Design of the high-speed framing, FEC, and interleaving hardware used in a 5.4km free-space optical communication experiment

Abstract

The forward error correction (FEC) and interleaver realizations used in a 5.4 km horizontal-path link experiment incorporated several unique elements that were specifically tailored to address turbulence-induced fading. To facilitate optimization studies, this hardware was designed to afford a high degree of flexibility in the FEC code structure and interleaver length. An essential aspect of this structure was the standards-compliant client interface, which provided seamless connectivity to fiber-based terrestrial networks. Through the use of an OTU1 (2.667 Gbaud) architecture with nonstandard interleaving, error-free transmission was achieved in the presence of strong scintillation that produced fade events that frequently exceeded 10 ms in duration. This work was sponsored by the Department of Defense, RRCO DDR&E, under Air Force Contract FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Government.