AUTOMATIC GAIN CONTROL FOR FREE-SPACE OPTICAL TELECOMMUNICATIONS LINKS

摘要

Free-space optical transmission of analog information is facilitated by transmitting constant-amplitude pilot information with the other information. Th e amount of attenuation of the pilot information at the receiver is detected and used to control the amount by which received information is amplified. In this way the deleterious e ffects of free-space optical attenuation are substantially eliminated. The pilot informati on may be transmitted either via its own separate light frequency or wavelength, or as a distinguishable part of a larger quantity of information that is used to modulat e one light frequency or wavelength.