Wednesday, October 01, 2008

Free space laser communication

Lasers have been considered for space communication since their realization in 1960. It was soon recognized that, although the laser had potential for the transfer data at potentially high rates.
Features of laser communication
Extremely high bandwidth and large information throughput available many times greater than RF communication. Modulation of helium-Neon laser (frequency 4.7 x 1014) results in a channel bandwidth of 4700 GHz, which is enough to carry a million simultaneous TV channel.
Small antenna size requires only a small increase in weight and volume of the satellite. This reduces blockage of fields of view of most desirable areas on satellites. Laser satellite communication equipment can provide advantages of 3:1 in mass and 2:1 in power relative to microwave systemsNarrow beam divergence affords interference free and secure operation. The existence of laser beams cannot be detected with spectrum analyzers. Antenna gain made possible by narrow beam, enables small telescope aperture to be used. The 1550nm-wavelength technology has added the advantage of being inherently eye-safe at the power levels used in the free space systems, alleviating the health and safety concerns often raised with using lasers in an open environment where human exposure is possible.Laser technology can meet the needs of a variety of space missions, including intersatellite links, Earth to near-space links, and deep space missions. The vast distances to deep space make data return via conventional radio frequency techniques extremely difficult.

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