Concurrently, the carriers are enhancing network survivability and accommodating escalating demand for services such as video, high-resolution graphics, and large-volume data processing. Each application requires insatiable amounts of bandwidth. Frame Relay and ATM also add to the demand. Internet usage, which is growing by 100 percent annually, is threatening to overwhelm access networks.

Over the past 20 years, the telecommunications infrastructure has been migrating to massive computerization and extensive use of fiberoptic cables. The widespread use of fiber has been made possible, in part, by the industry s acceptance of SONET and SDH as the standards for signal generation. Using SONET/SDH standards, telephone companies gradually expanded capacity by increasing data rates to 2.488 to 10 Gbps.