Patent ID: 8294900

Claim:
A resonant fiber optic gyroscope (RFOG) having a residual intensity modulation (RIM) controller, the controller comprising: an intensity modulator optically coupled to receive a light beam from a laser source modulated at a resonance detection modulation frequency; an optical tap device optically coupled to the intensity modulator; and a demodulating feedback servo coupled to the optical tap device and the intensity modulator, the demodulating feedback servo generating a sinusoidal feedback signal to the intensity modulator; wherein the demodulating feedback servo adjusts an amplitude and phase of the sinusoidal feedback signal provided to intensity modulator based on a residual intensity modulation detected by the demodulating feedback servo wherein the demodulating feedback servo comprises: an in-phase demodulator that demodulates using a first reference frequency at the resonance detection modulation frequency to produce a first error signal that represents an in-phase component of the intensity modulation; a quadrature-phase demodulator that demodulates using a second reference frequency at the resonance detection modulation frequency to produce a second error signal that represents a quadrature-phase component of the intensity modulation; wherein the demodulating feedback servo adjusts the amplitude and phase of the sinusoidal feedback signal based on driving both the first error signal and the second error signal to zero.