pects. The chapter wraps up by analyzing the future of FSO. The global telecommunications networking environment has undergone unprecedented growth over the past several years, which was fueled by the telecommunications deregulation in 1996.¹ Since 1996, service providers have spent an enormous amount of capital investment on building long- haul WAN infrastructures such as Frame Relay, Asynchronous Transfer Mode (ATM), and Internet Protocol (IP) networks. In the past two years, emphasis has been put on MANs due to the increasing telecommunications traffic demand in densely populated metropolitan cities. In order to enable end users (that is, corporate users) to access these long-haul WANs and MANs, network designers must provide them with a broad array of flexible access solutions that operate in a cost-effective manner. Even today, a vast majority of local-loop connections (sometimes referred to as first mile or last mile) are still limited to T1 line speed, and consequently, there is a definite need for utilizing an access technology that will bridge the gap between a LAN and MAN as well as between a LAN and WAN. Optical wireless sys- tems (FSOs) represent an approach for addressing and possibly solving the first-mile and last-mile bottleneck. Figure 9-1 depicts the bandwidth capa- bilities of various transmission media. Optical wireless systems transport high-speed data through the air on light beams transmitted by highly focused lasers. These lasers are often installed on building rooftops and windows. This emerging technology has now matured to a stage where a noticeable group of equipment vendors have introduced their own FSO products for various applications. Some of the most promising features for using FSO as an access solution include the ease of network deployment, low startup and operating costs, fiber-like bandwidth, and no requirement for an operating license. Commercially available systems can offer capacities ranging from 100 Mbps to OC-48 (2.5 Gbps) and beta systems operating at data rates as hig