Key elements of high-speed WDM terrestrial free-space optical communications systems

ABSTRACT Terrestrialfree-space optical communication systems operating in WDM configurations @2. 5Gb/s per channel, have been shown to provide a viable means to transport data, voiceand video channels forfiber-less point-to-point applications. Key design features of free-space optical transmission systems are their ability to utilize present day telecommunication components such as; laser diode transmitters, high-power optical amplflers within the 1550nm optical window and high-sensitivity optical receivers 2.5Gb/s together withtelescope terminals. This paper presents key operational elements which impact upon performance characteristics for terrestrialfree-space laser communications systems within the 1550nmwindow. These elements include; optical transmit and receivefunctionality ofthe telescope terminals, electro-optic components as well as atmospheric conditions affecting link performance.1. INTRODUCTION Experimental transmission system results for a single-channel 1 550nm free-space optical data-link operating @2.5Gb/s over a 2.4km transmission span has been reported.' A four-channel WDM 1550nm, 4.4 km free-spaceoptical data link operating @ 10 Gb/s has also been reported as well as details and results, modeling system opticalmargin, range and availability capabilities for 1, 2, 4, and 8 transmission channels at 2.5Gb/s under various visibilityconditions.2'3 Using optical margin estimates system availability was reported for four metropolitan locations undervarious visibility conditions.3 Modeling system performance, utilizing free-space optical data-link components