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Abstract

An optical rate sensor (300) is disclosed for use in inertial reference systems to measure rates of angular rotation with substantially high resolution and sensitivity. The sensor (300) comprises a passive ring Sagnac interferometer (302) with a multiturn fiber optic ring (308) through which counter-propogating optical waves are transmitted. A non-reciprocal phase modulation is applied to the waves, and the waves are combined to produce a 'zero order' fringe pattern having an intensity varying in accordance with the relative phase between the counter-propogating waves. The phase modulation is under control of modulated control signals which are functionally related to measured values of the angular rotation rate. The phase modulation thereby produces an intensity signal which tends to alternate between values of substantially maximum change with respect to given changes in phase shift resulting from the non-reciprocal phase modulation. The optical rate sensor (300) also includes an analog integrator (364) and a central processing unit (384) which provides for optimal control and filtering for determination of the rate of angular rotation and appropriate control signals to be applied to the non-reciprocal phase modulator. The central processing unit (384) also includes an arrangement whereby a relatively wide dynamic range is achieved with substantially minimal errors in rate determination and with the use of a physically realizable digital-to-analog converter through an arrangement whereby the most significant bits of the determined control signals are 'stripped off' prior to application through a digital-to-analog converter (392).

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First Claim