Litton Systems, Inc.

Karlheinz vonBieren

Donald A Frederick

Akbar Arab-Sadeghabadi

A fiber optic sensor system includes a plurality of interferometric sensors arranged in an array to monitor a selected parameter and means for providing two-mode optical signals to each of the interferometric sensors. The two modes have different propagation velocities so that each sensor produces an optical signal indicative of changes in the parameter. A return optical fiber receives signals output from each of the plurality of interferometric sensors. The optical signals in the return fiber are separated and input to a Fourier transform lens that forms a plurality of spatially separated fringe patterns on a grating. Each fringe pattern corresponds to the optical signal output from a selected sensor. A photodetector array monitors the fringe patterns simultaneously and continuously to detect changes in the parameter. A phase modulator modulates the phase of one of the optical sensor signals output from the sensor array. Changes in the parameter either shift the locations of the fringe patterns or produce and additional phase modulation in the fringe patterns.

Coherence multiplexed interferometric signal processing system and method

A photodetector includes a polarizer array and an array of photodetector elements. The polarizer array includes a plurality of polarizers having axes of polarization spaced apart by selected angles such that each optical signal incident on the polarizer array has a polarization component along at least one of the axes of polarization. The array of photodetector elements is arranged such that each of the photodetector elements receives light from a selected one of the polarizers. At least one of the photodetector elements receives parallel polarization components from the optical signals to form an electrical signal indicative of interference between the optical signals.

Optical signal detection apparatus and method for preventing

A hydrophone is formed of first and second optical fibers coupled together to form a fiber optic interferometric sensor for sensing an acoustic signal. The optical fibers are wrapped around a pair of concentric, thin-walled hollow cylinders. The fiber wrapped around the inner cylinder is the reference leg of the interferometer and the fiber wrapped around the outer cylinder is the signal leg. The reference leg is exposed to the hydrostatic pressure but isolated from the acoustic signal. The sensing leg is exposed to both the hydrostatic pressure and the acoustic wave signal. The signal output from the interferometer is indicative of changes in the acoustic wave signal.

Polarization insensitive hydrophone

A ring laser gyro frame of ceramic material having therein lithium ions for dimensional stability over a change in temperature. Either a slot is formed in the ceramic material, a secondary negative electrode is placed spaced apart from the ceramic material to warp the electric field, or both.

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Camarillo, CA, United States of America

Karlheinz vonBieren