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CN-121994285-A - Multi-core optical fiber end face hydrogen and air pressure decoupling sensor and preparation method thereof

CN121994285ACN 121994285 ACN121994285 ACN 121994285ACN-121994285-A

Abstract

The invention belongs to the technical field of optical fiber sensing, and particularly relates to a multi-core optical fiber end face hydrogen and air pressure decoupling sensor and a preparation method thereof. The sensor comprises a multi-core optical fiber, a micro-cantilever beam and a closed cavity structure which are positioned on the end face of the multi-core optical fiber, wherein the micro-cantilever beam and the closed cavity structure are directly printed on the end face of the optical fiber through a femtosecond laser two-photon polymerization technology, a palladium film positioned on the upper surface of the micro-structure is plated through an electron beam evaporation technology, so that the micro-cantilever Liang Jubei is hydrogen-sensitive, and the cavity is closed by ultraviolet glue. The invention can realize simultaneous measurement of hydrogen and air pressure in the scenes of micro-channels, air chambers, storage air tanks and the like, has the characteristics of small size, easy integration, high sensitivity, reliability and safety, and can realize a reliable hydrogen monitoring function in the environment of pressure fluctuation.

Inventors

  • XIAO LIMIN
  • SUN JIE
  • WANG CAOYUAN
  • XIONG CONG

Assignees

  • 复旦大学

Dates

Publication Date
20260508
Application Date
20260203

Claims (6)

  1. 1. A multi-core fiber end face hydrogen and gas pressure decoupling sensor, comprising: the multi-core optical fiber (1), namely a single optical fiber, comprises a plurality of parallel fiber cores, and: The cavity (21) is positioned at the end face right above a certain fiber core, a closed cavity is formed by curing ultraviolet glue, the top of the cavity is provided with a sensing film (25), and the sensing film (25) is used for shielding light emitted from the fiber core; The inclined shielding cover (26) is positioned above the cavity (21) and connected with the cavity (21) through peripheral support columns (24), and the inclined shielding cover (26) is used for shielding palladium metal in the preparation process so as to prevent the palladium metal from depositing on a top film of the cavity (21), so that the sensor is crossly sensitive, and the influence of multi-beam interference is reduced so as to facilitate spectrum demodulation; The micro-cantilever beam (31) is provided with hydrogen sensitivity, one end of the micro-cantilever beam is connected with the low side of the inclined shielding cover (26), the other end of the micro-cantilever beam is suspended and positioned on the upper end surface of the other fiber core, light emitted from the fiber core is shielded, and the end surface of the fiber core and the lower surface of the micro-cantilever beam are used as two-sided reflectors to form an air medium Fabry-Perot interferometer; The palladium membrane (32) is covered on the upper surfaces of the inclined shielding cover (26) and the micro-cantilever (31); The side surface of the cavity (21) is provided with a communicated pipeline (23) for facilitating the developer to clean unpolymerized photoresist in the cavity and subsequent ultraviolet glue sealing.
  2. 2. The multi-core fiber end face hydrogen and gas pressure decoupling sensor of claim 1, wherein: the cavity (21), the inclined shielding cover (26) and the micro cantilever (31) are directly printed on the end face of the optical fiber through femtosecond laser two-photon polymerization; The palladium film (32) is positioned on the upper surfaces of the micro-cantilever and the shielding cover and is formed by plating through an electron beam evaporation technology.
  3. 3. The multi-core fiber end face hydrogen and gas pressure decoupling sensor of claim 1, wherein: the shape of the cavity (21) is hollow cylinder or prismatic; the palladium membrane (32) is plated on the upper surfaces of the micro-cantilever and the shielding cover, and the shape of the palladium membrane is consistent with that of the micro-cantilever and the shielding cover.
  4. 4. The multi-core fiber end face hydrogen and gas pressure decoupling sensor of claim 1, wherein: the number of the cores of the multi-core optical fiber (1) is N, and N is more than or equal to 2; The height of the cavity (21) is 5-200 mu m, the wall thickness is 2-10 mu m, and the thickness of the top film (25) is 0.1-5 mu m; the length of the side pipeline (23) of the cavity (21) is 5-30 mu m, and the pipe diameter is 2-20 mu m; The thickness of the shielding cover (26) is 1-10 mu m, and the inclination angle is 8-60 degrees.
  5. 5. The multi-core fiber end face hydrogen and gas pressure decoupling sensor of claim 1, wherein: The length of the micro-cantilever beam (31) is 5-50 mu m, the width of the micro-cantilever beam is 2-50 mu m, and the thickness of the micro-cantilever beam is less than 20 mu m; the palladium membrane (32) has a thickness of less than 1 μm.
  6. 6. The method for preparing the multi-core fiber end face hydrogen and air pressure decoupling sensor as claimed in any one of claims 1 to 5, wherein the method comprises the following specific steps: (1) According to the core diameter, core distribution and core spacing of the multi-core optical fiber, a matched cavity is designed in consideration of the adhesion firmness of a polymer structure and the end face of the optical fiber, and a matched micro cantilever is designed in consideration of the mechanical properties of polymer materials; (2) Cutting the multi-core optical fiber into a flat by using a cutting knife, immersing the end face of the optical fiber in photoresist, assembling the optical fiber to a femtosecond laser processing platform, observing CCD imaging, locating the end face of the optical fiber by using a moving platform, selecting a proper processing starting position, focusing the femtosecond laser by using an oil immersion objective lens, and processing the micro cantilever beam and the cavity designed in the step (1) by matching with a high-precision displacement platform; (3) Removing unpolymerized photoresist from the sample processed in the step (2) by using a developing solution to obtain a polymerized micro-cantilever and cavity structure, and performing polymerization reinforcement by using an ultraviolet lamp; (4) Placing the sample solidified in the step (3) and a single-mode fiber with a small amount of ultraviolet glue on one end face on a precise displacement platform, observing CCD imaging, slowly moving the platform to enable a pipeline on the side wall of the cavity to be immersed in the ultraviolet glue, and immediately separating the two optical fibers once the glue flows into and seals the pipeline so as to prevent the glue from continuously flowing into the cavity; (5) And (3) plating the palladium film on the upper surface of the micro-cantilever beam on the sample filled in the step (4) by utilizing an electron beam evaporation technology, so that the sample has hydrogen sensitivity.

Description

Multi-core optical fiber end face hydrogen and air pressure decoupling sensor and preparation method thereof Technical Field The invention belongs to the technical field of optical fiber sensing, and particularly relates to a multi-core optical fiber end face hydrogen and air pressure decoupling sensor and a preparation method thereof. Background Optical fiber sensors are widely researched and valued in the technical field of sensing and gradually become the research focus of the field due to the unique advantages of electromagnetic interference resistance, chemical corrosion resistance, slim volume, cost economy and the like. Among various optical fiber sensors, the single-core optical fiber sensor has the most perfect technical development, and has been successfully developed and applied to various fields such as high-temperature environment monitoring, gas detection, biosensing and the like. The sensor has good biocompatibility, arc-free characteristic and high sensitive detection capability, and fully shows great development potential of the optical fiber technology in the biomedical field and in sensing application under extreme working conditions. However, the traditional single-core optical fiber sensor has the outstanding limitations that on one hand, the detection function is mainly concentrated on single physical or chemical parameters, and is difficult to adapt to the actual requirement of synchronously detecting various parameters in a complex environment, and on the other hand, the change of other irrelevant parameters in the environment easily causes interference errors to the measurement process, so that the accuracy and precision of the sensor are limited to a great extent. In order to improve the current situation, a part of researches are carried out by preparing a plurality of sensing elements such as fiber bragg gratings, interferometers and the like in the fiber core of a single-core optical fiber, so as to try to realize the targets of multi-parameter sensing and parameter compensation, but the method is extremely easy to cause signal crosstalk phenomenon among the sensing elements, and meanwhile, extra transmission loss is introduced, so that the overall working performance of the sensor is finally reduced. Besides, a part of researches adopt an optical fiber bundle mode to realize multi-parameter discrete detection, and the scheme can enlarge the measurement dimension to a certain extent, but can enlarge the volume of a sensing device, and meanwhile, the structure of the whole sensing system becomes more complex, so that popularization and use of the sensing system in miniaturized and integrated application scenes are limited. The multi-core optical fiber provides an effective way for solving the problems, a plurality of mutually independent fiber cores are integrated in one optical fiber to form a multi-channel optical transmission path, and the multi-core optical fiber has the characteristic of compact structure and further expands the integration space and dimension of an optical sensing element. The existing scientific research workers successfully realize accurate sensing of parameters such as multi-directional bending, torsion angles, acceleration and the like by writing fiber grating structures in each independent fiber core of the multi-core fiber, and the scientific research workers additionally have the capability of identifying parameter directions on the basis of realizing accurate measurement of parameter values; in addition, by integrating optical sensing elements with different types and different materials on different fiber cores, the measuring range of the sensor can be further expanded from single parameter to multi-parameter synchronous detection, wherein synchronous measurement of temperature and humidity is the most typical application case, and the improvement remarkably enhances the adaptability of the optical fiber sensor to complex environments. Hydrogen is used as a clean gas, has medical use of antioxidation and anti-inflammatory and high-efficiency energy use, and has extremely high application value. However, the inherent property of hydrogen, which is flammable and explosive, causes a greater safety risk in the transportation, storage and practical application processes, which also puts more strict requirements on the detection technology. The optical fiber is used as an optical signal transmission waveguide, has the remarkable advantage of no electric arc generation, can realize detection on the premise of not contacting with the detected gas, and is an ideal device for detecting flammable and explosive gases such as hydrogen. In recent years, various hydrogen sensors based on optical fibers are widely researched and developed, but most of the existing research results are focused on the detection of a single parameter, namely the hydrogen concentration, and the actual detection requirements under complex application scenes are difficult to meet. Parti