Open AccessCapacity of coherent free-space optical links using diversity-combining techniques
Author(s) -
Aniceto Belmonte,
Joseph M. Kahn
Publication year - 2009
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.17.012601
Subject(s) - optics , free space optical communication , fading , physics , diversity combining , signal to noise ratio (imaging) , wavefront , local oscillator , antenna diversity , coherence (philosophical gambling strategy) , aperture (computer memory) , optical communication , computer science , phase noise , telecommunications , channel (broadcasting) , antenna (radio) , acoustics , quantum mechanics
We study the performance of diversity combining techniques applied to synchronous laser communication through the turbulent atmosphere. We assume that a single information-bearing signal is transmitted over two or more statistically independent fading channels, and that the multiple replicas are combined at the receiver to improve detection efficiency. We consider the effects of log-normal amplitude fluctuations and Gaussian phase fluctuations, in addition to local oscillator shot noise. We study the effect of various parameters, including the ratio of receiver aperture diameter to wavefront coherence diameter, the scintillation index, and the number of independent diversity branches combined at the receiver. We consider both maximal-ratio combining (MRC) and selective combining (SC) diversity schemes. We derive expressions for the outage Shannon capacity, thus placing upper bounds on the spectral efficiency achievable using these techniques.