Fiberoptic gyroscope with passive phase detection for low cost application

In this paper a passive fiber optic gyroscope without non-reciprocal phase modulation is presented. A fused fiber 3×3 directional coupler provides a constant phase shift thus enabling the detection of rotation rate at the quadrature point. Bias and scale factor errors due to indeterministically changing birefringent coupling centers in the non-polarization preserving monomode fiber coil are eliminated by using a contrast insensitive signal recovery scheme. A simple temperature compensation procedure has been implemented in the gyro software which yields a bias stability of less than 0.04°/s and scale factor errors of less than 0.5% in the whole temperature range from -40 °C to +70 °C.