This book is the result of the work of an interdisciplinary group of European researchers who have attempted to create a new fibre communication network concept by exploiting the potential benefits of the optical coherent transmission for local area networks (LANs). The project targeted the development of the necessary building blocks to show the performance and the flexibility built into the proposed concept of a multi-channel ultra-wideband network. The system concept developed within the project associates optical frequency division multiplexing with a suitable network architecture and management techniques to allow very high flexibility and efficiency in handling simultaneous transmission over the network (on each optical frequency) of multiple virtual channels, each operating with information rates ranging from a fraction of a Mb up to more than 160 Mb/s. Specialised applications requiring more than the capacity provided by a single optical channel were to be dealt with by parallel transmission over more than one channel. Another important objective of the system was to make the network open to any future evolution by self-reconfiguration without hardware changes.