Abstract: A system for tuning out an error signal in high performance fiber optic gyroscopes includes a compensation network having both active and passive filters which include the necessary pole and zero to cancel out the error signal. The entire system includes a fiber optic gyroscope connected to an amplifier, signal processor, square wave detector, modulator driver and the compensation network. The compensation network is connected between the modulator driver and the phase modulator of the fiber optic gyroscope.

Abstract: A closed loop fiber optic gyro features signal processing wherein square wave phase modulation is added to a modulation drive signal after overflow logic so that the square wave modulation will not cause a phase modulation ramp to exceed overflow/underflow logic limits. The arrangement is such that the phase modulation causes a retrace with each modulation period when the amplitude of the ramp is within predetermined limits. A variable time constant in a retrace correction loop gives better retrace limit correction performance when the gyro is first turned on as during a "warm-up" period. The amplitude of the gyro square wave output is determined by taking the difference between the output of the first half cycle of the square wave modulation and the average of adjacent second half cycles thereof. An error signal for a retrace limit is developed by considering changes in the square wave amplitude and not the square wave amplitude itself.

Abstract: A closed loop fiber optic gyro features signal processing wherein square wave phase modulation is added to a modulation drive signal after overflow logic so that the square wave modulation will not cause a phase modulation ramp to exceed overflow/underflow logic limits. The arrangement is such that the phase modulation causes a retrace with each modulation period when the amplitude of the ramp is within predetermined limits. Corrections to the retrace limit are implemented so as to scale a digital output, which enables the determination of accumulated gyro angle with a finer resolution than simple output pulse accumulation as has heretofore been the case.

Abstract: A closed loop fiber optic gyro features signal processing wherein square wave phase modulation is added to a modulation drive signal after overflow logic so that the square wave modulation will not cause a phase modulation ramp to exceed overflow/underflow logic limits. The arrangement is such that the phase modulation causes a retrace with each modulation period when the amplitude of the ramp is within predetermined limits. The square wave amplitude from a cycle immediately after a retrace is considered as errant data that should be excluded from a phase nulling loop. Thus, the phase nulling loop has more accurate input data so that feedback will be accomplished more effectively for improved gyro performance.

Abstract: 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.