Agilent Technologies, Inc.

Georgia Tech Research Corporation

Gregory D Van Wiggeren

Thomas K Gaylord

Elias N Glytsis

Emmanuel Anemogiannis

Donald D Davis

Douglas Michael Baney

Ali R Motamedi

The present invention relates to a type of optical fiber grating having an azimuthal refractive-index perturbation. The optical fiber includes a fiber grating that has a plurality of grating elements formed therein. At least one of the grating elements has a spatially varying index of refraction that varies azimuthally about the centerline of the optical fiber. The fiber grating acts as a band-stop optical spectral filter. In addition, since fiber-cladding modes are weakly-guided modes, their power can be easily dissipated by scattering, bending, stretching, and/or rotating the optical fiber. Multiple configurations of these gratings within an optical fiber are given. Methodologies are given for the fabrication of these gratings. Devices are presented which can dynamically attenuate, tune, switch, or modulate the wavelength spectral characteristics of an optical signal.

Optical fiber gratings with azimuthal refractive index perturbation

Phase noise is at least partially cancelled for an interferometric system by using a delay/phase cross-correlation approach for two interferometers within the system. The cross-correlation approach may be used in measuring group delay of a device under test and includes determining the differences between the phase of the output of each interferometer at time t and the phase of the same output at the time t minus the delay of the other interferometer. In one embodiment, the first phase difference is the difference between the phase of a test interferometer output at time t and the phase of the test interferometer output at the time t offset by the known delay of a reference interferometer. The second phase difference is calculated using the same technique, but the time offset is a delay representative of the relative delay of two light propagations within the test interferometer. A noise-cancelled time series output that is indicative of group delay can then be generated by determining the difference between the first and second differences.

Phase noise compensation in an interferometric system

Optical fiber gratings with azimuthal refractive index perturbation, method of fabrication, and devices for tuning, attenuating, switching, and modulating optical signals

In the measurements of optical characteristics, such as measurements of group delay using an interferometric system, vibration noise can be at least partially offset by providing corrections on the basis of detecting light patterns that are indicative of the vibration noise. In each embodiment, light beams propagating through first and second paths are combined to form an interference signal, which is analyzed to provide the basis for the adjustments.

Vibration noise mitigation in an interferometric system

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Los Gatos, CA, United States of America

Gregory D Van Wiggeren