t of these operations is that the ring is now wrapped and all nodes are connected. 6.4.2 BWDM Applications In a wide area network (WAN) environment with limited fiber availability, BWDM presents a solution for SRP ring deployment or PoS connectivity. In Figure 6-15, BWDM technology enables an SRP ring to be deployed using the existing point-to-point infrastructure (between locations A and B and between C and D). As shown previously, BWDM-based SRP rings are as resilient as traditional SRP rings. Furthermore, using the BWDM-equipped concentrator to deploy SRP rings provides many advantages such as E-IPS, ring management, maintenance with no service interruption, and more simplified deployment of the ring. (See Figure 6-15.) Chapter 6 Figure 6-14 Cut in BWDM fiber. Logical Connections BWDM Link 1310-nm Link Figure 6-15 BWDM deployment in SRP rings. OPT/SRP BWDM Link 1310-nm Link In Figure 6-16, BWDM technology is used to enhance PoS point-to-point connections to support SONET/SDH APS protection. Using a single pair of fibers, the bidirectional traffic of the working link can run over the first fiber, enabling the second fiber to act as the protection link. Alternatively, a mesh connection topology can be supported between the four routers using the two fiber pairs. BWDM technology is also usable for deploying SRP rings in the metro- politan area. In Figure 6-17, all the routers are part of the same SRP ring. By employing BWDM technology, each of the two systems may be connected Coarse Wavelength Division Multiplexing (CWDM) Technology Figure 6-16 BWDM deployment in PoS mesh. BWDM Link 1310-nm Link Figure 6-17 BWDM deployment in MAN. BWDM Link 1310-nm Link via a single optical fiber and still maintain all SRP ring functionality. Such deployment also provides an enhanced resiliency capability (E-IPS), which is very important when deploying such an SRP ring in the metropolitan area, SO that the failure of an individual node will not affect the traffic between the other routers on the ring. Chapter 6 To wrap up the cha