Book excerpt: This volume reveals the latest research on commercial systems with up to 160 OC-48 channels, optical ATM switch architectures, optical multiprotocol lambda and label switching, synchronous optical networks and digital hierarchy, and the Internet Protocol layer. The text includes recent developments in the routing efficiency of multihop optical networks supported by wavelength division multiplexing (WDM) with limited wavelength conversion. It also explores different routing techniques in WDM networks for virtual topology mapping, wavelength routing and assignment, dynamic routing, QoS provisions, and multicasting. The book examines challenges facing carriers and service providers in expanding optical networking capabilities for the next generation Internet.