Optical networks based on wavelength-division multiplexing (WDM) tech nology offer the promise to satisfy the bandwidth requirements of the Inter net infrastructure, and provide a scalable solution to support the bandwidth needs of future applications in the local and wide areas. In a waveleng- routed network, an optical channel, referred to as a lightpath, is set up between two network nodes for communication. Using WDM technology, an optical fiber link can support multiple non-overlapping wavelength channels, each of which can be operated at the data rate of 10 Gbps or 40 Gbps today. On the other hand, only a fraction of customers are expected to have a need for such a high bandwidth. Due to the large cost of the optical backbone infrastruc ture and enormous WDM channel capacity, connection requests with diverse low-speed bandwidth requirements need to be efficiently groomed onto hi- capacity wavelength channels. This book investigates the optimized design, provisioning, and performance analysis of traffic-groomable WDM networks, and proposes and evaluates new WDM network architectures. Organization of the Book Significant amount of research effort has been devoted to traffic grooming in SONET/WDM ring networks since the current telecom networks are mainly deployed in the form of ring topologies or interconnected rings. As the long-haul backbone networks are evolving to irregular mesh topologies, traffic grooming in optical WDM mesh networks becomes an extremely important and practical research topic for both industry and academia.