Georgia Tech Research Corporation

Furukawa Electric North America, Inc.

Ming Yang

William Alfred Reed

Alice Weimin Liu

Andrew Ingles, Jr

Peng Wang

Jacek Jarzynski

Yves H Berthelot

A system and technique for determining discontinuities over a span of a multimode optical fiber (MMF). An optical time domain reflectometer (OTDR) has an operating port, and a first end face of a singlemode optical fiber (SMF) is coupled to the operating port. Light pulses produced by the OTDR emerge from a second end face of the SMF, and an alignment stage aligns the second end face with an end face of a multimode optical fiber (MMF) having a core of given radius. The light pulses from the second end face of the SMF are applied at selected radial positions on the MMF core to excite corresponding mode groups in the MMF. Backscatter light produced by each excited mode group is coupled to the OTDR through the SMF. Locations and values of events detected along the MMF are indicated on the OTDR for each selected radial position.

Detection of discontinuities in a multimode optical fiber

A method of detecting and measuring separately the components of vector dynamics on the surface of a vibrating object comprises directing three beams of coherent light onto a common spot on the surface. Each of these beams has a known optical frequency. Two are arranged symmetrically about a normal to the surface at the point of incidence and the third is arranged asymmetrically about the normal with respect to both the first and second beams. Superposition of each beam with the others on the surface produces scattered light embodying characteristic beat or carrier signals equal to the difference in frequencies between the beams. Vector dynamics including velocity and displacement of the vibrating surface induces Doppler shifts in the beams, which, in turn results in a modulation of the carrier frequencies resulting from the superposition of the beams. Each carrier frequency is then isolated and demodulated to produce a signal corresponding to various components of the vector dynamics on the surface that cause the modulation. Further analysis extracts information about the frequency and magnitude of resolved vector dynamics on the surface. The method can be applied at several locations on the object's surface to determine vector dynamics at several points simultaneously.

Method and apparatus for detecting surface wave vector dynamics using

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Ming Yang