Sandwich Structure Mach-Zehnder Interferometer Based On Photonic Crystal Fiber

This paper mainly introduces a Mach-Zehnder interferometer(MZI)based on sandwiched grapefruit photonic crystal fiber(PCF).The design of the interferometer's structure,working principle,fabrication process and application research of it are expounded.A reflective fiber-optic hydrogen sensor based on optical polarization modulation is introduced briefly,including applications in temperature and hydrogen response.The specific content of the article is arranged as follows;1.Firstly,introduce the research background and significance of this topic.The optical fiber MZI structure based on different structures has the advantages of compact structure,easy preparation,diverse structure,wide application range,and highly sensitivity.By citing specific research examples,the research and development status of this type of fiber interferometer is introduced.2.Secondly,introduce the design of interferometer's structure,working principle and fabrication process of the MZI based on sandwiched PCF.The interferometer is fused as the structure of SMF-MMF-PCF-MMF-SMF.The lengths of MMF and PCF are both 500-550?m.The first section of MMF plays a role of expanding the light,so that the light can enter the air holes and the glass fiber core of the PCF,forming an MZI structure.3.Thirdly,investigate the application of the interferometer in strain and temperature response.Then,based on the completed MZI,femtosecond laser micromachining technology is adopted to etch the tapered microchannel on the side of the PCF,allowing one of the holes in the fiber communicating with the external air.And the applications in the fields of gas pressure/gas refractive index(RI)and hydrogen concentration sensing are further explored,including the construction of test system devices,processing and analysis of spectral data.The results show the interferometer structure performs well,and their sensitivities are-8.57 nm/Mpa,-3244.06 nm/RIU,2.94 nm/%(vol%),respectively.The interferometer has the advantages of sturdy structure,easy preparation,and can be used for multi-field measurement.4.Fourthly,based on the results of temperature response and RI sensing in Part 3,propose a reflective fiber-optic hydrogen sensor based on optical polarization modulation,which converts a RI-modulated temperature sensor into a hydrogen sensor.The structure is composed of SMF and Panda type polarization-maintain fiber(PMF),and the side of PMF is coated with hydrogen-sensitive material.The design,working principle and preparation method of the sensor are introduced,also the temperature and hydrogen concentration sensing experiments are conducted.The temperature sensitivity and hydrogen sensitivity are-1.46 nm/? and-18.038 nm/%,respectively.The response speed,repeatability,and detection limit of the hydrogen sensor were tested,and the results show that the device performs well.5.Finally,summarize the research content of this thesis,proposes corresponding solutions to the deficiencies found in the process,and put forward the future application of fiber optic devices in the sensing field.This paper proposes two types of optical fiber devices,which have advantages such as compact and sturdy structure,simple preparation,anti-electromagnetic interference ability,high stability,etc.The research results show that they have good application prospects in the field of optical fiber sensing.