The Research On Fiber Interferometric Sensors Based On Femtosecond Laser Inscription Technology

Optical fiber sensor has the advantages of small size,light weight,simple installation,no electromagnetic interference,intrinsic insulation,and chemical resistance,and can be stably used in many fields such as petroleum,chemical industry,transportation,energy,metallurgy,medicine and so on.In recent years,with the rapid development of femtosecond laser engraving technology,fiber optic devices have more possibilities.In this thesis,three types of interferometric fiber-optic sensors based on femtosecond laser engraving technology are mainly explored.The theoretical principles and preparation techniques of the three sensors are analyzed,and potential applications are explored.The details are as follows:1.The development history and the status quo of fiber optic sensors and femtosecond laser inscription are reviewed.The classification and advantages of fiber optic interference sensors are introduced.The principle,classification and several different preparation methods of Mach-Zehnder and Fabry-Perot interference are introduced in detail.the development of femtosecond laser inscription technology and the action mechanism of femtosecond laser inscription is introduced.2.An optical fiber in-line MZI based on femtosecond laser written waveguide in no-core fiber(NCF)is proposed.The interference principle and manufacturing process of this interferometer are explained in detail.The temperature,stress and refractive index responses are explored respectively,and the temperature and stress sensitivity were 33.48 pm/? and 2.62 pm/??,respectively.Samples with different distance of waveguides and coreless fiber-air interfaces exhibit different forms of refractive index response.3.A fiber in-line reflective MZI based on femtosecond laser inscribed tilted beam splitter in SMF is proposed.This chapter details the working principle and production process,and uses the Comsol tool to explore the variable of the tilt beam splitter angle.Research on its refractive index and temperature characteristics shows that the temperature and refractive index sensitivity are 0.03324 dB/? and-45.29 dB/RIU,respectively.4.A novel parallel structured fiber in-line interferometric device consisting of two sets of periodic internal mirrors which forms Fabry-Perot cavities with different cavity lengths is proposed.This device consists of two sets of constant-fiber FP cavities written by a femtosecond laser.This chapter mainly introduces the working principle of the cascade Fabry-Perot cavity structure in detail,and the Matlab simulation results of the interferometer.Then,the stress and high temperature characteristics were measured,and the sensitivity was 1 pm/?? and 16.91 pm/?,respectively.The three traditional fiber optic sensors presented in this paper have the advantages of strong mechanical strength,ease of manufacture,compact size and low cost.