Research On Optical Fiber Sensor Based On Peanut Shape Structure

Optical fiber Mach-Zehnder interferometer is a kind of typical optical fiber sensor. The fiber core and cladding are the reference and interference arm of the interferometer respectively. Fiber Mach-Zehnder interferometer is widely used in the field of optical fiber sensors because of simple structure and large sensitivity. In this paper, a new Fiber Mach-Zehnder interferometer based on peanut shape structure is proposed and used for the measure in the experiment.The main work of this thesis as follows:1. The principle of the interferometer is discussed and the field distribution of core and cladding is simulated. The fabrication of peanut shaped structure is introduced and the frequency spectrum of interference spectrum is also analyzed. In the liquid level experiment, the sensor is used for the measure of the height of the liquid. The sensitivity is discussed when refractive index of the liquid is changed. The relationship of the length of the sensor and the sensitivity is also elucidated.2. A fiber Mach–Zehnder interferometer based on lateral-offset and peanut shape structure is proposed and demonstrated for the measure of curvature and liquid level. The lateral-offset structure is spliced to excite cladding modes and adjust the intensity of core mode and cladding mode. The principles of the curvature and the liquid level measurement are introduced.3. An optical fiber sensor based on the FBG and peanut shaped structure is proposed. The sensor consists of a fiber MZI and FBG. A simultaneous measurement of temperature and curvature is realized. In the temperature experiment the pure sensitivity to the temperature of MZI and FBG are obtained. In the curvature experiment the sensitivity to the temperature of FBG is obtained. We can obtain the relationship between the wavelength shifts and the changes of curvature and temperature in a matrix. The cross sensitivity of temperature is eliminated and the scope of application of sensor is expanded. The reflectance spectra of the sensor is also used for curvature experiment.