Backscattering-induced crosstalk in WDM optical wireless communication

The crosstalk effect of aerosol backscatter on the performance of a wavelength-division-multiplexed (WDM) optical wireless communication (OWC) system is investigated, analyzed, and quantified. An OWC link could be a segment within a metropolitan area network (MAN) or a ground-station-to-space link of a satellite communication system. In these cases, a WDM transmitter and receiver are housed in one transceiver unit with parallel, or near-parallel, optic axes. The crosstalk at the receiver is caused by light from the transmitted signal of the same transceiver, which has been backscattered by molecules and aerosols in the atmosphere. This is exacerbated in the presence of fog and haze, in which case both the desired signal from another transceiver is attenuated by scattering and the backscatter-induced crosstalk increases. A bit-error-rate (BER) model is derived that takes into consideration the dominant noise sources, including backscatter-induced crosstalk and signal mixing with amplified stimulated emission (ASE) from an optical preamplifier at the receiver. The numerical calculations in this paper indicate that, in moderate fog, the BER may increase by an order of magnitude or more due to backscatter, depending upon the atmospheric extinction coefficient.