserted into the vacuum tube 5 under the carbon dioxide laser.

[0127] Step 520: Fusion the port of the vacuum tube 5 facing the single-mode optical fiber 1 onto the single-mode optical fiber 1.

[0128] In step 520, the carbon dioxide laser is turned on under appropriate parameters, so that the carbon dioxide laser emits carbon dioxide laser light and strikes the port of the vacuum tube 5 facing the single-mode fiber 1, so that the port is melted and fixed on the outer peripheral surface of the single-mode fiber 1.

[0129] Step 530: After evacuating the vacuum tube 5, seal the other end of the vacuum tube 5 facing away from the single-mode optical fiber 1.

[0130] In step 530, the other end of the vacuum tube 5 facing away from the single-mode fiber 1 is fixed in the vacuum chamber. After the vacuum chamber is activated to evacuate the vacuum tube 5 (the pressure is measured in real time using a vacuum gauge), the carbon dioxide laser is turned on again to emit carbon dioxide laser light and strike the other end of the vacuum tube 5 facing away from the single-mode fiber 1. This causes the other end to melt and then converge towards the center of the tube under negative pressure to form a sealed end.

[0131] Preferably, the internal air pressure of the vacuum tube 5 is less than 5*10^ -6 mbar.

[0132] This preparation method isolates the FP interferometer from the outside world by vacuum encapsulating it, thereby improving its service life. It also avoids the influence of external medium pressure, medium vibration, and water vapor on the measurement results, thus improving the measurement accuracy.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and not to limit them. Although the embodiments of the present invention have been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the embodiments of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a resonant fiber optic accelerometer, characterized in that, Includes the following steps: Step 100: Connect one end face of a single-mode optical fiber to one end face of a hollow tube, and process the hollow tube to form an interference cavity of a predetermined length on the end face of the single-mode optical fiber. Step 200: Connect one end face of a solid cylinder to the other end of the hollow tube, and process the solid cylinder to form a cantilever structure on the other end of the hollow tube. The cantilever structure includes a mass block region, a hollow region, a fixed region, and at least one cantilever. The mass block region is located inside the interference cavity. The fixed region is connected to the hollow tube. The hollow region is located between the mass block region and the fixed region to separate the mass block region and the fixed region. The cantilever is located between the mass block region and the fixed region to connect the mass block region and the fixed region. Step 300: An elastic film is attached to and formed on the end face of the cantilever structure facing away from the hollow tube. Step 400: Cut the cantilever on the cantilever structure through the elastic film, separating the mass block region and the fixed region of the cantilever structure, so that the mass block region forms a suspended mass block suspended in the interference cavity through the elastic film. The end face of the single-mode fiber, the interference cavity, and the end face of the mass block opposite to the end face of the single-mode fiber together constitute the FP interferometer.

2. The method for fabricating a resonant fiber optic accelerometer according to claim 1, characterized in that, In step 100, the steps of connecting one end face of a single-mode optical fiber to one end face of a hollow tube and processing the hollow tube to form an interference cavity of predetermined length on the end face of the single-mode optical fiber are as follows: Step 110: Take a single-mode optical fiber and a hollow tube, and cut one end face of the single-mode optical fiber and one end face of the hollow tube flat. Step 120: Weld the flattened end face of the single-mode optical fiber to the flattened end face of the hollow tube together; Step 130: Cut the hollow tube to a predetermined length so that the cut hollow tube forms the interference cavity on the end face of the single-mode optical fiber.

3. The method for fabricating a resonant fiber optic accelerometer according to claim 1, characterized in that, The steps for connecting one end face of a solid cylinder to the other end of the hollow tube, and processing the solid cylinder to form a cantilever structure on the other end of the hollow tube are as follows: Step 210: Take a solid cylinder and cut one end face of the solid cylinder and the other end face of the hollow tube flat; Step 220: Weld the flattened end face of the solid cylinder to the flattened end face of the hollow tube together; Step 230: Thin the solid cylinder to a predetermined thickness; Step 240: Etch the thinned solid column to form the cantilever structure.

4. The method for fabricating a resonant fiber optic accelerometer according to claim 3, characterized in that, In step 230, the step of thinning the solid cylinder to a predetermined thickness is as follows: Step 231: Cut the solid cylinder to the first thickness; Step 232: Polish the end face of the solid cylinder to a predetermined thickness.

5. The method for fabricating a resonant fiber optic accelerometer according to claim 4, characterized in that, In step 232, the process of polishing the end face of the solid cylinder is as follows: Step 2321: Under the end face grinding machine, the end face of the solid cylinder is polished with abrasive paper of the first grit size to reduce it to a predetermined thickness. Step 2322: Under an end face grinding machine, the end face of the solid cylinder is polished with abrasive paper of the second grit size to make the end face smooth, wherein the second grit size is smaller than the first grit size; Step 2323: Clean the end face of the solid cylinder with hydrofluoric acid solution to remove debris from the polishing process.

6. The method for fabricating a resonant fiber optic accelerometer according to claim 3, characterized in that, In step 240, a femtosecond laser is used to etch the thinned solid cylinder.

7. The method for fabricating a resonant fiber optic accelerometer according to claim 1, characterized in that, The elastic film is a graphene film.

8. The method for fabricating a resonant fiber optic accelerometer according to claim 7, characterized in that, In step 300, the step of attaching and forming the graphene film on the end face of the cantilever structure opposite to the hollow tube is as follows: Step 301: The graphene film is grown on copper foil by chemical vapor deposition. Step 302: Dissolve and etch the copper foil with ferric chloride solution to transfer the graphene film on the copper foil into the ferric chloride solution; Step 303: Dilute and filter the ferric chloride solution containing the transferred graphene membrane with deionized water, so that the transferred graphene membrane floats on the deionized water; Step 304: Slowly bring the end face of the cantilever structure close to the graphene film floating on the deionized water. After the end face of the cantilever structure has fully contacted the graphene film, slowly pull it away to transfer the graphene film to the end face of the cantilever structure. Step 305: Dry the graphene film on the cantilever structure to attach the graphene film to the end face of the cantilever structure.

9. The method for fabricating a resonant fiber optic accelerometer according to claim 1, characterized in that, In step 400, a femtosecond laser is used to cut the cantilever on the cantilever structure through the elastic film.

10. The method for fabricating a resonant fiber optic accelerometer according to claim 1, characterized in that, Following step 400, the following steps are also included: Step 500: Vacuum encapsulate the FP interferometer on the single-mode fiber.

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