Apparatus and method for phase modulating optical signals in a fiber optic rotation sensor

Abstract From the Canadian patent

The operating point of a fiber optic rotation sensor is shifted to obtain an increased sensitivity in the measurement of the Sagnac phase shift between counterpropagating beams in a sensing loop. The two counterpropagating optical waves are mixed for detecting interference of the waves to indicate the phase difference between them. The phase of the waves is modulated in accordance with a periodic function having a frequency equal to fs = where t is the transit, time for an optical wave in the sensing loop. The interference pattern of the two waves is periodically sampled at a frequency equal to the modulation frequency.