Last month, we looked at how dark fiber is tested to determine its capability of supporting newer, faster transmission networks. Once dark fiber has been tested and its usability confirmed, communications systems can be connected.
Generally, metropolitan and long-distance networks using dark fiber are quite different from the systems common to customer-owned premises cabling. Premises cabling used for local-area networks (LANs) or security systems generally are based on multimode fiber and require two fibers dedicated to every link. Two fibers are used to provide full duplex operation, with each fiber transmitting in opposite directions