Method of detecting a signal and modulation coefficient of a phase- modulated fiber-optic gyroscope based on a difference in the duration of multiple subwaves in a modulation period

摘要

An AC component of the photodetector includes two quasi-sine waves in a cycle of phase-modulation. T.sub.1 and T.sub.2 are time lengths of the quasi-sine waves. When a fiber coil is rotating, T.sub.1 differs from T. sub.2. The difference between T.sub.1 and T.sub.2 is in proportion to an angular velocity of the fiber coil. This invention obtains the angular velocity by measuring time durations T.sub.1, T.sub.2 or both T.sub.1 and T.sub.2. Zero-crossing detection defines the moments of the beginning and the end of T.sub.1 and T.sub.2. Since this gyroscope depends on the measurement of time lengths, it is fully immune from the fluctuation of light power due to the light source, or the fluctuation of the gain in the electric circuit.