5
Wire, Fiber, Cable, and Wireless Access
More than one hundred and sixty years ago, telegraph companies began to use wires to connect their message stations. More than one hundred and thirty years ago, telcos began to use wires to carry analog voice signals to their subscribers. Today, in multipair cables that permeate all urban, suburban, and rural communities, a substantial fraction of the world’s copper supply has been consumed by the telecommunications industry. Most of it is found in outside plant facilities. Depending on the sophistication of the service provider, today’s connections between customers and end offices or head ends are realized with wires, optical fibers, cables, and wireless. Individual users expect the connections to carry signals that range from voice over IP to high-definition television and high-speed Internet. Delivering these services is best accomplished if the access transport is digital and packet-based.
Figure 5.1 shows some of the connections that are found in wired/fiber/cable/wireless access networks. The connections range from voice over twisted-pairs, to wideband digital subscriber lines (DSLs) over twisted pairs or twisted pairs and fiber, to passive optical networks (PONs) over fiber, to broadband systems over coaxial cables or fibers, and multimedia systems over wireless. It should be noted that the wire, fiber, and wireless systems employed by telcos and cellcos mostly forward only the channels the customer wishes to use; this differs from ...
