ments there are-including WDM/DWDM/ CWDM, OADMs, ROADMs, optical cross-connects, and optical switches-the more difficult the job. Also, as the number of wavelengths grows, there has to be a facility to monitor and manage each one of them. Of course, the ability to provi- The Optical Edge sion services quickly is also a key requirement, and a proper network management system can help providers not only manage their own networks efficiently but also offer end-to-end managed wavelength service. The Optical Edge Today, SDH/SONET channels are used for voice and time-division-multiplexed private-line traffic where the equipment typically involves ADMs and digital cross- connects (see Figure 11.11). Optical networks today are also used to support Layer 2 services, such as ATM, Frame Relay, and Ethernet, and switch equipment. In addi- tion, they are used to support Layer 3 services, such as routed IP; IP routers are the most typical equipment type at Layer 3. Vast changes are occurring at the optical edge. As discussed in the following sections, three categories of optical access products (i.e., specialized access equip- ment) are being introduced at the optical edge: next-generation digital loop carrier systems, PONs, and MSPPs. Next-Generation Digital Loop Carriers The main feature of a next-generation digital loop carrier is its support for SDH/ SONET fiber as well as copper connections to the local exchange. These devices allow the integration of DSL modem support without requiring the installation of DSL access multiplexers (DSLAMs). In other words, the DSLAM functionality built into the next-generation digital loop carrier. Also, the new digital loop carri- ers can support ATM multiplexing for DSL services along with the traditional TDM ATM Switch Digital Cross-Connect SDH/SONET SDH/SONET Optical IP Router Optical Circuit Switch Private Lines Voice Switch Figure 11.11 The optical edge Chapter 11 Optical Networking interfaces for voice. Voice channels are multiplexed in the traditional TDM style and sent over the PS