Litton Systems, Inc.

Northrop Grumman Systems Corporation

John R Hall

Daniel A Tazartes

Edward Kanegsberg

Thomas McLean

David F Libman

A system and method for providing a rotation sensor for use in a fiber optic gyroscope including a centrally-located cylindrical hub having an improved slip interface positioned there around. The central hub has a substantially planar mounting flange extending from one of its ends, where the axis of rotation of the central hub is orthogonal to the plane of the mounting flange. A sensor coil comprising a plurality of layers of coaxial turns of optical fiber embedded in a potting material is formed around an outer surface of the interface. The interface allows the potted coil to expand or contract along the axial direction of the central hub due to thermal expansion while maintaining a constant thermal and mechanical connection between the interface and the potted coil. In this manner, the present invention maintains the integrity of the potted coil and its connection to the interface during thermal expansion of the potted coil, thus minimizing temperature-induced Shupe bias errors in the rotation sensor.

System and method for providing an improved IFOG hub to coil thermal and mechanical slip interface

A phase and intensity modulated IFOG has a light source responsive to an intensity modulation signal for providing an intensity modulated light signal. A Sagnac interferometer has a fiber optic coil. The coil receives and circulates a clockwise and counter-clockwise beams. The Sagnac interferometer is responsive to an intensity modulated light signal at a first input port, and to a phase modulation signal at a phase modulation input terminal for outputting a non-reciprocal interference signal. A PSD detector system responds to the non-reciprocal interference signal and provides a demodulated bias signal. An intensity signal generator has an output that provides the intensity modulation signal. A phase signal generator provides the phase modulation signal to the phase modulation input terminal. The intensity signal generator and the phase signal generator have a common frequency. The phase difference &thgr; between the phase modulation signal and the intensity modulation signal is adjustable in response to at least a first control signal. A computer with a digitizing sampler is coupled to receive and digitize successive sample values of the demodulated bias signal. The computer executes a program that adjusts the phase difference &thgr; between the intensity modulation signal and the phase modulation signal to drive the amplitude of the sample values of the demodulated bias signals to a minimum. The computer program successively calculates and outputs an estimate of the input rotation rate about the Sagnac sensitive axis as a function of the phase angle &thgr;.

Phase and intensity modulated IFOG

A method for measuring intensity-type polarization non-reciprocity (PNR) bias error in an interferometric fiber optic gyroscope (IFOG) using birefringence modulation. The counter-propagating waves in the fiber optic loop of the IFOG are modulated with a slowly varying voltage signal, such as a triangle wave, ramp or sine wave signal, to cause birefringence modulation. A peak-to-peak amplitude of a resultant output signal is measured to determine the intensity-type PNR bias error of the IFOG.

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Woodland Hills, CA, United States of America

John R Hall