Backscatter-induced crosstalk interference in urban optical wireless communication

In this paper we summarize work done on the crosstalk effect of aerosol backscatter on the performance of an urban optical wireless communication (UOWC) system. The communication link is a segment within a metropolitan area network (MAN), where 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, when both the desired signal from another transceiver is attenuated by scattering and the backscatter-induced crosstalk increases. In our research we derive a bit error rate (BER) model which takes into consideration the dominant noise sources, which include the backscatter-induced crosstalk and the signal mixing with amplified stimulated emission (ASE) from an optical pre-amplifier at the receiver. Our numerical calculations indicate that in a moderate fog the BER may increase by an order of magnitude, due to backscatter.