The work of Projects on Optical Networks in the Photonic Technologies Area of the European Commission ACTS Programme is described. The projects play a leading role in defining the concepts and developing the technology that will be required for the realisation of pan-European photonic networks. These networks will provide end-to-end optical connectivity, by exploiting the wavelength dimension and using optical-cross-connect nodes, and removing bandwidth limitations in core/transport networks. The progress of the work is demonstrated in field trials which the projects will implement at several locations throughout Europe.