Manufacturing method of refractive index sensor of external cavity type optical fiber Fabry-Perot interferometer

Abstract

The invention relates to a manufacturing method of a refractive index sensor of an external cavity type optical fiber Fabry-Perot interferometer, which utilizes a laser micromachining forming technology, can realize micron-sized accurate optical fiber machining, and can effectively improve the process consistency and long-term reliability of a final sensor product in cooperation with a fine adjustment displacement table, an electron microscope and a real-time imaging display system. Aiming at a hollow-core quartz tube optical fiber part in the sensor, the invention provides a novel open type Fabry-Perot interference cavity structure through laser processing, and the interaction between a light field and an external medium can be enhanced, so that the detection efficiency and sensitivity of the sensor on refractive index change are remarkably improved. Correspondingly, the invention further provides the sensor manufactured by the method and manufacturing equipment for executing the method, and the sensor and the manufacturing equipment have low cost and high universality and expansibility.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber interferometer sensor manufacturing, and particularly relates to a method for manufacturing an external cavity optical fiber Fabry-Perot interferometer refractive index sensor. Background Art

[0002] Currently, the size and overall performance of single-mode and multimode optical fibers used in Fabry-Perot (FP) interferometric sensors are approaching physical limits. Some of the latest existing technologies utilize hollow-core quartz tube fibers (HCFs). Their unique structure and high sensitivity to environmental changes further expand the design and manufacturing potential of these fiber-optic sensors. However, the current HCF fiber-optic sensor manufacturing process, which relies on polishing and tapering techniques, still suffers from widespread problems such as poor process consistency and low product performance robustness. Therefore, targeted optimization and improvement of the process and sensor structure design are necessary. Summary of the Invention

[0003] In view of this, and in response to the technical problems existing in this field, the present invention provides a method for manufacturing an external cavity fiber Fabry-Perot interferometer refractive index sensor, which specifically includes the following steps:

[0004] Step 1) Select a hollow-core quartz tube optical fiber according to the sensor design, remove the coating layer in the middle portion, wipe it with alcohol, and then perform laser processing using a femtosecond laser processing device in conjunction with a rotating fixture; the laser processing is performed in three steps, each time to form an opening in the middle portion, after which the hollow-core quartz tube optical fiber is axially rotated 120° and the next laser processing is performed; after the laser processing is completed, a hollow-core quartz tube optical fiber is obtained;

[0005] Step 2) using a fiber cleaver to cut the fiber at a specific distance from one end of the hole in the open hollow-core quartz tube optical fiber to form a smooth cut end surface;

[0006] Step 3) selecting a section of single-mode optical fiber 1, removing its coating, and wiping it with alcohol. Then, using an optical fiber cutter, cutting it to form a smooth cut end face. Using an optical fiber fusion splicer, aligning and fusion-splicing the cut end face of the open hollow-core quartz tube optical fiber and the cut end face of the single-mode optical fiber, thereby obtaining a section of single-mode optical fiber 1-hollow-core quartz tube optical fiber.

[0007] Step 4) Using a fiber cleaver, cut the single-mode optical fiber I-hollow-core quartz tube optical fiber at a specific distance from the other end of the opening to form a smooth cut end face;

[0008] Step 5) Select a section of single-mode optical fiber II, remove its coating, wipe it with alcohol, and then cut it using a fiber cleaver to form a flat cut end face; Use a fiber fusion splicer to align and fusion-splice the cut end face of the single-mode optical fiber I-hollow-core quartz tube optical fiber and the cut end face of the single-mode optical fiber II to obtain a section of single-mode optical fiber I-hollow-core quartz tube optical fiber-single-mode optical fiber II;

[0009] Step 6) Using a fiber cleaver, cut the single-mode fiber II at a specific distance from the fusion splice point between the single-mode fiber I and the hollow-core quartz tube fiber and the single-mode fiber II;

[0010] Step 7) placing the single-mode fiber I-hollow quartz tube fiber-single-mode fiber II into a reagent and connecting it to a demodulator, and performing a test to complete the manufacture of the external cavity fiber Fabry-Perot interferometer refractive index sensor.

[0011] Furthermore, in step 1), a hollow quartz tube optical fiber with an inner diameter of 75 μm, a cladding diameter of 125 μm, and a coating diameter of 150 μm is specifically selected; the processing length of the opening during each laser processing is designed to be 100±5 μm, the processing width is designed to be 25±5 μm, and the processing depth is designed to be 50 μm.

[0012] Furthermore, when the optical fiber is cut in step 2), step 4) and step 6), an XZ-axis fine-tuning stage is used to fix the optical fiber to be processed, and an electron microscope is used for real-time imaging display to observe the cutting process.

[0013] Furthermore, the single-mode optical fibers I and II in step 3) and step 5) are both single-mode optical fibers with a core diameter of 9 μm, a cladding diameter of 125 μm, a coating diameter of 250 μm, and a coating material of acrylic resin.

[0014] Correspondingly, the present invention also provides an external cavity optical fiber Fabry-Perot interferometer refractive index sensor manufactured using the above method.

[0015] Accordingly, the present invention also provides an external-cavity fiber Fabry-Perot interferometer refractive index sensor manufacturing device for executing the above method, which is composed of a femtosecond laser, an XZ-axis fine-tuning translation stage, an electron microscope, a fiber cutter, a fiber clamp, a high-stability platform, a fiber fusion splicer, and an imaging display system;

[0016] Among them, the high-stability platform is used to fix and support other components; the femtosecond laser is used to perform laser processing on hollow-core quartz tube optical fibers; the optical fiber cutter is used to cut hollow-core quartz tubes and single-mode optical fibers; a fiber clamp is set on the XZ-axis fine-tuning displacement stage to fix the optical fiber to be cut; the electron microscope is connected to the imaging display system to observe the optical fiber cutting process; the optical fiber fusion splicer is used to perform arc fusion splicing on single-mode optical fibers and hollow-core quartz tube optical fibers.

[0017] The above-mentioned method for manufacturing the external cavity fiber Fabry-Perot interferometer refractive index sensor provided by the present invention utilizes laser micromachining forming technology to achieve micron-level precision fiber processing, and in conjunction with a fine-tuning displacement stage, an electron microscope, and a real-time imaging display system, it can effectively improve the process consistency and long-term reliability of the final sensor product. For the hollow-core quartz tube optical fiber part in the sensor, the present invention provides a new open Fabry-Perot interferometer cavity structure through laser processing, which can enhance the interaction between the light field and the external medium, thereby significantly improving the sensor's detection efficiency and sensitivity to refractive index changes. Accordingly, the present invention also provides a sensor manufactured by the above method and a manufacturing device for executing the above method, which has low cost and high versatility and scalability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A flow chart of the method provided by the present invention;

[0019] Figure 2 A schematic diagram of the structure of a sensor manufactured using the method provided by the present invention;

[0020] Figure 3 A schematic diagram of a manufacturing device for performing the method provided by the present invention;

[0021] Figure 4 The figure is a diagram for verifying the effect of the sensor provided by the present invention in reagents with different refractive indices. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] The present invention provides a method for manufacturing an external cavity optical fiber Fabry-Perot interferometer refractive index sensor, such as Figure 1 As shown, the specific steps include:

[0024] Step 1) Select a hollow-core quartz tube optical fiber 2 according to the sensor design, remove the coating layer of the middle portion thereof, wipe it with alcohol, and then perform laser processing using a femtosecond laser processing device in conjunction with a rotating fixture; the laser processing is performed in three steps, each time to form an opening in the middle portion, after which the hollow-core quartz tube optical fiber is axially rotated 120° and the next laser processing is performed; after the laser processing is completed, a hollow-core quartz tube optical fiber is obtained;

[0025] Step 2) Using a fiber cleaver, cut the fiber at a distance of 500±10 μm from the left end of the hole in the open hollow-core quartz tube optical fiber to form a smooth cut end surface;

[0026] Step 3) Select a section of single-mode optical fiber I1, remove its coating, wipe it with alcohol, and then cut it with a fiber cleaver to form a flat cut end face; use a fiber fusion splicer to align and fusion-splice the cut end face of the open hollow-core quartz tube optical fiber and the cut end face of the single-mode optical fiber to obtain a section of single-mode optical fiber I-hollow-core quartz tube optical fiber;

[0027] Step 4) Using a fiber cleaver, cut the single-mode fiber I-hollow-core quartz tube fiber at a distance of 500±10 μm from the right end of the opening to form a smooth cut end face;

[0028] Step 5) Select a section of single-mode optical fiber II2, remove its coating, wipe it with alcohol, and then cut it with a fiber cleaver to form a flat cut end face; Use a fiber fusion splicer to align and fusion-splice the cut end face of the single-mode optical fiber I-hollow-core quartz tube optical fiber and the cut end face of the single-mode optical fiber II to obtain a section of single-mode optical fiber I-hollow-core quartz tube optical fiber-single-mode optical fiber II;

[0029] Step 6) Using a fiber cleaver, cut the single-mode fiber II at a specific distance from the fusion splice point between the single-mode fiber I and the hollow-core quartz tube fiber and the single-mode fiber II;

[0030] Step 7) placing the single-mode fiber I-hollow quartz tube fiber-single-mode fiber II into a reagent and connecting it to a demodulator, and performing a test to complete the manufacture of the external cavity fiber Fabry-Perot interferometer refractive index sensor.

[0031] In a preferred embodiment of the present invention, in step 1), a hollow-core quartz tube optical fiber with an inner diameter of 75 μm, a cladding diameter of 125 μm, and a coating diameter of 150 μm is specifically selected; the processing length of the opening during each laser processing is designed to be 100±5 μm, the processing width is designed to be 25±5 μm, and the processing depth is designed to be 50 μm.

[0032] In a preferred embodiment of the present invention, when performing optical fiber cutting in step 2), step 4) and step 6), an XZ-axis fine-tuning stage is used to fix the optical fiber to be processed, and an electron microscope is used for real-time imaging display to observe the cutting process.

[0033] In a preferred embodiment of the present invention, the single-mode optical fibers I and II in step 3) and step 5) are both single-mode optical fibers with a core diameter of 9 μm, a cladding diameter of 125 μm, a coating diameter of 250 μm, and a coating material of acrylic resin.

[0034] Accordingly, the present invention also provides an external cavity fiber Fabry-Perot interferometer refractive index sensor manufactured by the above method, the cross-sectional and three-dimensional structures of which are as follows: Figure 2 shown.

[0035] Accordingly, the present invention also provides an external cavity fiber Fabry-Perot interferometer refractive index sensor manufacturing device for executing the above method, such as Figure 3 As shown, it consists of a femtosecond laser (not shown), an XZ-axis fine-tuning translation stage 9, an electron microscope 6, a fiber cutter 7, a fiber clamp 8, a high-stability platform 4, a fiber fusion splicer 5, and an imaging display system 10;

[0036] Among them, the high-stability platform 4 is used to fix and support other components; the femtosecond laser is used to perform laser processing on the hollow-core quartz tube optical fiber 2; the optical fiber cutter 7 is used to cut the hollow-core quartz tube and single-mode optical fiber; the optical fiber clamp 8 is set on the XZ-axis fine-tuning displacement stage 9 to fix the optical fiber to be cut; the electron microscope 6 is connected to the imaging display system 10 to observe the optical fiber cutting process; the optical fiber fusion splicer 5 is used to perform arc fusion splicing on the single-mode optical fiber and the hollow-core quartz tube optical fiber.

[0037] Figure 4 The results of verification tests are shown in which the manufactured sensor was connected to a fiber optic interrogator and placed in reagent solutions with refractive indices of 1.4100 and 1.4117 RIU, respectively. It can be seen that the sensor exhibits obvious interference valley drift in both reagents, thus proving that it can provide good detection capabilities for solutions with different refractive indices.

[0038] It should be understood that the size of the serial numbers of the steps in the embodiment of the present invention does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0039] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing an external cavity fiber Fabry-Perot interferometer refractive index sensor, characterized in that: The specific steps include: Step 1) Select a hollow-core quartz tube optical fiber according to the sensor design, remove the coating layer in the middle portion, wipe it with alcohol, and then perform laser processing using a femtosecond laser processing device in conjunction with a rotating fixture; the laser processing is performed in three steps, each time to form an opening in the middle portion, after which the hollow-core quartz tube optical fiber is axially rotated 120° and the next laser processing is performed; after the laser processing is completed, a hollow-core quartz tube optical fiber is obtained; Step 2) using a fiber cleaver to cut the fiber at a specific distance from one end of the hole in the open hollow-core quartz tube optical fiber to form a smooth cut end surface; Step 3) selecting a section of single-mode optical fiber 1, removing its coating, and wiping it with alcohol. Then, using an optical fiber cutter, cutting it to form a smooth cut end face. Using an optical fiber fusion splicer, aligning and fusion-splicing the cut end face of the open hollow-core quartz tube optical fiber and the cut end face of the single-mode optical fiber, thereby obtaining a section of single-mode optical fiber 1-hollow-core quartz tube optical fiber. Step 4) Using a fiber cleaver, cut the single-mode optical fiber I-hollow-core quartz tube optical fiber at a specific distance from the other end of the opening to form a smooth cut end face; Step 5) Select a section of single-mode optical fiber II, remove its coating, wipe it with alcohol, and then cut it using a fiber cleaver to form a flat cut end face; Use a fiber fusion splicer to align and fusion-splice the cut end face of the single-mode optical fiber I-hollow-core quartz tube optical fiber and the cut end face of the single-mode optical fiber II to obtain a section of single-mode optical fiber I-hollow-core quartz tube optical fiber-single-mode optical fiber II; Step 6) Using a fiber cleaver, cut the single-mode fiber II at a specific distance from the fusion splice point between the single-mode fiber I and the hollow-core quartz tube fiber and the single-mode fiber II; Step 7) placing the single-mode fiber I-hollow quartz tube fiber-single-mode fiber II into a reagent and connecting it to a demodulator, and performing a test to complete the manufacture of the external cavity fiber Fabry-Perot interferometer refractive index sensor.

2. The method according to claim 1, wherein: In step 1), a hollow quartz tube optical fiber with an inner diameter of 75 μm, a cladding diameter of 125 μm, and a coating diameter of 150 μm is specifically selected; the processing length of the opening during each laser processing is designed to be 100±5 μm, the processing width is designed to be 25±5 μm, and the processing depth is designed to be 50 μm.

3. The method according to claim 1, wherein: When the optical fiber is cut in step 2), step 4) and step 6), the optical fiber to be processed is fixed by using an XZ axis fine adjustment stage, and the cutting process is observed by real-time imaging display using an electron microscope.

4. The method according to claim 1, wherein: The single-mode optical fibers I and II in step 3) and step 5) are both single-mode optical fibers with a core diameter of 9 μm, a cladding diameter of 125 μm, a coating diameter of 250 μm, and a coating material of acrylic resin.

5. An external cavity fiber Fabry-Perot interferometer refractive index sensor, characterized in that: The method according to any one of claims 1 to 4 is used for manufacturing.

6. A device for manufacturing an external-cavity fiber Fabry-Perot interferometer refractive index sensor for performing the method according to any one of claims 1 to 4, characterized in that: It consists of a femtosecond laser, an XZ-axis fine-tuning stage, an electron microscope, a fiber cutter, a fiber clamp, a high-stability platform, a fiber fusion splicer, and an imaging display system. Among them, the high-stability platform is used to fix and support other components; the femtosecond laser is used to perform laser processing on hollow-core quartz tube optical fibers; the optical fiber cutter is used to cut hollow-core quartz tubes and single-mode optical fibers; a fiber clamp is set on the XZ-axis fine-tuning displacement stage to fix the optical fiber to be cut; the electron microscope is connected to the imaging display system to observe the optical fiber cutting process; the optical fiber fusion splicer is used to perform arc fusion splicing on single-mode optical fibers and hollow-core quartz tube optical fibers.

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