Performance analysis of an all-fiber resonant-ring interferometric sensor

An all-fiber resonant-ring interferometer is proposed for use as a sensor. A performance analysis has been made to show how the output characteristics depend on the coupling condition in an evanescent-field directional coupler that forms a fiber ring and on some fiber parameters as well as on the temporal coherence of a light source. These parameters play a critical role in characterizing the output performance. If a light source with a coherence factor larger than 0.95 is provided, the resonant-ring interferometer would be available as a practical sensor. The minimum detectable phase change in the fiber ring is predicted to be <5 × 10−8 rad, as a typical example.