Optical Frequency fiber dissemination at 10-19 uncertainty level in Italy

We describe the realization of a coherent optical fiber link for the metrological frequency dissemination on the national scale. This infrastructure will improve the frequency references used in radio-astronomy and in atomic physics and will benefit several laboratories in Italy involved in high resolution spectroscopy, matter physics and radioastronomy. The present infrastructure will be part of a forthcoming European network of optical links. This paper describes the haul implementation, the characterization and the future applications of this backbone.