Research On Fiber Optic Sensor Based On Mach-zehnder Interference

Due to their small size,anti-electromagnetic interference,high sensitivity and specificity,fiber optic was widely concerned and it had been widely employed in the field of daily life and work.This dissertation uses taper,spherical,peanut-shaped three structures based on the Mach-Zehnder interference principle,respectively.The thin-core single-mode fiber and polarization-maintaining fiber are used to construct different types of fiber optic sensors.This dissertation introduces the manufacturing method and sensing principle of each kind of optical fiber sensor and analyzes the measurement of physical parameters.The main contents of this dissertation are as follows:1.The background and application of optical fiber sensor are introduced,and the fiber optic sensors are classified and explained.The basic structure and types of common optical fiber sensors based on Mach-Zehnder interferometer are described.The physical parameters such as the refractive index,temperature,strain and other related are theoretically analized.And the current double-parameter research reports combines with the sensitivity coefficient matrix are summarized to achieve simultaneous measurement of the physical two parameters.2.The fiber sensor for simultaneously measuring refractive index and temperature are proposed.The fiber sensor is constructed by waist-enlarged thin-core single-mode fiber and the polarization-maintaining fiber,respectively.Experiment results indicate that the sensitivity to the refractive index in the range of 1.3455 to 1.4025 is 257.53nm/RIU and the sensitivity to the temperature in the range of 20 to 80 ? is 19.30pm/?,respectively.For the polarization-maintaining optical fiber sensor,the sensitivity to the refractive index in the range of 1.3476 to 1.4105 is-35.0502 nm/RIU and the sensitivity to the temperature in the range of 25 to 75 ? is 145.60 pm/?,respectively.3.The fiber sensor for simultaneously measuring temperature and strain are proposed.The fiber sensor is constructed by sandwiching a thin-core single-mode fiber and polarization-maintaining fiber between two spherical-shaped fibers,respectively.Experiment results indicate that the thin-core single-mode optical fiber sensor,the sensitivity to the temperature in the range of 25 to 85 ? is 53.86 pm/?and the sensitivity to the strain in the range of 0 to 1048.95 ?? is-1.39 pm/??,respectively.For the polarization-maintaining optical fiber sensor,the sensitivity to the temperature in the range of 25 to 70 ? is 93.32 pm/? and the sensitivity to the strain in the range of 0 to 1764 ?? is-0.9445 pm/??,respectively.4.The peanut type optical fiber sensor for simultaneously measuring temperature and refractive index,temperature and strain are proposed,respectively.Experiment results indicate that the thin-core single-mode optical fiber sensor,the sensitivity to the temperature in the range of 25 to 80 ? is 24.47 pm/? and the sensitivity to the refractive index in the range of 1.3415 to 1.4012 is 84.60 nm/RIU.For the polarization maintaining optical fiber sensor,the sensitivity to the temperature in the range of 25 to75 ? is 31.74 pm/? and the sensitivity to the strain in the range of 0 to 1568 ?? is-2.22 pm/??,respectively.