Detection of phase disturbance in the fiber optic Sagnac interferometer

Unified physical interpretation of spatial and frequency characteristic of fiber optic loop interferometer is presented. The existence of insensitiveness regions of this interferometer and its periodic frequency characteristic is shown. It is also demonstrate that such an interferometer may be used as a distributed sensor for localization of a disturbance, because its response is linearly dependent on the position of this disturbance in relation to the loop.