Time and frequency measurements are vital in many areas of science, industry and trade. Satellite navigation, for instance, is made possible by atomic timekeeping. The forthcoming optical definition of the SI second, spurred by innovations in optical atomic clocks, could, among other benefits, lead to millimetre-precision positioning. Agreement between clocks requires reliable communication of time and frequency signals, but for affordability these signals need to be able to use commercial fibre networks.
The previous NEAT-FT and OFTEN projects culminated in the first international optical clock comparison at the level of uncertainty of the clocks themselves. On the way to a universal tool, this project will refine techniques for transferring data over shared fibreoptic networks, by improving phase coherence and automated link management. Novel applications will be investigated, with geodesy (the Earth’s shape, position and gravitational field) used as an example application. International time scales, synchronised over shared fibre networks, are expected to lead to novel time-keeping concepts with order-of-magnitude improvements in accuracy.