Optical technology is already the dominant carrier of global information. It is also central to the realisation of future networks which have the capabilities demanded by society. For example, essentially unlimited bandwidth to convey services of any kind, full transparency that allows terminal-only upgrades in capacity, and flexible routeing of channels are some of the key features that cannot be provided by alternative technologies. In the main, all of the necessary elements for such networks already exist in experimental form, and rapid progress is being made towards a field deployment capability. This will bring about a paradigm change in the whole nature of telecommunications as we move into the third millennium.