Diasense, Inc.

General Electric Company

Itt Manufacturing Enterprises, Inc.

Exelis Inc.

Dean S Grinch

James A Cunningham

Ajith Kuttannair Kumar

Daniel L Baber

Herbert J Brown

Ronald F Griebel

Stuart W McElhenny

Donald Fisher

Augustyn Waczynski

Richard L Wiggins

David R Wickholm

John S Mazurowski

David Wickholm

Donald Scott Fisher

A technique for simultaneously transmitting wide and narrow optical beacon signals includes generating a laser beam and splitting the laser beam into a first signal on a first path and a second signal on a second path via a wavelength-dependent beamsplitter. A wide beacon signal having a first beam divergence is generated from the first signal, and a narrow beacon signal having a second, lesser beam divergence is generated from the second signal. The wavelength of the laser beam determines an allocation of the laser energy between the wide and narrow beacon signals based on transmittance/reflectance characteristic of the beamsplitter at that wavelength. The wide and narrow beacon signals are simultaneously transmitted in a overlaid manner into free space to support acquisition and tracking in a free-space optical communication system. The beamsplitter can simultaneously transmit or reflect substantially all of a data signal at a different wavelength.

Technique for simultaneously transmitting wide and narrow optical beacon signals

A technique for acquiring and tracking terminals in a free-space laser communication system involves exchanging beacon laser beams between the terminals to acquire and then track the terminals such that data laser beams exchanged by the terminals for communication are steered based on feedback from detection of the beacon laser beams. The beacon laser beams used for acquisition have a greater beam divergence than those used for tracking. Gimbals provide coarse steering of the data laser beams, and steering mirrors provide fine steering. GPS position data exchanged via an RF link can be used for initial pointing of the beacon laser beams for acquisition. The beacon laser beams can be chopped such that all terminals can use the same beacon wavelength and are distinguished by using different chopping frequencies. By detecting a chopped signal, the position sensor detector can be AC coupled to reduce sensitivity to solar radiation and glint.

Acquisition, pointing, and tracking architecture for laser communication

Biasing arrangement for linear detector array

A method for accurately converting to an electrical signal a modulated optical signal, the modulation frequency of which randomly varies in a narrow range about a predefined optimum modulation frequency, includes the steps of receiving the optical signal at an optical detector, producing as an output of the optical detector an electrical signal corresponding to the optical signal, the amplitude of which electrical signal varies with frequency, and modifying the amplitude of the electrical signal, depending on the frequency of the electrical signal, inversely to the variation of the amplitude of the electrical signal with frequency caused by the optical detector.

Method and apparatus for converting a modulated optical signal to an

In an electrical propulsion system on board a moving traction vehicle (such as a rapid transit rail car) having current collectors in contact with an energized third rail, controllable switch means is used to connect the system to the current collectors. From time to time the current collectors traverse gaps between adjacent sections of the third rail, in which event regenerative braking operation of the system will be prevented unless the next third rail section is energized by a wayside source of voltage. The switch means comprises the parallel combination of a diode that conducts current when the system is operating in a motoring mode and a reversely-poled thyristor that conducts regenerative braking current once a firing signal is applied thereto. To detect the energized status of the third rail, an electrical filter network is excited by the third rail voltage and derives an output value representative of the amplitude of an a-c ripple component of such voltage having a fundamental frequency that characterizes the wayside voltage source, and after each third rail gap is traversed a firing signal is applied to the thyristor as soon as this value exceeds a predetermined minimum level.

Regenerative braking protection for an electrically-propelled traction

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Dublin, OH, United States of America

Dean S Grinch