o as enabling mesh capability in the optical network.) These optical networks are comprised of DWDM systems connected to intelligent optical crossconnects (OXCs). OXCs encompass the essential functions of SONET/SDH equipment, including restoration, signaling, per- formance monitoring, fault management, and multiplexing. Traditional SONET/SDH equipment is pushed even further to the edge of the network to manage the lower-speed interfaces and mixtures of protocols. This enables the core optical network to handle the high-speed traffic, which makes the core easy to build and manage. It is worth noting that the traditional SONET/SDH protocol is still used in the network, only in a different way. The traditional OAM&P features are required by carriers and are performed in an efficient manner by SONET network elements (NEs). The goal of the OXC is to remove the expensive SONET/SDH equipment layer, but not the protocol itself. Another benefit of OXCs is that they support mesh architectures. A mesh network enables the Traditional SONET Architectures Figure 3-3 Third-Generation Optical Network Third-generation optical network. SONET SONET switch switch Shared Fiber Protection Link SONET SONET switch switch Working Fiber Connection = Optical Crossconnect restoration capacity (protecting fiber) to be shared across the various spans and nodes in the network. Figure 3-3 shows that utilizing a mesh architec- ture lowers the amount of capacity used for protecting the network, reduc- ing the cost of redundancy and resilience. 3 Third-generation networks are currently being tested in the market- place. A key feature of this network is that it has the potential to handle data rates up to 40 Gbps (OC-768) and beyond. Again, because of cost, the ideal application for this technology is still long haul. Although equipment cost is important, it tends to be only 10 to 15 per- cent of the total cost incurred by a carrier and reflected in the service charges. Hence, equipment cost reduction is important, but its overall true effect has t