Research On Micro-displacement Sensing Based On Optical Fiber Ring Resonators Of Different Configurations

Owing to its sensitivity to the environmental conditions, optical fiber ring resonator has important application potentials in optical sensing. In this thesis, micro-displacement sensing ability of three configurations of fiber ring resonators are researched. For a single ring resonator, based on its transmission characteristics its response range and sensitivity of micro-displacement sensing is analyzed. For coupled double-ring resonators, the impacts of different structure parameters on the transmission characteristics are calculated and summarized. Analysis indicates that we cannot add displacement one of the rings for sensing, but adding displacement on both rings and using the coupled resonator induced transparency effects to sense has the advantage of having a bright response peak. For a nested ring resonator, we derive the expression of the transmittance and its fundamental transmission characteristics. Based on these the conditions of the critical coupling and coupled resonator induced transparency are provided as the length ratio of the U-shaped loop and the inner circled ring is an integer or half-integer. This lay a foundation for further study of this configuration. The feasible scheme for applying a nested ring on micro-displacement sensing is given. It is shown that when the length ratio of the two rings is an integer, its response range is twice the same-sized single ring resonator. Work in this thesis provides a reference for using optical fiber ring resonators to realize high sensitivity micro-displacement and refractive index sensing. The conclusions in it are also applicable to sensing based on optical waveguide ring resonators.