PDF of this tutorialAll-fiber access systems consisting of SONET or SDH fiber rings are commonly used to provide high-capacity, multiservices (including Internet) access to and from campus and business locations. SONET is a North American–based standard for such an architecture with interface rates from 1.544 Mbps (DS–1) to 10 Gbps (OC–192). Similarly, SDH is the European-based standard for equipment with similar capabilities.
The bottom portion of Figure 10 shows a SONET/SDH connection from a service node to a business. The SONET/SDH ring provides service assurance via path-diversity ring architecture. In a campus environment, the ring could be extended through the various buildings that make up the campus.
Figure 10. Pure Fiber Access—SONET
On the customer premises, the customer's intranet, depicted by the local-area network (LAN), is connected to the public network via a firewall. The firewall provides data and security protection for the business. Firewalls provide security by isolating undesired Internet traffic from the traffic that is carried on intranet LANs. Multiplexers (Mux) provide transport efficiency by combining separate data streams onto a single fiber-optic facility. Synchronous transfer mode (STM) multiplexers widely deployed in telecommunications networks carry data streams within discrete tributaries. Asynchronous transfer mode (ATM) multiplexers can provide more interface-rate granularity because individual user data streams are concatenated into a single high-speed cell stream for transport within the network. In addition, ATM multiplexers can provide further efficiency by combining variable-rate data streams using statistical multiplexing.
