Phase-locked loop laser gyroscope system

Abstract

A very high resolution laser gyroscope system having a phase-locked loop operatively coupled to the output of a laser gyroscope cavity. A difference frequency signal is formed between two output beams from the gyroscope cavity. The phase of the difference signal is compared with that of a reference clock to produce a signal representative of the phase difference between the reference clock and difference signal. The latter signal is amplified and coupled to a coil which produces a field within a Faraday rotator body disposed in the wave propagation path within the laser gyroscope cavity. The phase of the difference signal is thus phase-locked to that of the reference clock signal so that the frequency difference between the two beams in the cavity is maintained constant over a wide range of rates of rotation.