Research On Optical Fiber Hydrogen Sensing Technologies Based On Femtosecond Laser Micro-machining

With the wide use of hydrogen in the areas of energy and power, food hygiene, military defense and so on, hydrogen leakage is a key issue for safety problem, and intensive research activities have been carried out for hydrogen leakage monitoring. The traditional hydrogen sensor is usually based on electrochemical way to realize detection, there will be the potential risk of explosion. Optical fiber hydrogen sensor has the advantages of intrinsic safety, immune to electromagnetic interference, high sensitivity, stability, high reliability, corrosion resisting, small size and so on, and is especially suitable for all kinds of harsh environments. In view of the problem of Complicated process of traditional interferometric fiber optic sensor, this paper proposes a solution for hydrogen detection using of femtosecond laser micro processing combined with magnetron sputtering deposition technology. In this paper, the main research work is as follows:(1) Analyzed the basic theory of beam propagation method, then optical properties simulation of optical fiber Mach-Zehnder microstructure with optical waveguide simulation software RSoft are conducted. Simulated the spectral features of microstructure under different conditions of parameters (shape, size, refractive index and so on), which can be used as reference for the design and manufacture of microstructure.(2) Researched optical fiber hydrogen sensor based on the Mach Zehnder interference principle, and the basic principle and fabricated method are analyzed in detail. The response of the sensor under different concentrations of hydrogen are studied with experiments. The sensitivity of the sensor (L=40μm, dfilm=110nm) is～0.155nm/%, the response time is about90s with the the change of hydrogen concentrations per4%, and the sensor has well repeatability. Experiments show that the sensor has high sensitivity, and has the advantages of easily fabricated, well repeatability, small size and so on..(3) In view of the cross-sensitivity of hydrogen concentration to temperature of based on a single Mach Zehnder interferometer optical fiber hydrogen sensor, put forward the hydrogen concentration detection scheme of combination of Mach-Zehnder interferometer and FBG. Introduced the basic principle of the scheme and the preparation method of the sensor in detail. Studied the response of the sensor under the temperature and hydrogen concentration changing at the same time with experiment. It turned out that temperature compensation can be realized, measurements of temperature and hydrogen concentration are realized at the same time.The innovation of this paper is the research theory and method for detection of hydrogen concentration by combining femtosecond micro-machining with magnetron sputtering deposition technology.