Abstract: A control arrangement for minimizing optical leakage in a time-division, multi-stage electro-optical switch by the periodic adjustment of switching voltage levels. An optical detector connected to an idle port of the switch transmits a leakage signal which represents optical leakage in the switch in various configurations of the switch. The leakage signal is filtered by a low pass filter and sampled at a low rate. A processor stores the sampled data and periodically analyzes the data to determine the appropriate changes in the switching voltage levels for each of the stages of the switch to minimize optical leakage. An output circuit connected to the processor and the switch modifies a previously determined base voltage signals for each of the stages to incorporate the voltage level changes and applies the modified signals to the switch in the appropriate time slots.

Abstract: A rectification error reducer for a fiber optic gyroscope, which is an intensity servo or compensator for reducing vibration effects in the optical signals caused by modulation at vibration frequencies induced by the gyroscope operating environment. The vibration effects may be detected in signals from the photodiode output in amplitude form which is used in a control system to null out optical intensity variations at the frequencies of vibration.

Abstract: A rectification error reducer for a fiber optic gyroscope, which is an intensity servo or compensator for reducing vibration effects in the optical signals caused by modulation at vibration frequencies induced by the gyroscope operating environment. The vibration effects may be detected in signals from the photodiode output in amplitude form which is used in a control system to null out optical intensity variations at the frequencies of vibration.

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: A triad sensor apparatus (300) comprises a passive ring Sagnac interferometric arrangement having a light source circuit (308) and a series of three multi-turn fiber optic rings (302, 304, 306). An optics/modulator circuit (312) is adapted to selectively switch optical waves emitted from the light source circuit (308) and transmit the signals through the corresponding fiber optic rings as counterpropagating optical waves. Nonreciprocal phase modulation is applied to the counter-propagating waves, and the waves are recombined so as to produce a "zero order" fringe pattern having an intensity varying in accordance with the relative phase between the counterpropagating waves. Optical waves from the light source circuit (308) are selectively applied to a ring path during a given time period, while the photodetector circuit (324) is detecting light waves which have emerged from another ring path during the same given time period.

Abstract: A heading reference system (100) for sensing vehicle heading relative to fixed inertial space is mountable in a vehicle such as a land-based vehicle and includes a two-degree-of-freedom (TDF) dynamically tuned gyroscope (150) responsive to vehicle rotation about pitch and yaw axes for generating rate signals indicative of the rotation. A caging loop (160) generates force signals for torquing the gyroscope (150) to a null position. A pair of accelerometers (186, 187) are responsive to misalignment of the vehicle relative to a horizontal plane formed by the pitch and roll axes. Processor circuitry (180) is responsive to the force signals, the misalignment of the vehicle relative to pitch and roll axes, and distance signals generated by an odometer unit (140) to apply heading signals to an indicator unit (120) for visually indicating to a vehicle operator the directional heading.