Accession Number : AD0710946

Title :   AN INFORMATION FEEDBACK APPROACH APPLIED TO AN AMPLITUDE-MODULATED DIGITAL LASER COMMUNICATIONS SYSTEM.

Descriptive Note : Technical rept.,

Corporate Author : ARMY ELECTRONICS COMMAND FORT MONMOUTH N J

Personal Author(s) : Dworkin,Larry U.

Report Date : MAR 1970

Pagination or Media Count : 97

Abstract : The use of predecision feedback in a laser communication system employing an amplitude-modulated laser transmitter and photomultiplier receiver is considered. Poisson statistics are used to describe the distribution of emitted photo electrons in a fixed time interval from the photo emissive surface of the receiver when the incident field is a mixture of a single mode laser and broadband thermal noise. The use of a noiseless feedback path to reduce the variance of the received photo electron count is examined. A technique known as 'feedback averaging' is conceived and the following properties are demonstrated. (a) The variance of the received photo electron counts is significantly reduced over that obtained in a system without feedback. (b) The effects of background radiation and shot noise at the receiver can be reduced. (c) The effect of slow fading on the mean arrival rate of photons is reduced. This is achieved in the above system with the same average power and only slightly more peak power, in most cases, than the same system without feedback. The approach is treated analytically, and simulated on a digital computer. (Author)

Descriptors :   (*OPTICAL COMMUNICATIONS, FEEDBACK), DIGITAL SYSTEMS, DIGITAL COMPUTERS, AMPLITUDE MODULATION, INFORMATION THEORY, MONTE CARLO METHOD, LASERS, PHOTONS, COUNT RATE METERS, ATTENUATION

Subject Categories : Lasers and Masers
      Non-radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE