Abstract

Reentrant fiber optic gyroscopes offer the advantages of an inherent linear scale factor and a frequency readout, as in ring laser gyroscopes, but without associated lock-in effect. In the re-entrant gyroscope scheme, counterpropagating signal pulses can recirculate many times around a closed fiber loop, which enhances the Sagnac effect proportionally to the number of recirculations. When optical gain is provided in the loop to compensate for the round-trip signal loss, a large number of recirculations can be obtained, permitting sensitive rotation measurement. The system output then consists of a pulse train with sinusoidally modulated envelope. The modulation frequency is given by F = Dü/ηλ, where D is the loop diameter, n the refractive index at the signal wavelength A, and Ω the rotation rate.

© 1986 Optical Society of America