Abstract: A fiber optic Sagnac interferometer for measuring rotation rate includes a light source that is ON/OFF keyed in a predetermined cycle. After filtering of the readout signal in the course of demodulation, a substantially-lower readout signal carrier frequency, and, thus, corresponding-lower demodulator requirements, may be achieved. A closed loop configuration is disclosed, associated with a scale factor controlling circuit, for rotation rate sensors with keyed light sources. The invention is particularly suitable for fiber optical rotation rate sensors with short sensor coils.

Abstract: In a fiber optic interferometer rotation rate sensor reset by phase ramp via a digital control circuit to undertake the reversal required to obtain the scale factor error information, a reciprocal, alternating phase shift that is not a function of the angle of rotation, but has a fixed timing, is synchronized with gyroscope modulation frequency to avoid lock-in, and scale factor nonlinearities, particularly in the case of low rates of rotation. Even in the case of low rates of rotation, a scale factor error correction is possible and lock-in, caused by variations in bias in the case of the modulation deviation reversal, is avoided.