The telecommunications world is evolving dramatically toward challenging scenarios where the fast and efficient transportation of information is becoming a key element in today’s society. Wavelength division multiplexing (WDM) technology has the potential to satisfy the ever-increasing bandwidth needs of the network users on a sustained basis (Mukherjee, 2000). Network operators must provide uninterrupted service to their customers, that is, network survivability must be guaranteed. This means that, networks must be able to handle link or fiber cuts as well as equipment failures, fact that influences the design and operation of networks (Gerstel & Ramaswami, 2000). When using WDM, survivability becomes even more important because of the huge amount of traffic carried by a single fiber. A single fiber failure, even for few seconds, can be catastrophic (Maier, Pattavina, Patre & Martinelli, 2002). This issue is actually very important since the optical WDM technology is now being deployed in the field. Network survivability is not just an academic subject. In real networks, failures happen quite frequently (fiber cuts, for example, are very common in terrestrial networks since they share other utility transport conduits, such as gas or water pipes and electrical cables, and are considered the least reliable component (Gerstel & Ramaswami, 2000; Maier, Pattavina, Patre & Martinelli, 2002). The prevention of service interruption, or the reduction of the service loss when failures occur, must now be an integral part of the network design and operations strategy or otherwise severe service losses can happen.
A Mutual Blocking Technology Applied to Dual Power Source Switching Control