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.

Abstract: Adaptive speech recognition is improved by extracting an estimate of the background noise during unknown speech input, and using the noise estimate to modify the noiseless prestored reference speech signals for comparison with the input. Averaged values of autocorrelation coefficient and Toeplitz matrix elements representative of noise frames and prestored reference frames are used to calculate the LPC predictor signals.

Abstract: An optical rate sensor (200) is disclosed for use in inertial reference systems to measure rates of angular rotation with substantially high resolution and sensitivity. The sensor (200) comprises a passive ring Sagnac interferometer (201) with a multiturn fiber optic ring (232) through which counter-propagating optical waves are transmitted. A nonreciprocal time variant phase modulation is applied to the waves along with periodic effective transposition of ring ports. The waves are combined to produce a "zero order" fringe pattern having an intensity varying in accordance with the relative phase between the counter-propagating waves. An intensity signal is derived from the fringe pattern having a phase offset corresponding to the Sagnac induced phase shift which in turn is linearly proportional to the angular rotation rate of the passive ring. Sampling, averaging and estimation circuits detemine the offset by detecting zero-crossing locations of the signal.