Lucent Technologies Inc.

Alcatel-lucent USA Inc.

Dennis M Romain

Steven R Johnson

Gerald Nykolak

Richard Robert Shively

Paul F Szajowski

Alex Pidwerbetsky

Marc J Beacken

Howard David Helms

Robert D Trachtenberg

Dominick J Imbesi

A method for target acquisition and tracking of a moving station or target (e.g., an unmanned aerial vehicle) for carrying out free space optical communications uses an 'elapsed time'-based approach to determine the position of the moving station at any future time, based on the time difference since the moving station's last known position. For example, the vehicle may be for purposes of reconnaissance, where the optical link provides a secure and high-bandwidth communications pathway between the moving station and a ground station. A mathematical model of the moving station's expected periodic flight path is combined with position and time elements to accurately predict the future position of the moving station for target re-acquisition. The model is a cubic spline interpolation of known flight path waypoints. The system may also employ multiple waypoints in initial acquisition, by alternating acquisition attempts over several waypoints instead of 'staring' at a single waypoint.

Method and system for tracking a moving station or target in free space communications

A process and apparatus is described for recovering from optical transmission degradation due to scintillation effects in optical free space. A payload bit stream is encoded into Reed-Solomon codewords. These are fragmented and distributed as interleaved segments over a cell matrix of a SDRAM buffer store which is made large enough to correct a burst error occurring over 20 million consecutive bits. The rate imbalance between conventional read vs. write operations for SDRAM devices, which would otherwise obviate their use in this application by preventing real time operation, is overcome by an address remapping that avoids having to changing page addresses each time SDRAM memory is referenced. The remapping facilitates a more nearly equal allocation of READ overhead and WRITE overhead. An optical communications system employs at both the transmit and receive ends, substantially equivalent SDRAM buffer with address remapping capability.

Reducing scintillation effects for optical free-space transmission

In the method and apparatus for controlling the power level of a laser signal in free space communication, a communication terminal transmits an output laser beam into free space and also receives information, through a channel that is not free space laser based, about the power of the output laser beam measured at a distance and at different times. The terminal determines whether a drop in the power of the output laser beam measured at the distance is due to atmospheric effects based on the received information. The terminal increases the power level of the output laser beam to a desired level if the power drop is determined to be due to atmospheric effects. On the other hand, the terminal lowers the power of the output laser beam to a predetermined level if the power drop is determined to be due to blockage thus avoiding harm to accidental observers that might intrude into the path of the laser beams.

Method and apparatus for controlling signal power level in free space communication

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Morristown, NJ, United States of America

Dennis M Romain