Litton Systems, Inc.

Copley Networks, Inc.

Ronald James Michal

David Michael Rozelle

Ralph A Patterson

George A Pavlath

Amado Cordova

Leo K Lam

James R Steele

Sidney X Huang

Gregory Scott Moore

Fernando Torres

Eric Lee Goldner

John P Rahn

Mark E Jones

John F Cappi

Chin L Chang

Bernard C Fidric

Trong-Huang Lee

Jyl Ren Dent

An optical fiber interleaver and method for aligning the output channels to a set of nominal values in frequency space. The interleaver is formed of two optical fibers joined together at fused input and output couplers to define an input section, an interferometer section and an output section. Within the interferometer section, an element is arranged to vary the optical path length of at least one of the fibers in response to a feedback signal. The feedback signal is generated by examination of the intensity of a monitor signal at the output section that was applied at the input section.

Tuned fiber optic interleaver

An optical interleaver. The interleaver is based upon the Mach Zender interferometer. At least one of the optical paths joining opposed couplers of the arrangement includes an optical image transfer element intermediate the ends of fibers associated with the couplers. In one embodiment, the optical image transfer element is a single imaging lens whereas, in another embodiment, the element consists of an aligned pair of collimating lenses. During fabrication, optical positioning stages support the optical image transfer element and fiber ends to permit ready adjustment of &Dgr;&THgr;, the optical path length difference between the arms of the interleaver, to assure predetermined optical channel spacing of an input DWDM signal.

Optical interleaver with image transfer element

A source, system and method for generating amplified stimulated emission is provided. The source includes a pump source for generating a pump light which is provided to a doped element, such as a doped fiber. Based on the pump light, the doped fiber, which may be a erbium doped fiber, generates the amplified stimulated emission. A coupler mechanism provides the pump light to the doped fiber and transmits the amplified stimulated emission from the doped fiber. The coupler mechanism isolates the pump light and the amplified stimulated emission using phase conditions. A system is also provided including a source and a sensor, such as a fiber optic gyroscope. A method for generating the amplified stimulated emission is further provided.

Source, system and method for generating amplified stimulated emission using a coupler mechanism

A pump light source provides pump light to an optical fiber arranged to guide the pump light to a first optical isolation device. Light output by the first optical isolation device is input to a wavelength division multiplexer. A gain fiber is connected to the wavelength division multiplexer and arranged to be optically pumped by the pump light such that the gain fiber emits broadband light that propagates to the wavelength division multiplexer. An output optical fiber is connected to the wavelength division multiplexer and arranged to guide a portion of the broadband light emitted by the gain fiber to a second optical isolation device for input to a fiber optic rotation sensor.

Double-pass fully isolated broadband optical signal source for fiber optic interferometric sensors

A wavelength stabilized light source is constructed using a lasing element such as a laser diode which generates light that is substantially polarized. This light is conducted through a polarization maintaining optic fiber to a Bragg grating which reflects a portion of the light back to the laser diode forming a virtual laser cavity and stabilizing the wavelength of the laser diode light output over time and a broad range of temperature and drive circuit conditions. To produce a broad band light source, the laser diode light is used to pump an erbium doped fiber. The wavelength stabilized light source can be used in fiber optic gyroscopes as well as in other applications that require a light source with a very stable wavelength.

Wavelength stabilized laser light source

Apparatus for minimizing the effects of radiation induced attenuation on a sense coil in a fiber optic rotation sensor includes apparatus for injecting photobleach light at a frequency selected to remove radiation-induced color centers. Wavelength division multiplexing optical couplers are used to introduce the photobleach light into the fiber optic rotation sensor system and then remove the photobleach light from the gyroscope optical circuit without effecting the gyro signal.

Apparatus and method for isolated photobleaching fiber optic rotation sensor coils

A system and method for providing scale factor stabilization of a broadband light source used in fiber optic gyroscopes is provided. A primary bandpass filter is positioned in the propagation path of the light emitted by the broadband light source to narrow the spectral width of the optical signal transmitted to the fiber optic gyroscope, which reduces the centroid wavelength shift resulting when the broadband light source is exposed to ionizing radiation and other harsh environmental conditions. The filtered optical signal is then passed through the fiber optic gyroscope, where the filter optical signal is processed to measure the amount of rotation of the fiber optic gyroscope. The scale factor stabilization system further includes the spectral monitor array arranged to perform direct optical wavelength measurements of the filtered optical signal to determine whether a scale factor shift in the optical signal has occurred. When a scale factor shift is detected, the detected scale factor shift is used in a compensation algorithm to correct the scale factor of the optical signal. By monitoring the scale factor shift and adjusting the values measured by the fiber optic gyroscope in accordance with the detected scale factor shift, the accuracy of the fiber optic gyro can be improved to a fraction of a part-per-million.

System and method of stabilizing the scale factor shift in fiber optic

A system for performing scale factor stabilization of a broadband optical signal source used in fiber optic gyroscopes in radiation environments. An optical signal source is provided comprising a pump light source and an optical fiber arranged to receive pump light from the pump light source. Light output from the optical fiber is input into a wavelength division multiplexer. An optical gain fiber having an erbium-doped core is connected to the wavelength division multiplexer and arranged to be optically pumped by the pump light such that the gain fiber emits broadband light that propagates to the wavelength division multiplexer. An output optical fiber is connected to the wavelength division multiplexer and arranged to guide a portion of the broadband light emitted by the gain fiber to a fiber optic gyroscope. A filter device is positioned in-line with the broadband light emitted by the gain fiber to attenuate light outside of the bandwidth of the filter device. The filter device allows a bandwidth of light narrower than the spectral width of the broadband light source to propagate through while attenuating all wavelengths of light outside of its operating bandwidth. Only the portion of the broadband source spectrum contained within the bandpass of the filter is selected out, thus narrowing the spectral width of the broadband fiber source. This narrower spectral width reduces the shift of centroid wavelength of the broadband fiber source which results when the gain fiber and other sensitive optical components are exposed to ionizing radiation.

Scale factor stabilization of a broadband fiber source used in fiber

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 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

The ends of a pair of polarization-maintaining optical fibers that each have an elliptical stress member in the cladding to produce stress induced birefringence are placed end-to-end with a predetermined gap between the ends of the fibers. The ends of the fibers are examined with an optical imaging apparatus whose focus is adjusted to locate an alignment band in each fiber. The position of one of the polarization-maintaining optical fibers is then adjusted until the two alignment bands are in longitudinal alignment. The fiber ends are pre annealed and then fused together by application of energy from an electric arc.

Method for splicing polarization maintaining fiber with elliptical

Apparatus and methods for detecting when the birefringent axes of two polarization preserving fibers have their ends oriented into a position to locate the respective axes at 45 degrees. A fusion splicer and a heating controller for the fiber sensing coil are added to a reciprocal interferometer to produce a predetermined pattern of percent light intensity versus time in the returned light, when the axes are properly aligned for fusing. A computer may control the automatic making of depolarizers by this invention.

Fiber depolarizer using heated fiber coil and fusion splicer and two

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.

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Wrightwood, CA, United States of America

Ronald James Michal