I -- Novel Transponder Interfaces: Novel Modulation Formats -- Electronic Channel Equalization Techniques -- Optical Signal Processing Techniques for Signal Regeneration and Digital Logic -- Evolution of Optical Access Networks -- Novel Switch Architectures -- II -- Cross-Layer Optimization Issues for Realizing Transparent Mesh Optical Networks -- Performance Issues in Optical Burst/Packet Switching -- Multi-layer Traffic Engineering (MTE) in Grooming Enabled ASON/GMPLS Networks -- Network Resilience in Future Optical Networks -- Optical Storage Area Networks -- III -- Software Tools and Methods for Modelling Physical Layer Issues -- Software Tools and Methods for Research and Education in Optical Networks.

The explosive growth of data, particularly internet traffic, has led to a dramatic increase in demand for transmission bandwidth imposing an immediate requirement for broadband networks. The primary objective of the COST 291 Action "Towards Digital Optical Networks" was to focus on novel network concepts, subsystems and architectures to enable future telecommunication networks, exploiting the features and properties of photonic technologies. Three working groups were established to deal with these research objectives: WG1 "Optical processing for digital network performance", dealt with the physical layer and implementation related issues of transparent optical networks such as optical signal per bit processing, optical switch architecture designs and implementations as well as transmission related issues. WG2 "Novel network architectures", focused on the evolution of network scenarios including novel network architectures. Also different node architectures and technologies in terms of network performance and functionality were investigated. Three different architectures were studied and compared: circuit (wavelength, waveband, etc.), optical burst and optical packet switched networks. WG3 "Unified control plane, network resilience and service security", dealt as well with the impact of transparency on photonic network architectures and the associated control and protocol issues as on network survivability and security issues, covering topics such as protection and restoration, its impact on routing and wavelength assignment algorithms, fault isolation, disaster recovery, etc. The results obtained within these working groups are collected in this volume.