FIBER-OPTIC GYROSCOPE WITH A DUAL-INJECTION POLARIZATION- MAINTAINING 3X3 DIRECTIONAL COUPLER FOR ENHANCED MEASUREMENT SENSITIVITY THROUGH HETERODYNE

An improved fiber-optic gyroscope (FOG) is proposed for enhancing the optical measurement sensitivity through the application of a heterodyne effect. The improved FOG is characterized by the use of a dual-injection polarization-maintaining 3×3 directional coupler which is configured to receive a pair of source light beams that are injected thereinto in a bi-directional manner. The forward-injected light beam is used to be split into a pair of interrogating beams for use by a coiled optical fiber to implement the detection and measurement of the Sagnac effect due to a rotational movement. On the other hand, the backward-injected light beam is used to be mixed with the paired interrogating beams that have passed through and returned from the coiled optical fiber to thereby provide a heterodyne effect that can boost the differential optical power amplitude of the paired interrogating beams, thereby enhancing the optical measurement sensitivity of the FOG application.