Optical-fiber technologies employing wavelength-division multiplexing (WDM) are currently being researched and commercially deployed to satisfy our increasing bandwidth requirements because, by using WDM technology, an optical fiber can support multiple non-overlapping wavelength channels, each of which typically operates at the data rate of 10 Gbps or 40 Gbps. However, the bandwidth requirements of customer connections are diverse and relatively low, from 50 Mbps (and even lower) to the full bandwidth of a wavelength channel. In order to efficiently utilize the network resources, multiple low-speed connections need to be multiplexed onto a high-capacity wavelength channel, and they need to be intelligently demultiplexed and switched at intermediate nodes before reaching their destinations. This problem is referred to as traffic grooming, which is an extremely important problem for both carriers and vendors. This book will capture the state of the art in the design and analysis of network architectures, protocols, and algorithms to implement efficient traffic grooming in optical WDM mesh networks.