This book describes an investigation of technologies and sub-systems for physical layer implementation of dynamic wavelength-routed optical networks, including optical-burst-switching(OBS) architectures, operating with millisecond burst lengths. The key sub-systems and existing solutions are identified and new systems are developed where appropriate. The initial focus is the tunable transmitter. Available laser technology is identified, the operation of fast tunable lasers investigated, and a burst transmitter using SOA blanking and wavelength locking is developed. Next, the characterization and analysis of the first 10Gb/s digital burst-mode receiver, based on an AC- coupled photodiode, asynchronous digital sampling at 20GS/s and digital signal processing, is described. Subsequently, the optimum performance of optically gain-clamped EDFAs is investigated. Finally, an experimental OBS link model, comprising the burst transmitter, receiver, gain-clamped amplifiers, wavelength routers and fiber spans within a recirculating transmission loop is described. The model is used to investigate sub- system inter-operability and implications for overall network design.