Optical gyroscope system

Abstract

An optical gyroscope is described of the type which passes light beams in opposite directions through a single mode fiber optic wave guide that extends in a circle or coil, and which enables measurement of rotation rate of the coil by measuring the relative phase shifts of the beams by interferometric techniques, wherein simplification and enhanced accuracy are obtained. Beam splitting and phase shifting of the light is facilitated by utilizing brief pulses of light and by using light-controlling devices which are operated for a brief time only when the light pulse passes in one direction through the device but not at a different time when the pulse is passing in the opposite direction through the device. High accuracy in rotation measurement is achieved at both very slow and very fast rotation rates, by alternately operating the system so that at zero rotation the interfering waves are alternately 90.degree. out of phase and in phase. Linear polarization of the light beams is maintained by coiling the full length of the optic fiber in a single plane so that bending stresses induce a birefringence in the waveguide, thus altering the propagation constants of the two polarized modes and decoupling them.