Optical fiber pressure sensor and method of manufacturing the same

Abstract

This invention discloses an optical fiber pressure sensor, comprising a single-mode optical fiber, a microcavity device, and a metal thin film. The microcavity device has an optical microcavity and a first port and a second port respectively connected to both ends of the optical microcavity. The first port of the microcavity device is connected to one end face of the single-mode optical fiber, and the second port of the microcavity device is connected to the metal thin film. A metal bonding layer is formed on the second port of the microcavity device by vapor deposition. The metal thin film is welded and fixed to the metal bonding layer of the microcavity device and suspended in front of the optical microcavity. This optical fiber pressure sensor can improve the bonding force between the metal thin film and the microcavity device. This invention also provides a method for fabricating the above-mentioned optical fiber pressure sensor.

Description

Technical Field

[0001] This invention relates to fiber optic sensing technology, and more particularly to a fiber optic pressure sensor and its fabrication method. Background Technology

[0002] In fields such as aerospace, medical monitoring, and explosion damage assessment, pressure detection technology is crucial for many engineering applications. Currently, the mainstream electrical sensors on the market include piezoelectric and piezoresistive pressure sensors. However, electrical sensors cannot operate for extended periods in harsh environments such as high electromagnetic interference and high ionizing radiation, and are easily affected by ambient temperature, resulting in poor stability.

[0003] Fiber optic sensing technology is one of the major inventions of the latter half of the 20th century. Fiber optic sensors are characterized by their small size, light weight, resistance to electromagnetic interference, and corrosion resistance. They have been widely used in the measurement of physical quantities such as pressure, strain, acceleration, and magnetic fields. Currently, in the field of pressure sensing technology, there are structures based on fiber Bragg gratings (FBGs) and Fabry-Perot interferometers (FPIs). Compared to fiber Fabry-Perot interferometer (FPI) pressure sensors, FBG pressure sensors have lower sensitivity and are more difficult to manufacture. Fiber Fabry-Perot interferometer (FPI) pressure sensors are often combined with a sensitive thin film to form a pressure-sensitive interference cavity. External pressure causes deformation of the sensitive thin film, thereby changing the cavity length. Pressure sensing is achieved by demodulating the cavity length change, resulting in higher pressure sensitivity and making it more suitable for single-point high-precision pressure sensing.

[0004] To improve the sensitivity of fiber optic Fabry-Perot interferometers (FPIs), a thin metal film is typically used as the sensing film. The metal film is formed on the interferometer cavity using a wet transfer method and then fixed to the cavity by van der Waals forces after drying. However, the bond between the metal film and the interferometer cavity formed by van der Waals forces is not strong, making it easy for the metal film to detach from the cavity during pressure sensing. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides an optical fiber pressure sensor that can improve the bonding force between the metal thin film and the microcavity device.

[0006] The present invention also provides a method for preparing the above-mentioned fiber optic pressure sensor.

[0007] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0008] An optical fiber pressure sensor includes a single-mode optical fiber, a microcavity device, and a metal thin film. The microcavity device has an optical microcavity and a first port and a second port respectively connected to both ends of the optical microcavity. The first port of the microcavity device is connected to one end face of the single-mode optical fiber, and the second port of the microcavity device is connected to the metal thin film. A metal bonding layer is formed on the second port of the microcavity device by vapor deposition. The metal thin film is welded and fixed to the metal bonding layer of the microcavity device and suspended in front of the optical microcavity of the microcavity device.

[0009] Furthermore, the inner diameter of the microcavity device is equal to the diameter of the single-mode optical fiber, and the first port of the microcavity device is inserted and fixed to the end face of the single-mode optical fiber.

[0010] Furthermore, an optical adhesive is applied between the first port of the microcavity device and the outer wall of the single-mode optical fiber for bonding and fixing, and a sealant is applied to the optical adhesive for sealing and fixing.

[0011] Furthermore, the metal thin film includes a peripheral region and a central region, the peripheral region surrounding the central region; the peripheral region is welded and fixed to the metal solder layer of the microcavity device, and the central region is suspended in front of the optical microcavity of the microcavity device.

[0012] Furthermore, the metal solder layer includes a chromium solder layer, and the metal film includes a gold-tin alloy film.

[0013] A method for fabricating an optical fiber pressure sensor includes the following steps:

[0014] Step 100: Take a microcavity device, the microcavity device having an optical microcavity and a first port and a second port respectively connected to both ends of the optical microcavity;

[0015] Step 200: A metal solder layer is formed on the second port of the microcavity device by vapor deposition;

[0016] Step 300: A thin metal film is formed on the metal bonding layer of the microcavity device by wet transfer and suspended in front of the optical microcavity of the microcavity device;

[0017] Step 400: Heat the microcavity device to weld the metal solder layer and the metal film together on the microcavity device;

[0018] Step 500: Connect the end face of a single-mode optical fiber to the first port of the microcavity device.

[0019] Furthermore, in step 300, the step of forming a thin metal film on the metal bonding layer of the microcavity device by wet transfer and suspending it in front of the optical microcavity of the microcavity device is as follows:

[0020] Step 310: Form the metal thin film on a copper-based foil by vapor deposition;

[0021] Step 320: Dissolve and corrode the copper-based foil using a sulfuric acid solution, so that the metal film on the copper-based foil is transferred into the sulfuric acid solution;

[0022] Step 330: Dilute and filter the sulfuric acid solution containing the transferred metal film with deionized water, so that the metal film in the sulfuric acid solution floats on the deionized water;

[0023] Step 340: Slowly bring the second port of the microcavity device with the metal solder layer close to the metal film floating on the deionized water. After the metal solder layer of the microcavity device contacts the metal film, slowly pull it away to transfer the metal film onto the metal solder layer of the microcavity device.

[0024] Step 350: Dry the metal film on the microcavity device to bond the metal film to the metal solder layer of the microcavity device and suspend it in front of the optical microcavity of the microcavity device.

[0025] Furthermore, the inner diameter of the microcavity device is equal to the diameter of the single-mode optical fiber. In step 500, one end of the single-mode optical fiber is inserted and fixed between the microcavity device and the first port.

[0026] Furthermore, the step of inserting and fixing one end of the single-mode optical fiber to the first port of the microcavity device is as follows:

[0027] Step 510: Cut one end face of the single-mode optical fiber flat;

[0028] Step 520: Insert the flattened end face of the single-mode fiber into the optical microcavity of the microcavity device from the first port of the microcavity device;

[0029] Step 530: Couple the detection light into the single-mode fiber from the other end face of the single-mode fiber, and collect the reflected light reflected back from the other end face of the single-mode fiber to obtain the interference spectrum of the emitted light;

[0030] Step 540: Adjust the insertion depth of the single-mode fiber in the microcavity device until the interference spectrum changes to the preset initial spectrum;

[0031] Step 550: Apply optical adhesive between the first port of the microcavity device and the outer wall of the single-mode optical fiber for bonding and fixation;

[0032] Step 560: Apply sealant to the optical adhesive for sealing and fixation.

[0033] Furthermore, the metal solder layer includes a chromium solder layer, and the metal film includes a gold-tin alloy film.

[0034] The present invention has the following beneficial effects: The fiber optic pressure sensor of this patent first forms a metal bonding layer on the second port of the microcavity device by vapor deposition, and then fixes the metal thin film to the metal bonding layer of the microcavity device by welding, so that the metal thin film is suspended in front of the optical microcavity of the microcavity device. Since the metal thin film is bonded to the microcavity device by welding to the metal bonding layer, compared with the prior art where the metal thin film is bonded to the microcavity device by van der Waals forces, the bonding is larger and stronger. Moreover, since the metal bonding layer is formed on the second port of the microcavity device by vapor deposition, in addition to van der Waals forces, there are also interaction forces generated by ionic bonds, covalent bonds, and metallic bonds formed during vapor deposition between the metal bonding layer and the microcavity device, which greatly improves the firmness of the bond between the metal thin film and the microcavity device. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the fiber optic pressure sensor provided by the present invention.

[0036] Figure 2 This is an exploded view of the fiber optic pressure sensor provided by the present invention.

[0037] Figure 3 A flowchart illustrating the steps of the fabrication method of the fiber optic pressure sensor provided by the present invention.

[0038] Figure 4 This is a step-by-step flowchart of step 300 in the method for preparing the fiber optic pressure sensor provided by the present invention.

[0039] Figure 5 This is a step-by-step flowchart of step 500 in the method for preparing the fiber optic pressure sensor provided by the present invention. Implementation

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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. Example

[0044] like Figure 1 and 2 As shown, an optical fiber pressure sensor includes a single-mode optical fiber 1, a microcavity device 2, and a metal thin film 3. The microcavity device 2 has an optical microcavity 20 and a first port 21 and a second port 22 respectively connected to both ends of the optical microcavity 20. The first port 21 of the microcavity device 2 is connected to one end face of the single-mode optical fiber 1, and the second port 22 of the microcavity device 2 is connected to the metal thin film 3. A metal bonding layer 25 is formed on the second port 22 of the microcavity device 2 by vapor deposition. The metal thin film 3 is welded and fixed to the metal bonding layer 25 of the microcavity device 2 and suspended in front of the optical microcavity 20 of the microcavity device 2.

[0045] The fiber optic pressure sensor of this patent first forms a metal bonding layer 25 on the second port 22 of the microcavity device 2 using a vapor deposition method. Then, the metal thin film 3 is fixed to the metal bonding layer 25 of the microcavity device 2 by welding, so that the metal thin film 3 is suspended in front of the optical microcavity 20 of the microcavity device 2. Since the metal thin film 3 is fixed to the microcavity device 2 by welding to the metal bonding layer 25, the bonding is larger and stronger than that of the prior art where the metal thin film 3 is fixed to the microcavity device 2 by van der Waals forces. Moreover, since the metal bonding layer 25 is formed on the second port 22 of the microcavity device 2 by vapor deposition, in addition to van der Waals forces, there are also interaction forces generated by ionic bonds, covalent bonds, and metallic bonds formed during vapor deposition between the metal bonding layer 25 and the microcavity device 2, which greatly improves the firmness of the bonding between the metal thin film 3 and the microcavity device 2.

[0046] In this patent, the metal bonding layer 25 is only attached to the end face of the second port 22 of the microcavity device 2 (without covering the optical microcavity 20). The optical microcavity 20 between the end face of the single-mode fiber 1 and the metal thin film 3 constitutes an interference cavity 20'. The end face of the single-mode fiber 1, the interference cavity 20', and the metal thin film 3 together constitute a Fabry-Perot interferometer (FPI). External pressure causes the metal thin film 3 to deform, thereby changing the cavity length of the interference cavity 20'. By demodulating the cavity length change of the interference cavity 20', high-precision pressure sensing can be achieved.

[0047] The single-mode optical fiber 1 includes a core 11 and a cladding 12. The cladding 12 surrounds the circumference of the core 11. The refractive indices of the core 11 and the cladding 12 are different, which allows the optical signal to undergo total internal reflection at the junction of the core 11 and the cladding 12, and then propagate forward within the core 11.

[0048] In this embodiment, the inner diameter of the microcavity device 2 is equal to the diameter of the single-mode optical fiber 1, and the first port 21 of the microcavity device 2 is inserted and fixed to the end face of the single-mode optical fiber 1. The microcavity device 2 may be, but is not limited to, a ceramic ferrule, a quartz capillary tube, or a hollow tube.

[0049] Optical adhesive 4 is applied between the first port 21 of the microcavity device 2 and the outer wall of the single-mode optical fiber 1 for bonding and fixing, and sealant 5 is applied to the optical adhesive 4 for sealing and fixing.

[0050] The optical adhesive 4 is used for pre-fixing between the microcavity device 2 and the single-mode fiber 1, and the sealant 5 is used for sealing and fixing between the microcavity device 2 and the single-mode fiber 1. An inner bevel 23 is provided at the inner diameter of the first port 21 of the microcavity device 2, so that the inner diameter of the first port 21 gradually decreases from the outside to the inside. The optical adhesive 4 is applied between the inner bevel 23 of the first port 21 and the outer wall of the single-mode fiber 1, and is flush with the end face of the first port 21. The sealant 5 is applied between the end face of the first port 21, the optical adhesive 4, and the outer wall of the single-mode fiber 1.

[0051] The optical adhesive 4 is preferably, but not limited to, a UV-curable adhesive 4, and the sealant 5 is preferably, but not limited to, an epoxy resin.

[0052] An outer inclined surface 24 is provided at the outer diameter of the second port 22 of the microcavity device 2, so that the outer diameter of the second port 22 gradually increases from the outside to the inside. The metal solder layer 25 extends to the outer inclined surface 24 of the second port 22, and the metal film 3 also extends to the metal solder layer 25 located on the outer inclined surface 24 of the second port 22 for welding and fixation.

[0053] The metal thin film 3 includes a peripheral region and a central region, with the peripheral region surrounding the central region; the peripheral region is welded and fixed to the metal solder layer 25 of the microcavity device 2, and the central region is suspended in front of the optical microcavity 20 of the microcavity device 2.

[0054] The central region is mainly used to reflect optical signals. The reflected optical signals are coherent with another optical signal reflected from the end face of the single-mode fiber 1 to form an interference spectrum of reflected light. Under external pressure, the region undergoes deformation, which in turn causes the interference spectrum to drift and change.

[0055] Preferably, the metal solder layer 25 includes a chromium solder layer, and the metal thin film 3 includes a gold-tin alloy thin film. The chromium solder layer and the gold-tin alloy thin film have good welding performance and can be welded at a relatively low temperature to avoid damage to the device at high temperatures during welding.

[0056] The thickness of the metal solder layer 25 is between 36-44 nm, and the thickness of the metal thin film 3 is between 180-220 nm. Example

[0057] A method for fabricating an optical fiber pressure sensor, used to fabricate the optical fiber pressure sensor described in Example 1.

[0058] like Figure 3 As shown, the preparation method includes the following steps:

[0059] Step 100: Take a microcavity device 2, the microcavity device 2 having an optical microcavity 20 and a first port 21 and a second port 22 respectively connected to the two ends of the optical microcavity 20.

[0060] In step 100, the microcavity device 2 may be, but is not limited to, a ceramic ferrule, a quartz capillary, or a hollow tube.

[0061] Step 200: A metal solder layer 25 is formed on the second port 22 of the microcavity device 2 by vapor deposition.

[0062] In step 200, when the metal solder layer 25 is formed on the second port 22 of the microcavity device 2 by vapor deposition, the microcavity device 2 is fixed in the magnetron sputtering chamber of the deposition equipment, the second port 22 of the microcavity device 2 is placed facing the metal target, and the metal target is bombarded with a high-energy ion beam, causing the metal target to vaporize and overflow and sputter onto the second port 22 of the microcavity device 2 to form a metal solder layer 25 with a thickness between 36-44 nm.

[0063] Preferably, the metal solder layer 25 includes a chromium solder layer.

[0064] Step 300: A metal thin film 3 is formed on the metal solder layer 25 of the microcavity device 2 by wet transfer.

[0065] Specifically, such as Figure 4 As shown, in step 300, the step of transferring a metal thin film 3 onto the metal solder layer 25 of the microcavity device 2 by wet transfer is as follows:

[0066] Step 310: The metal thin film 3 is formed on the copper-based foil by vapor deposition.

[0067] In step 310, when forming the metal thin film 3 on the copper-based foil by vapor deposition, the copper-based foil is fixed in the magnetron sputtering chamber of the deposition equipment, with the surface of the copper-based foil facing the metal target. The metal target is bombarded with a high-energy ion beam, causing the metal target to vaporize and overflow and sputter onto the surface of the copper-based foil to form a metal thin film 3 with a thickness between 180-220 nm.

[0068] Step 320: Dissolve and corrode the copper-based foil using a sulfuric acid solution, so that the metal film 3 on the copper-based foil is transferred into the sulfuric acid solution.

[0069] In step 320, the concentration of the sulfuric acid solution is about 0.276 / ml. It is only necessary to cut a small piece of copper-based foil according to the size of the second port 22 of the microcavity device 2 and place it in the sulfuric acid solution for dissolution and corrosion. The metal film 3 on the cut copper-based foil should be able to cover the second port 22 of the microcavity device 2.

[0070] The metal film 3 should not be made of copper-based material to avoid corrosion by the sulfuric acid solution during the wet transfer process.

[0071] Step 330: Dilute and filter the sulfuric acid solution containing the transferred metal film 3 with deionized water, so that the metal film 3 in the sulfuric acid solution floats on the deionized water.

[0072] In step 330, the main purpose of diluting and filtering the sulfuric acid solution with deionized water is to clean the metal film 3, avoid the presence of copper-based foil and ferric chloride residue on the metal film 3, and reduce the pH of the solution.

[0073] Step 340: Slowly bring the second port 22 of the microcavity device 2 with the metal solder layer 25 close to the metal film 3 floating on the deionized water. After the metal solder layer 25 of the microcavity device 2 contacts the metal film 3, slowly pull it away so that the metal film 3 is transferred to the metal solder layer 25 of the microcavity device 2.

[0074] In step 340, the second port 22 of the microcavity device 2 should slowly approach the metal film 3 floating on the deionized water in a manner parallel to the metal film 3, so that the metal solder layer 25 of the microcavity device 2 can uniformly contact the metal film 3, thereby allowing the metal film 3 to uniformly transfer and adhere to the metal solder layer 25 of the microcavity device 2.

[0075] Step 350: Dry the metal film 3 on the microcavity device 2 so that the metal film 3 is bonded to the metal solder layer 25 of the microcavity device 2 and suspended in front of the optical microcavity 20 of the microcavity device 2.

[0076] In step 350, the metal film 3 is naturally dried at room temperature. During the drying process, due to the van der Waals forces, the outer region of the metal film 3 will adhere to the metal solder layer 25 of the microcavity device 2, while the middle region will be suspended in front of the optical microcavity 20 of the microcavity device 2.

[0077] Preferably, the metal thin film 3 comprises a gold-tin alloy thin film.

[0078] Step 400: Heat the microcavity device 2 to weld the metal solder layer 25 and the metal film 3 together.

[0079] In step 400, the microcavity device 2 is placed vertically in a vacuum sintering furnace, and the peak temperature of the vacuum sintering furnace is set to 310°C. The microcavity device 2 is heated and held at this temperature for 8 minutes to completely melt the metal film 3 and weld it to the metal weld layer 25. After cooling, a stable pressure-sensitive metal film 3 is formed, so that the metal film 3 is firmly bonded to the second port 22 of the microcavity device 2.

[0080] Since the metal thin film 3 is a gold-tin alloy thin film, it can be welded to the metal solder layer 25 with chromium solder layer at a relatively low temperature of 310°C, thus avoiding damage to the microcavity device 2 caused by the high temperature of welding.

[0081] Step 500: Connect the end face of a single-mode optical fiber 1 to the first port 21 of the microcavity device 2.

[0082] In step 500, the inner diameter of the microcavity device 2 is equal to the diameter of the single-mode optical fiber 1, and one end of the single-mode optical fiber 1 is inserted and fixed between the microcavity device 2 and the first port 21 of the microcavity device 2.

[0083] Specifically, such as Figure 5 As shown, in step 500, the step of inserting and fixing one end of the single-mode optical fiber 1 to the first port 21 of the microcavity device 2 is as follows:

[0084] Step 510: Cut one end face of the single-mode fiber 1 flat.

[0085] In step 510, the length of the single-mode fiber 1 is not particularly limited; the end face of the single-mode fiber 1 can be cut flat using a fiber optic cleaver.

[0086] Step 520: Insert the flattened end face of the single-mode fiber 1 into the optical microcavity 20 of the microcavity device 2 from the first port 21 of the microcavity device 2.

[0087] In step 520, the single-mode fiber 1 with its end face cut flat and the microcavity device 2 are first placed on a three-dimensional moving platform. Under the monitoring of a CCD, the three-dimensional moving platform is controlled to move the single-mode fiber 1 and the microcavity device 2 relative to each other to adjust the relative position between the single-mode fiber 1 and the first port 21 of the microcavity device 2. Then, the single-mode fiber 1 is inserted from the first port 21 of the microcavity device 2 into the optical microcavity 20 of the microcavity device 2.

[0088] Step 530: Couple the detection light into the single-mode fiber 1 from the other end face of the single-mode fiber 1, and collect the reflected light reflected back from the other end face of the single-mode fiber 1 to obtain the interference spectrum of the emitted light.

[0089] In step 530, the other end of the single-mode fiber 1 is connected to an optical detection system. The optical detection system couples a detection light into the single-mode fiber 1. When the detection light passes the end of the single-mode fiber 1, part of it is reflected back into the single-mode fiber 1. The detection light entering the optical microcavity 20 is reflected back into the single-mode fiber 1 when it reaches the surface of the metal thin film 3. The two reflected beams coherently interact on the photodetector of the optical detection system, thus obtaining the interference spectrum of the reflected light. The peak position of the interference spectrum is related to the distance between the single-mode fiber 1 and the metal thin film 3 (the cavity length of the interference cavity 20'). The distance between the single-mode fiber 1 and the metal thin film 3 can be calculated from the peak position of the interference spectrum.

[0090] Step 540: Adjust the insertion depth of the single-mode fiber 1 in the microcavity device 2 until the interference spectrum changes to the preset initial spectrum.

[0091] In step 540, as the insertion depth of the single-mode fiber 1 changes within the microcavity device 2, the distance between the end face of the single-mode fiber 1 and the metal thin film 3 also changes accordingly, thereby causing a drift change in the interference spectrum. When the interference spectrum is adjusted to a preset initial spectrum, the distance between the end face of the single-mode fiber 1 and the metal thin film 3 is the preset cavity length of the interference cavity 20'.

[0092] Step 550: Apply optical adhesive 4 between the first port 21 of the microcavity device 2 and the outer wall of the single-mode optical fiber 1 for bonding and fixation.

[0093] In step 550, the optical adhesive 4 is used to pre-fix the microcavity device 2 and the single-mode fiber 1 to prevent relative displacement between the microcavity device 2 and the single-mode fiber 1 from causing changes in the cavity length of the interference cavity 20'. An inner bevel 23 is provided at the inner diameter of the first port 21 of the microcavity device 2, so that the inner diameter of the first port 21 gradually decreases from the outside to the inside. The optical adhesive 4 is coated between the inner bevel 23 of the first port 21 and the outer wall of the single-mode fiber 1, and is flush with the end face of the first port 21.

[0094] The optical adhesive 4 is preferably, but not limited to, a UV-curable adhesive 4, which is cured by irradiating it with a UV curing lamp for 5 minutes.

[0095] Step 560: Apply sealant 5 to the optical adhesive 4 for sealing and fixation.

[0096] In step 560, the sealant 5 is used to seal and fix the microcavity device 2 and the single-mode optical fiber 1, preventing moisture from entering the interference cavity 20' through the gap between the microcavity device 2 and the single-mode optical fiber 1. The sealant 5 is applied between the end face of the first port 21, the optical adhesive 4, and the outer wall of the single-mode optical fiber 1.

[0097] The sealant 5 is preferably, but not limited to, epoxy resin. After application, it is left to stand at room temperature for 24 hours to allow it to fully cure.

[0098] 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 an optical fiber pressure sensor, characterized in that, Includes the following steps: Step 100: Take a microcavity device, the microcavity device having an optical microcavity and a first port and a second port respectively connected to the two ends of the optical microcavity; Step 200: A metal solder layer is formed on the second port of the microcavity device by vapor deposition; Step 300: A thin metal film is formed on the metal bonding layer of the microcavity device by wet transfer and suspended in front of the optical microcavity of the microcavity device; Step 400: Heat the microcavity device to weld the metal solder layer and the metal film together on the microcavity device; Step 500: Connect the end face of a single-mode optical fiber to the first port of the microcavity device; In step 300, the step of forming a thin metal film on the metal bonding layer of the microcavity device by wet transfer and suspending it in front of the optical microcavity of the microcavity device is as follows: Step 310: Form the metal thin film on a copper-based foil by vapor deposition; Step 320: Dissolve and etch the copper-based foil with a dilute nitric acid solution to transfer the metal film on the copper-based foil into the dilute nitric acid solution; Step 330: Dilute and filter the dilute nitric acid solution with the transferred metal film using deionized water, so that the metal film in the dilute nitric acid solution floats on the deionized water. Step 340: Slowly bring the second port of the microcavity device with the metal solder layer close to the metal film floating on the deionized water. After the metal solder layer of the microcavity device contacts the metal film, slowly pull it away to transfer the metal film onto the metal solder layer of the microcavity device. Step 350: Dry the metal film on the microcavity device to bond the metal film to the metal solder layer of the microcavity device and suspend it in front of the optical microcavity of the microcavity device.

2. The method for fabricating an optical fiber pressure sensor according to claim 1, characterized in that, The inner diameter of the microcavity device is equal to the diameter of the single-mode optical fiber. In step 500, one end of the single-mode optical fiber is inserted and fixed between the microcavity device and the first port.

3. The method for fabricating an optical fiber pressure sensor according to claim 2, characterized in that, The steps for connecting and fixing one end of the single-mode optical fiber to the first port of the microcavity device are as follows: Step 510: Cut one end face of the single-mode optical fiber flat; Step 520: Insert the flattened end face of the single-mode fiber into the optical microcavity of the microcavity device from the first port of the microcavity device; Step 530: Couple the detection light into the single-mode fiber from the other end face of the single-mode fiber, and collect the reflected light reflected back from the other end face of the single-mode fiber to obtain the interference spectrum of the reflected light; Step 540: Adjust the insertion depth of the single-mode fiber in the microcavity device until the interference spectrum changes to the preset initial spectrum; Step 550: Apply optical adhesive between the first port of the microcavity device and the outer wall of the single-mode optical fiber for bonding and fixation; Step 560: Apply sealant to the optical adhesive for sealing and fixation.

4. The method for fabricating an optical fiber pressure sensor according to claim 1, characterized in that, The metal solder layer includes a chromium solder layer, and the metal film includes a gold-tin alloy film.

5. A fiber optic pressure sensor, characterized in that, The optical fiber pressure sensor is obtained using the preparation method described in claim 1. The optical fiber pressure sensor includes a single-mode optical fiber, a microcavity device, and a metal thin film. The microcavity device has an optical microcavity and a first port and a second port respectively connected to both ends of the optical microcavity. The first port of the microcavity device is connected to one end face of the single-mode optical fiber, and the second port of the microcavity device is connected to the metal thin film. A metal bonding layer is formed on the second port of the microcavity device by vapor deposition. The metal thin film is welded and fixed to the metal bonding layer of the microcavity device and suspended in front of the optical microcavity of the microcavity device.

6. The fiber optic pressure sensor according to claim 5, characterized in that, The inner diameter of the microcavity device is equal to the diameter of the single-mode optical fiber, and the first port of the microcavity device is inserted and fixed to the end face of the single-mode optical fiber.

7. The fiber optic pressure sensor according to claim 6, characterized in that, Optical adhesive is applied between the first port of the microcavity device and the outer wall of the single-mode optical fiber for bonding and fixing, and sealant is applied to the optical adhesive for sealing and fixing.

8. The fiber optic pressure sensor according to claim 5, characterized in that, The metal thin film includes a peripheral region and a central region, with the peripheral region surrounding the central region; the peripheral region is welded and fixed to the metal solder layer of the microcavity device, and the central region is suspended in front of the optical microcavity of the microcavity device.

9. The fiber optic pressure sensor according to claim 5, characterized in that, The metal solder layer includes a chromium solder layer, and the metal film includes a gold-tin alloy film.

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