The Study Of Novel All-solid-state Fiber Optic High Temperature Sensors

In recent years,high temperature sensing technology using optic fiber has potential applications in the fields of aerospace,chemical metallurgy and so on for its unique physical characteristics.With the deepening of the research,optic fiber high temperature sensing technology has been gradually accepted by the market.The advantages such as all solid fiber structure,small size,easy production,high repeatability,high stability and immune to electromagnetic make those all solid state optic fiber temperature sensors a good choice for harsh industrial environment and aerospace.The fiber sensors based on Mach-Zehnder interferometers used in high temperature sensing own advantages such as high temperature sensitivity,stability and simple process.Optic fiber Bragg grating made by femtosecond laser can have large dynamic measurement range,high temperature resistance,etc.,and are of interest to the researchers.The main work of this paper is focused on all solid state optic fiber sensors,the interferometer based on multi-core fiber and the annealing characteristics of femtosecond induced fiber Bragg gratings.The main contents and results are summarized as follows:(1)Introduce the background of fiber optic temperature sensor based on Mach-Zehnder interferometer,analyze the temperature sensing theory of fiber interferometer from simple single mode-multi mode single-mode fiber structure,the temperature sensing theory of the fiber optic is also derivated.Using the core modes of the multi-core fiber and high order core modes of the multi-mode fiber,a type of high temperature sensitivity sensor is designed and implemented.The sensing setup on of the axial strain sensing is also studied and introduced.(2)The principle of fiber Bragg grating is introduced,the different writing technology and the temperature sensing principle of fiber grating are also investigated.The different theories of the refractive index modulation introduced by the femtosecond laser in the silica glass,the production process and the model analysis of the femtosecond platform based on our experiment platform are also introduced.(3)The high temperature sensing characteristics of the fiber Bragg grating made by point-by-point(PBP)writing technology using femtosecond laser in single mode fiber is analyzed.The refractive index modulation model of the femtosecond laser in the fiber core is deduced according to the resonant wavelength of the fiber grating at different temperatures,the response of the transmitted power and the femtosecond laser power distribution in the single-mode fiber core.The annealing characteristic prediction of the fiber Bragg grating written by the line-by-line(LBL)writing technology using femtosecond laser fiber is also consistent with the high temperature annealing reaction of the LBL written fiber Bragg grating.