GATED FIBER OPTIC ROTATION SENSOR WITH EXTENDED DYNAMIC RANGE

摘要

GATED FIBER OPTIC ROTATION SENSOR WITH EXTENDED DYNAMIC RANGE A fiber optic interferometer sensor, employing the Sagnac effect comprising all fiber optic components positioned along a continuous, uninterrupted strand of fiber optic material. The sensor includes a detection system utilizing a modulator or modulators for phase modulating at first and second frequencies light waves which counter-propagate through a loop formed in the fiber optic strand. The second modulation frequency is much lower than the first frequency. An output signal from the sensor is gated synchronously with respect to the phase modulation at the second frequency so that the detected optical output signal is provided only during selected intervals of the phase modulation at the second frequency. A detector generates a feedback error signal proportional to the magnitude of the optical output signal at the first phase modulation frequency. The feedback error signal controls a modulator which controls the amplitude of the second frequency driving signal for the phase modulator such that the signal at the first phase modulation frequency in the output signal from the rotation sensor is substantially cancelled by the phase difference modulation produced at the second modulation frequency during the interval when the optical output signal is present.