Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A method for forming an all-fiber, low-loss interleaver to obtain a predetermined optical channel spacing. The interleaver features at least one arm formed with and continuous between couplers of a Mach Zender type arrangement. The interleaver is formed by first analytically determining &Dgr;&thgr;, the difference in optical lengths between the two optical paths between the couplers. The difference is then fine-tuned by the application of heat and tension to a jacket-stripped segment of the continuous fiber arm as a DWDM signal is observed at the output of the interleaver.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: An optical instrument is provided which can be configured as a gyro, spectrometer, or other sensor of effects that can influence the transmission of light through a light conduit wherein a beam of light is split and introduced into both ends of an optical fiber which in the gyro case is a fiber-optic coil. Two fixed frequency shifters and two variable frequency shifters, one each at each end of the coil, which are switched on in alternate pairs, are used to adjust any nonreciprocal phase shift caused by rotation of the coil. The beams are mixed backed together and the resultant beam is detected and analyzed by suitable circuitry to provide an output indicative of the angular position, direction of rotation, and angular rate of the motion of the fiber-optic coil as well as any frequency bias and scale factor changes. When configured as a spectrometer, the coil is made insensitive to rotation so that changes are the result of changes in the light source.

Abstract: There is provided by this invention an optical sensing system utilizing a Sagnac interferometer having a frequency shifter within the Sagnac counterpropagating loop that is generally comprised of a plurality of acoustic transducers mounted on acousto-optical material to frequency shift and beamsplit a light beam simultaneously within the material while at the same time having the capability of switching between an upshifted or downshifted frequency in either a Bragg or Raman-Nath mode of operation without realigning the optical beams. The acousto-optical material has a special configuration to eliminate back reflections of the acoustic waves that can interact with the light beam. In addition, special alignment of the transducers with dampening configurations also serves to prevent back reflections of the acoustic wave from interacting with the light beam.

Abstract: There is provided a fiber optic sensor for sensing environmental effects on counterpropagating light beams in an optical loop by comparing the modulation of the light beams in an optical coil exposed to the environmental effects and comparison with a reference fiber shielded from the environmental effects. The counterpropagating light paths contain optical phase modulators for creating nonreciprocal phase shifts and may comprise elongated sections forming a long line array.