Litton Systems, Inc.

Northrop Grumman Systems Corporation

Ralph A Patterson

John P Rahn

Ronald James Michal

George A Pavlath

Amado Cordova

Sidney X Huang

Eric Lee Goldner

Henry C Abbink

Christine E Geosling

Edward Kanegsberg

Thomas McLean

Robert J Hoover

James R Steele

Robert A Mitchell

John D Wilde

Bernard C Fidric

An apparatus and method is provided for facilitating ionization of a gas medium of a laser gyroscope. The apparatus and method employ a solid state light emitting device as a start aid for the laser gyroscope. The solid state light emitting device has a wavelength at or below a threshold wavelength based on a work function of a cathode coating material to prompt ionization of a gas medium within the laser gyroscope.

Apparatus and method to facilitate laser gyroscope ionization

An NMR gyroscope in one example comprises a support structure affixed within an enclosure, an NMR cell affixed to the support structure, a plurality of permanent magnets disposed about the NMR cell to produce a magnetic field within the cell, and a field coil disposed proximate the cell to produce a modulated magnetic field transverse to the magnetic field produced by the permanent magnets.

NMR gyroscope

A method and apparatus for reducing the temperature-dependent Shupe bias of a potted gyro sensor coil pack to near-zero is provided by selectively adjusting the manner in which CCW and CW fiber leads are attached to the coil pack or the coil mount. The invention recognizes the inevitable existence of a strain differential between the CW and CCW-wound portions of a symmetrically-wound fiber coil. Leads affixed to the ends of the CW and CCW-wound halves of the coil are selectively bonded in accordance with principles for creating a counteracting temperature-dependent stress differential whereby temperature-dependent Shupe bias is substantially eliminated from the gyro output.

Method for stress tuning fiber optic sensor coils

The invention is a method and apparatus for quantitatively characterizing the pressure-induced nonreciprocity of a fiber-optic coil where the pressure-induced nonreciprocity is a property of a fiber-optic coil which pertains to the degree to which light beams, initially in phase, differ in phase as a result of traversing the fiber-optic coil in reverse directions while the fiber-optic coil is being subjected to a time-varying pressure. The method comprises the steps of applying time-varying pressure to the fiber-optic coil for a predetermined time period, measuring the phase difference of light beams traversing the fiber-optic coil in reverse directions during the predetermined time period, and obtaining a measure of the nonreciprocity of the fiber-optic coil utilizing the measured phase difference. If the time-varying pressure is specified by a first function of time, the measure of the nonreciprocity is the integral over the predetermined time period of the product of a second function of time and either (1) the phase difference of light beams traversing the fiber-optic coil in reverse directions during the predetermined time period or (2) the integral over time of the phase difference. The second function is chosen such that the measure of the nonrecipocity has a signal-to-noise ratio of at least one. Preferably, the second function is (1) an approximation of the time derivative of the first function if the product involves the phase difference or (2) an approximation of the first function if the product involves the integral of the phase difference. The invention also includes the apparatus for practicing the method.

Method and apparatus for determining the pressure-induced nonreciprocity

A rotation sensor for use in a fiber optic gyroscope includes a substantially-planar disk-like coil mounting member of titanium. A would sensor coil is supported by the member in an edgewise fashion, allowing free expansion of the sensor coil in the direction orthogonal to the plane of the member to minimize thermally-induced stressing of the sensor coil. In an alternative embodiment, the free-standing coil is effectively 'split'; that is, one-half is mounted to one side of the member and the remainder to the other side in such a way that the sensitive axes are coincident. Edge ramps are provided in the member for guiding the continuous optical fiber comprising the coil segments from one side of the disk-like mounting member to the other without microbends. A cylindrical inner hub includes thinned and flexible portion for contacting a mounting pedestal of stainless steel composition whereby the differential thermal expansions of the pedestal and mounting member materials will not produce misalignment of the sensor coil with respect to a predetermined input axis of rotation.

Flange-supported sensor coil for a fiber optic gyroscope

A power boosted source of broadband optical power comprising a broadband light source, optical fiber amplifier and a relative intensity noise reduction system. The optical fiber amplifier amplifies the power level of the optical input signal to provide a power boosted source of broadband optical power out of an output port. A coupler samples a portion of the broadband optical power out of the output port as a sample portion signal. A detector and transimpedance amplifier detect the optical signal and provide a buffered signal having an instantaneous amplitude that faithfully characterizes the intensity of the sample portion signal. A bandpass amplifier amplifies the buffered signal and provides an output control signal to a light source responsive to a composite bias and control current for providing an output optical signal. The output optical signal is coupled to the input of the optical fiber amplifier to be the optical input signal to the optical fiber amplifier. The output optical signal from the ELED has a substantially constant output intensity level and smooth and bell shaped broad band spectrum with a center optical wavelength within the gain bandwidth of the optical fiber amplifier.

Optical fiber amplifier eled light source with a relative intensity

A potted sensor coil for a fiber optic gyroscope includes an inter-layer stress relief layer of lubricating material. The coil is wound into a known pattern. Various coil configurations can be realized in which a coating layer of lubricant relieves stressing at the interface between the outer jacket of the fiber and the coil potting material.

Potted gyro sensor coil with inter-turn stress relief

A fiber optic sensing coil formed in a polarization-maintaining optical fiber has two optical fiber leads extending therefrom. A multifunction integrated optics chip linearly polarizes optical signals input to the sensing coil. Fiber optic leads formed of polarization-maintaining optical fiber extend from the multifunction integrated optics chip. The fiber optic multifunction integrated optics chip leads are arranged such that the linear polarization of optical signals output from the multifunction integrated optics chip is directed along one of the principal axes of birefringence of each of the fiber optic multifunction integrated optics chip leads. Splices are formed between corresponding the first sensing coil leads and the multifunction integrated optics chip leads. The sensing coil leads and the multifunction integrated optics chip leads are arranged such that their corresponding principal axes of birefringence are at angles of approximately 45.degree. relative to one another. The first splice is formed a distance from the multifunction integrated optics chip such that a selected phase change between polarization components occurs in optical waves that propagate the distance L.sub.1 in the first multifunction integrated optics chip lead.

Depolarized fiber optic rotation sensor with low faraday effect drift

Apparatus for suppressing the bias errors induced by the Faraday effect in the output of a sensor coil exposed to a magnetic field. Arrangements are formed at two leads of the sensor coil for compensating the bias shifts. One of such arrangements comprises at least one loop of optical fiber for compensating the effect induced by the magnetic field component oriented transverse to the axis of the sensor coil while the other comprises at least one loop oriented at a predetermined pitch angle for compensating the effect induced by a magnetic field component along the axis. In each case, a predetermined degree of twist of a preselected fiber twist mode is imposed upon the compensator loop for creating a counteracting, corrective Faraday effect. Cross-coupling does not occur between the two compensators as their twist rate perodicities are unequal.

Apparatus for reducing magnetic field-induced bias errors in a fiber

A method for tuning a sensor coil for a fiber optic gyroscope. The coil is initially wound in a known pattern. One end of the fiber of the wound coil is then adjusted relative to the other end so that a known differential is obtained that effectively displaces the midpoint of the winding pattern. The coil is then attached to an interferometer test apparatus and performance measured. After successive observations a 'trimmed' coil is obtained of acceptable performance characteristics.

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Moorpark, CA, United States of America

Ralph A Patterson