-to-point system may be enhanced through a geographically diverse protection path (see Figure 3-33). Where diverse routing exceeds the normal reach of the transport sys- tem, one or more regenerators or optical amplifiers can be deployed to reconstitute (or boost) the optical signal. 1:N Protection Channel Sharing This is a multinetwork element point-to-point configuration that conserves fiber pairs by enabling multiple systems to share a common protection channel. In applications with rapidly growing traffic demand, the 1:N protection arrangement can defer, or avoid altogether, the large capital outlays and long lead times associated with the deployment of new fiber cable. If a failure or degradation occurs on any working optical channel, the affected traffic is automatically rerouted over the protection channel via an intershelf protection loop and a dedicated protection shelf at each end of the span (see Figure 3-34). 14 Each working shelf can be equipped with a full complement of mixed electrical and optical tributary types. If desired, the 1:N protection configuration's protection shelves and the normally empty protection bandwidth may be exploited to transport unpro- tected extra traffic. Linear ADM Linear ADM configuration provides direct access to indi- vidual eastbound or westbound VT/STS channels at intermediate sites along a fiber route-without the unnecessary multiplexing/demultiplexing "Classic" Point-to-Point Configuration Figure 3-33 Point-to-Point Point-to-point systems Terminal 1 + 1/1:1 Protected Fiber Span with and without router diversity. Mixed Tributaries Point-to-Point Configuration with Route Diversity Diverse Route Protection Path Regenerator or Optical Amplifiers Traditional SONET Architectures Extra Traffic Extra Traffic Figure 3-34 Shared OC-48 Protection Channel 1:N protection channel sharing configuration- OC-48 Protection Shelves Nortel's S/DMS Mixed Mixed TransportNode OC- Tributaries Tributaries 48 application is shown. OC-48 Working Channel 1 Mixed OC-48 Terminal Shelves for Mixe