In the local loop, carriers have installed fiber to carry multiplexed signal streams close to their destination. They terminate in optical network interfaces (ONIs) where twisted pairs are used to complete the connection to residences or small businesses. Several acronyms are used to identify such installations: ã FITL: fiber in the loop; ã FTTC: fiber to the curb; ã FTTH: fiber to the home. They are used without precision to indicate various levels of fiber availability. Most carriers are awaiting the development of demand for residential wideband services before making major commitments to these facilities. SONET rings are employed to connect the main switching center, remote switches, remote terminals, distribution interfaces, and other traffic collection points. Figure 8.2 illustrates the principle of applying SONET in the local communication environment to replace feeder cables. In the figure, a star-star arrangement is compared to ring-based structures that employ SONETs. The ring-bus structure is constructed from the combination of cable television and incumbent local exchange