DEVELOPMENT OF NOVEL OPTICAL FIBER SENSORS BASED ON THE MODAL INTERFEROMETER STRUCTURE

Abstract

In recent years, an in-line fiber modal interferometer becomes popular due to its simple structure, low cost, high sensitivity, and good fabrication reproducibility, etc. Various modal interferometer structures have been proposed for fiber sensors and filters applications. In this thesis, three types of fiber MI sensors are theoretically and experimentally investigated, including a cascaded fiber interferometer, a dual-core photonic crystal fiber based modal interferometer and a seven-core fiber based modal interferometer. As fiber sensors, they present comparatively high sensitivity, high extinction ratio and good reproducibility, which are suitable for practical sensing applications. In addition, a deep neural network for simultaneous measurement of refractive index and temperature based on the dual-core photonic crystal fiber based modal interferometer is analytically and experimentally demonstrated, which presents the higher measurement accuracy compared with the traditional coefficient matrix inversion method.