Open Loop Fiber Optic Gyroscope : A Technical Note

Abstract

This technical note describes the design and fabrication of a prototype open-loop interferometric fiber-optic gyroscope (IFOG). The gyro transfer function is transposed from that of a raised-cosine to a sine function using AC modulation, giving maximum sensitivity at rest. Among various signal processing methods, lock-in principle is used to detect the Sagnac phase shift due to rotation. Initial work is done with bulk-optic components. Finally, all-fiber gyroscope is built using laser diode (1300 nm), PINFET detector, fiber couplers and PZT phase modulator. An effort is made to develop compact IFOG with sensing coil diameter of 10 cm and signal processing card of size 10 x 6.5 sq cm. The present set-up is able to detect the direction of rotation at a rotation rate of 5 x 10/sup -4/ radian per second. Presently, the performance of the set-up is limited by the difficulty in achieving complete reciprocity.