PROCEEDINGS ARTICLE | August 29, 2002
Proc. SPIE. 4905, Materials and Devices for Optical and Wireless Communications
KEYWORDS: Diffraction, Mirrors, Holograms, Holography, Crystals, Wavefronts, Atmospheric corrections, Liquid crystals, Laser communications, Atmospheric optics
A laser beam propagating through the atmosphere, undergoes attenuation through absorption and scattering on droplets of fog, clouds, different kinds of precipitation (rain, snow), smoke, dust; as well as it is subjected to a turbulence-induced scintillation. The resulting influence is a decrease of the information capacity of the system, rise of the bit-error rate and deterioration of the pointing accuracy at the receiver. Whereas the attenuation caused by scattering can be predicted by monitoring the weather conditions, the effects induced by turbulence have a random character and need to be overcome via some dynamic compensation procedure. This can be done using the phenomenon of wavefront reversal by means of dynamic holograms, which allows automatic compensation of disturbances. The unique advantages given by holographic technique make it rather promising to develop a relatively simple and reliable module for correction of atmospheric distortions in laser communication systems. One of the main problems though is to find an optimal medium for hologram recording that allows fast write-read-erase operation, high diffraction efficiency, high stability of characteristics and long lifetime.
