Patent ID: 7295322

Claim:
In a closed loop interferometric fiber optic gyroscope (IFOG) having a light source, an optical circuit splitting the light into counter-propagating first and second light signals, a means for combining the light signals so that the second light signal is out of phase with the first light signal by a first phase difference, and a controller demodulating the combined signals and adapted to derive an interference signal therefrom, a system for measuring optical power of the IFOG comprising: a phase modulator generating a phase modulation signal to the optical circuit to establish the first phase difference; a timing pulse generator coupled to the phase modulator and triggering a temporary change in the phase modulation signal causing a second phase difference between the first light signal and the second light signal during one or more cycles of modulation; a comparator comparing a first interference signal derived by the controller during a modulation cycle in which the first phase difference occurs to a second interference signal derived by the controller during a modulation cycle in which the second phase difference occurs, to obtain a result representing the optical power; and a delay unit ensuring simultaneous presence of the first and second interference signals at the comparator.