Fiber Optic Sensors Based on the Sagnac Interferometer and Passive Ring Resonator

This chapter begins with an introduction to the use of the Sagnac interferometer and passive ring resonator for rotation sensing. This includes an introduction to the Sagnac effect and continues with a discussion of its first commercial implementation in the form of the ring laser gyro. This is followed by a description of fiber optic gyros in both the Sagnac interferometer and passive ring resonator configurations for open and closed-loop operation. The main thrust of fiber optic gyro development has been to isolate all environmental effects other than rotation from these sensors. Three basic methods are used to form optical rotation sensors: (1) optical resonators, (2) open-loop interferometers, and (3) closed-loop interferometers. The Sagnac interferometer has been of considerable importance to the field of inertial navigation, and the fiber optic gyro promises to be the first high-value commercial fiber optic sensor product. Controlled Vocabulary Terms fibre optic gyroscopes; optical resonators; ring lasers; sagnac interferometers