Research On The Fiber-Optic Hydrogen Sensor Based On Extrinsic Fabry-Perot Interferometer

As a renewable and clean energy source,hydrogen has a wide range of applications.However,hydrogen is a flammable and explosive gas that can explode with a 4%concentration in the environments.In order to avoid hydrogen explosion accidents,it is of great significance to study hydrogen sensors that are safe,reliable,high sensitivity and able to monitor remotely.Fiber optic sensors are ideal for hydrogen monitoring due to their small size,high sensitivity,high safety and remote monitoring.Based on the understanding of various types of fiber-optic hydrogen sensors and the existing technology of the laboratory,this paper proposes a fiber-optic Fabry-Perot(F-P)hydrogen sensor with fast response and simple structure.For the proposed sensor,this thesis focus on the following work:Firstly,the research background of fiber-optic hydrogen sensors and the state-of-art of various types of sensors are introduced.The advantages and disadvantages of various fiber-optic hydrogen sensors are analyzed.The main hydrogen-sensitive materials are also introduced.Secondly,the theory of interference and F-P interferometer are described.Three types of F-P sensors are briefly summarized and the sensing mechanism of palladium is analyzed.Thirdly,based on the investigation of palladium's metal characteristics,the theoretical model of the sensing system is established.The relationship between response time and film thickness is simulated and the response time and sensitivity of the sensor are determined.Finally,based on the above theoretical analysis and numerical simulation,fiber-optic F-P hydrogen sensors based on C-type ceramic ferrule sleeves are designed and fabricated,and the detailed experimental research on its sensing performance is carried out.The experimental results show that the sensitivity of the sensor relate to the thickness of the palladium film.The thicker the thickness,the higher the sensitivity.For a palladium film with a thickness of 100?m,the sensitivity of the sensor can reach 1.42 nm/%.The resolution of the cavity length is about 0.16 nm corresponding to a resolution of 2000 ppm for the hydrogen concentration.The hydrogen diffusion coefficient in the palladium film is calculated to be about 11.3?m/s~2,and the response time of the proposed sensor is within 10 minutes.In addition,the temperature characteristics of the sensor are tested.The results show that the sensor has a temperature sensitivity of 3.74nm/°C.With temperature compensation,the effect of temperature can be eliminated.