Closed-loop fiber-optic angular rate sensor including a mixer arrangement for measuring rotational direction and rate

摘要

The direction and rate of rotation of a closed-loop fiber- optic angular rate sensor is determined by employing acousto-optic modulators in each arm of the sensor and determining the frequency difference between the modulators. Since the modulators operate at a relatively high frequency, frequency measurements to within several hertz are implemented by providing the difference frequency and the sign of the difference frequency via the use of electronic mixers. Since the maximum difference frequency is in the order of a few megahertz, standard counters can thus be used to accurately measure the reduced frequency and hence provide information relating to the direction and rate of rotation.