Pressure sensor based on a sapphire optical fiber microbubble structure and methods of making and using

Abstract

The application provides a pressure sensor based on a sapphire optical fiber micro-bubble structure and a preparation and use method, first grinding a sapphire optical fiber end face to have an optical level roughness, then etching the optical fiber end face to form a hollow cavity structure by using a femtosecond laser water breakdown method, and finally adopting an arc discharge technology to discharge the sapphire optical fiber end face hollow cavity structure for multiple times to make it collapse inward to form a closed micro-bubble structure cavity for sensing pressure, and the micro-bubble cavity is a Fabry-Perot interference cavity. When the pressure changes, the bubble wall surface compresses to the cavity, and the pressure value of the environment can be calculated by measuring the cavity length change. The technical scheme provided by the application produces a high-temperature-resistant pressure sensor based on a sapphire optical fiber micro-bubble structure, the sapphire optical fiber has high temperature resistance, meanwhile, the micro-bubble structure preparation process is simple, has high reliability, and can avoid electromagnetic interference.

Description

Technical Field

[0001] This invention relates to the field of fiber optic pressure sensor technology, and in particular to a pressure sensor based on a sapphire fiber microbubble structure and its preparation and use methods. Background Technology

[0002] In aerospace engine performance research, pressure measurement under high-temperature environments is a critical and complex task. Traditional electronic pressure sensors suffer from reliability and stability issues in high-temperature, high-pressure, and electromagnetic interference environments. In recent years, with the development of fiber optic sensing technology, quartz fiber-based pressure sensors have been gradually applied to aerospace engine performance testing. Although they outperform electronic sensors in terms of temperature resistance, they face problems such as sensor structure damage or signal attenuation in extreme high-temperature environments such as 1400K, making them unsuitable for long-term high-temperature and transient high-temperature environments. Summary of the Invention

[0003] To address the problem of poor temperature resistance of traditional quartz optical fiber materials, this invention proposes a pressure sensor based on sapphire optical fiber microbubble structure, along with its preparation and application method. The method is simple, and the resulting sensor has a streamlined structure, high dynamic sensitivity, and high temperature resistance and reliability, which can overcome the application limitations of existing technologies in high-temperature environments.

[0004] To address the aforementioned technical problems, this invention provides a method for fabricating a pressure sensor based on a sapphire fiber microbubble structure, comprising the following steps:

[0005] Step 1: Mechanically grind the end face of the sapphire fiber to obtain a flat sapphire fiber end face with optical-grade roughness.

[0006] Step 2: Place the end-face treated sapphire fiber in the fiber fixture and use femtosecond laser water breakdown method to etch the fiber end face to form a hollow cavity structure.

[0007] Step 3: Place the sapphire optical fiber with a hollow cavity structure into the optical fiber fusion splicer. Use arc discharge technology to discharge the hollow cavity structure at the end face of the sapphire optical fiber multiple times, causing it to collapse inward to form a closed microbubble structure. This microbubble structure belongs to the fiber Fabry-Perot interferometer cavity structure and is used to sense pressure changes.

[0008] In a preferred embodiment: the specific method of mechanically grinding the end face of the sapphire optical fiber in step 1 is as follows: using a bare optical fiber grinder and an electron microscope for real-time observation, coarse grinding of the optical fiber to remove fiber edge breakage, semi-fine grinding, fine grinding, and polishing to obtain a good, flat surface with optical-grade roughness.

[0009] In a preferred embodiment: step 2 specifically includes the following steps:

[0010] Step 2.1: Place the sapphire optical fiber after mechanical grinding in the optical fiber fixture, so that the ground end face of the optical fiber is completely submerged in water, and the water level is higher than the end face of the optical fiber. Finally, cover the fixture with a transparent cover glass.

[0011] Step 2.2: Use a femtosecond laser to focus on the processing surface and control the displacement stage to move and process the corresponding pattern to obtain the hollow cavity structure of the sapphire fiber end face.

[0012] In a preferred embodiment: the specific method for fabricating microbubbles by repeatedly discharging the hollow cavity structure of the sapphire fiber end face using the fiber fusion splicer is as follows: the prepared hollow cavity structure of the sapphire end face is placed in the fiber fusion splicer, and the sapphire end face hollow cavity structure is collapsed by controlling the advance distance of the fusion splicer, the discharge intensity and the discharge time, thereby forming a closed microbubble structure.

[0013] The present invention further provides a sapphire fiber microbubble pressure sensor obtained by the preparation method of the pressure sensor based on the sapphire fiber microbubble structure, comprising a sapphire fiber body and a pressure sensing part.

[0014] In a preferred embodiment: the pressure sensing unit is disposed at the end along the length direction of the sapphire fiber body, and its bottom is coaxially fixed to the end of the sapphire fiber body; the pressure sensing unit is a Fabry-Perot interferometer cavity.

[0015] The present invention also provides a method for using the pressure sensor based on the sapphire fiber microbubble, characterized in that: when the environmental pressure changes, causing a change in the cavity length of the Fabry-Perot interferometer, the spatial pressure value can be inferred by measuring the amount of cavity length change.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0017] This invention provides a pressure sensor based on a sapphire fiber microbubble structure and its fabrication method, which solves the problems of complex fabrication process and limited application in high-temperature environments of existing fiber optic sensing structures. The invention has a simple structure, reasonable design, and high dynamic sensitivity. The sapphire fiber used has extremely high high-temperature resistance. At the same time, the microbubble structure fabrication has high reliability and can avoid electromagnetic interference, which is beneficial to the expansion and promotion of the application scope of fiber optic sensing technology. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall shape of the sapphire fiber microbubble pressure sensor of the present invention;

[0019] Figure 2 This is a schematic diagram of the morphology of the sapphire fiber end-face processing structure of the present invention.

[0020] Figure 3 This is a schematic diagram of the sapphire fiber end face water breakdown etching apparatus of the present invention;

[0021] Figure 4 This is a schematic diagram of the hollow cavity structure and end face morphology of the sapphire optical fiber of the present invention.

[0022] Figure 5 This is a schematic diagram showing the position of the sapphire optical fiber hollow cavity structure of the present invention placed in the fusion splicer;

[0023] Figure 6 This is a flowchart illustrating the fabrication process of a pressure sensor based on sapphire fiber microbubbles according to the present invention. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0027] refer to Figure 1-6 The pressure sensor based on sapphire fiber microbubbles according to the embodiments of the present invention includes a sapphire fiber body and a pressure sensing part; the pressure sensing part is disposed at the end along the length direction of the sapphire fiber body, and its bottom is coaxially fixed to the end of the sapphire fiber body; the pressure sensing part is a Fabry-Perot interferometer cavity.

[0028] It is important to emphasize the fabrication method of the pressure sensor based on sapphire fiber microbubbles. This method involves etching a hollow cavity structure on the end face of a sapphire fiber, and then using arc discharge technology to form a closed microbubble interference cavity. Environmental pressure is measured by detecting changes in the cavity length of a Fabry-Perot (FP) interferometer. The specific steps are as follows:

[0029] Step 1: First, use 9μm roughness abrasive paper on a bare fiber polishing machine to roughen the end face of the sapphire fiber 10, removing chipped edges and defects. Then, use 5μm and 1μm roughness abrasive paper for semi-finishing and finishing, respectively, to ensure the fiber end face is flat. Finally, use 0.1μm polishing paper for polishing to obtain an optical-grade fiber end face. The polishing process is monitored in real-time using a microscope. The fiber appearance after polishing is as follows. Figure 2 As shown.

[0030] Step 2: As Figure 3 As shown, the sapphire fiber 10, after end-face processing, is placed in the fiber fixture 20, water 21 is added, ensuring the liquid level is higher than the sapphire fiber end face, and finally a transparent cover glass 22 is placed on top to prevent water from overflowing from the fixture groove. The femtosecond laser focus is controlled to act on the processed end face. When the femtosecond laser acts on the water, it accelerates the water flow, enabling effective processing of the fiber end face. Furthermore, the water can clean away any debris generated, preventing it from accumulating at the processing location and affecting laser efficiency. The displacement stage is controlled to move to the corresponding processing position to obtain the shape of the hollow cavity structure 11 in the sapphire fiber end face. The final processed end face morphology and structure are shown below. Figure 4 As shown.

[0031] Step 3: As Figure 5 As shown, the sapphire fiber is moved to the position of the fiber fusion splicer electrode 31 by the stepper motor on the fiber fusion splicer 30. Then, it is first cleaned by a short-term low-power discharge. Next, the thermal fusion parameters are set to discharge the hollow cavity structure of the sapphire fiber. The discharge is heated multiple times to make it form a semi-molten state. Due to the existence of the hollow cavity structure, the end face of the fiber collapses inward to form a closed microbubble 12. The microbubble constitutes the fiber Fabry-Perot interference cavity structure.

[0032] Furthermore, based on the manufacturing process of the sapphire fiber microbubble pressure sensor, it is known that when the environmental pressure changes, causing a change in the cavity length of the Fabry-Perot interferometer, the user can calculate and infer the spatial pressure value by measuring the change in cavity length.

[0033] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A method for fabricating a pressure sensor based on sapphire fiber microbubbles, characterized in that, Includes the following steps: Step 1: Mechanically grind the end face of the sapphire fiber to obtain a flat sapphire fiber end face with optical-grade roughness. Step 2: Place the end-face treated sapphire fiber in the fiber fixture and use femtosecond laser water breakdown method to etch the fiber end face to form a hollow cavity structure. Step 3: Place the sapphire optical fiber with a hollow cavity structure into the fiber optic fusion splicer. Use arc discharge technology to repeatedly discharge the hollow cavity structure of the sapphire end face, causing it to collapse inward and form a closed microbubble structure. This microbubble structure belongs to the fiber Fabry-Perot interferometer cavity structure and is used to sense pressure changes. The specific method for mechanically grinding the sapphire optical fiber end face as described in Step 1 is as follows: Use a bare fiber grinder and an electron microscope for real-time observation. Rough grinding removes fiber chipping, followed by semi-fine grinding, fine grinding, and polishing to obtain a smooth surface with optical-grade roughness. Step 2 specifically includes the following steps: Step 2.1: Place the sapphire optical fiber after mechanical grinding in the optical fiber fixture, so that the ground end face of the optical fiber is completely submerged in water, and the water level is higher than the end face of the optical fiber. Finally, cover the fixture with a transparent cover glass. Step 2.2: Focus a femtosecond laser on the processing surface and control the displacement stage to process the corresponding pattern to obtain the hollow cavity structure of the sapphire fiber end face; the specific method for making microbubbles by repeatedly discharging the hollow cavity structure of the sapphire fiber end face according to the fiber fusion splicer described in Step 3 is as follows: place the prepared hollow cavity structure of the sapphire fiber end face in the fiber fusion splicer, and by controlling the advance distance of the fusion splicer, the discharge intensity and the discharge time, the hollow cavity structure of the sapphire end face will collapse to form a closed microbubble structure.

2. A sapphire fiber microbubble pressure sensor prepared by the preparation method described in claim 1, characterized in that; It includes a sapphire optical fiber body and a pressure sensing unit; the pressure sensing unit is disposed at the end along the length direction of the sapphire optical fiber body, and its bottom is coaxially fixed to the end of the sapphire optical fiber body. The pressure sensing unit is a Fabry-Perot interferometer cavity.

3. The method of using the sapphire fiber microbubble pressure sensor according to claim 2, characterized in that: When changes in environmental pressure cause changes in the cavity length of the Fabry-Perot interferometer, the spatial pressure value can be inferred by measuring the amount of change in cavity length.

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