Page 212 - Optical Switching And Networking Handbook

09_200023_CH08/Batesx 1/17/01 8:20 AM Page 197

High-Speed Applications 197

can be sustained on such a local feed. At the incumbent local
exchange carrier (ILEC) (or competitive local exchange carrier
[CLEC]) office, a digital cross-connect system will bundle the access
lines together onto a SONET/SDH channel at OC-1, OC-3/STM-1,
OC-12/STM-4, or higher. This is shown in Figure 8-10, where the
local loop is still copper, but fiber services are applied at the ILEC
office. An alternative to the copper feed is the possibility that the
local exchange carrier (LEC) may have a digital subscriber loop,
using fiber on what it calls the digital loop carrier (DLC). In this
case, the fiber enables higher-speed access.
Another possibility, shown in Figure 8-11, is the use of integrated
access services. The customer may choose to install a DS-3 (T-3) to
the door to support the following services:
Voice at the PBX, which may be using one or more T-1s

LAN using a 10-Mbps feed from an Ethernet router
Other data services

Figure 8-10
Looking outward INTERNET
from the
consumer’s door Ethernet LAN
Core Router
Workstation
Digital Cross Connect

MDF
OC-12
Server Fiber
Access Node
Access
Router ILEC Central Office

Conditioned ILEC SLC (or DLC)
Circuit
Copper Loop