Having made its mark on intersatellite, satellite-ground and satellite-submarine links in the 60's and 70's, optical wireless communications (OWC) is fast becoming a feature of urban terrestrial communications. There is an ever-increasing demand for high-speed data transmission with growing use of internet applications, multimedia and company intranet. Optic fiber can provide datarates of tens of gigabits/second, but, while the fiber backbone reaches most major cities in the world, less than 10% of end-users have fiber connection. As a consequence, a major bottleneck restricts communication over what is termed "the last mile" [1]. Possible solutions include laying optic fiber, which requires nigh capital investment and is often not possible due to the disruption involved (digging up roads, etc), transducing the data for copper wire transport, which necessitates relinquishing the high datarate as well as leasing costs, and, thirdly, transmitting the information wirelessly. Radio frequencies carry heavy tariffs and licensing fees, so installment is a lengthy beaurocratic process as well being expensive. Communication bandwidths are also less than for optical carriers. In contrast, OWC offers the same bandwidths as optic fiber, is not restricted by licensing, is very rapidly deployable and uses low power consumption, small, compact equipment. However, two main disadvantages hamper the widespread application on OWC; the demand for strict transmitter-receiver alignment and the severe degradation of signals in adverse weather conditions. The most deleterious weather condition is fog, which is the cause of multiple scattering. This phenomenon results in spatial, angular and temporal spread. Light reaching the receiver aperture within its spatial dimensions is detected on condition that the angular spread is within the restrictions of the field of view (FOV) setting. Increasing the FOV facilitates the reception of more signal power, but at the cost of increased noise power. In this paper we use Monte-Carlo methods to study the passage of light through fog and evaluate the possibilities of enhancing OWC performance by adaptively changing the FOV. The FOV is increased by selectively activating detectors in an array, and the signal and noise powers for different settings are computed. The WDM C-band range of wavelengths was investigated as they facilitate seamless fiber-wireless communication and since eye-safety regulations sanction higher power transmission than for near infrared wavelengths [2]. Power reception improvements of tens of percent, by comparison to the use of a single detector, are demonstrated. In a numerical example, this is translated into BER improvements of several orders of magnitude.
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