Fiber optic gyroscopes for vehicular use

The measurement of rotational motion is an essential element of vehicle navigation and stabilization. Interferometric fiber optic gyroscopes (IFOG) are becoming affordable for many such applications. They offer the advantages of high reliability, resistance to shock and vibration, and repeatability over time and temperature. Based on the Sagnac effect, the IFOG has no moving parts, and consists of a fiber sensing coil, semiconductor light source, photodetector, polarizer, one or more directional couplers, and signal processing electronics. Only the “open-loop” signal processing approach is economic for land navigation use, with its simplified electronics and all-fiber optical circuit construction. It is now possible to produce an optical circuit using only one directional coupler, further simplifying the construction and reducing cost. Both types of open-loop gyro are in production. Performance data for bias and scale factor versus temperature as well as rate linearity, are presented