Highly Reliable High-Capacity Free-space Optical Communication with Partially Coherent Beams

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Schematic setup providing for generation of partially coherent beams by using phase screensSchematic setup providing for generation of partially coherent beams by using reflectors
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Aristide Dogariu, Ph.D.
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John Miner
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Free-space optical communications with partially coherent beams

US Patent 6,807,375 B2
Publications
Long-distance Propagation of Partially Coherent Beams through Atmospheric Turbulence
Science Direct, Dec. 2002

A communication system and methods of transmitting and receiving sensitive data from a laser source through a non-confined optical free-space by providing a stable connection even under adverse atmospheric conditions

UCF engineers and scientists have developed a novel free-space optical communication system using a laser beam for transmitting data by means of partially coherent optical energy. The invention has high directionality and focus, and thus provides stable freespace optical communications even under the most adverse atmospheric conditions. Beams produced by sources of lower spectral coherence are more stable, namely because they are less affected by changes in the atmospheric conditions, therefore partially coherent beams are a great choice for use in any long path propagation scheme such as in the use of communication systems. Moreover, this invention provides an optical communication means that is clearly superior to any known optical free-space transmission system.

Technical Details

Laying optical fiber in order to provide broadband access to congested urban areas as well as to remote regions is a difficult task. Free-space optics (FSO), also known as optical wireless, overcomes this “last-mile” access bottleneck by sending high-bitrate signals through the air using laser transmission. This technology has matured to meet the growing demand of higher data transmission to and from aircraft, satellites and mobile devices. The main draw-back of free space optical communication is the fact that light beams propagating over long distances can be affected by adverse conditions. Although relatively unaffected by rain and snow, fog and atmospheric turbulence can seriously impact free-space optical communication systems. These air pockets act like lenses with time-varying properties and can lead to sharp increases in the bit-error-rates, particularly in the presence of direct sunlight. Such conditions cause optical phase perturbations that destroy the spatial coherence of a laser beam as it propagates through the atmosphere. As a result, the distances over which optical communications can be operated are limited and performance is diminished.

Benefits

  • Provides a reliable communication that is easy to install, easy to operate, and has increased data network capacity
  • Allows for the transmission of data without the need for spectrum licensing
  • Uses a point-to-point laser signal that is extremely difficult to intercept, making it ideal for covert communications

Applications

  • Light or radar detection and ranging (LIDAR and LADAR) to determine information from a distant object
  • Communication companies
  • Fiber-less optical networks for high speed data networking