Research On Optical Fiber Sensor Based On Optical Fiber Microcavity

Recent years, due to their unique advantages, such as small size, light weight, low transmission loss, corrosion resistant ability, high-temperature survivability, high sensitivity, immunity to electromagnetic interference, optical fiber sensors have been widely investigated and used in health monitoring of building, temperature monitoring of internal combustion engine, earthquake early warning. The researches of the fiber sensors are focused on the novel structure, the enhancement of the sensitivity, measurement of multi-parameters and the decrease of cross-sensitivity. The development of optical fiber sensors is in different areas including new sensor structure, enhancement of sensitivity, simultaneous measurement of multiparameter, and reduction of cross sensitivity. In this paper, we investigate two kinds of optical fiber sensors based on fiber microcavity. Several works are carried out as follow:In chapter1, the types, research status and significance of the optical fiber sensors are shown at first. Then, the optical fiber sensors based on microcavity and their manufacture methods are introduced. At last, the main contents and innovation of this paper are summarized.In chapter2, the interference theory of light, the principles of Fabry-Perot interferometer and Mach-Zehnder modal interferometer are introduced. To support the subsequent experiments, the theory of two-beam interference and modal interference are analyzed.In chapter3, the manufacture method of bubble-expanded Fabry-Perot interferometer (BE-FP) is introduced. The effect of the microcavity size to strain sensitivity is investigated, and the reason of strain sensitivity enhancement is analyzed. Experiment results are consistent with the theoretical analysis and simulations.In chapter4, the Mach-Zehnder modal interferometer (MZMI) based on a microcavity is proposed. The effect of the length of MZMI and the value of core-offset to the transmission spectra is investigated. The temperature and strain responses are experimentally researched, which indicate that the MZMI has a high high-temperature sensitivity (0.166nm/℃) and a similar strain sensitivity with fiber Bragg grating (FBG).