A 1800-km optical fiber link for metrology, geodesy, and clock comparison

Nowadays, optical fiber links are key elements in optical metrology, spectroscopy, quantum communication and geodesy. In geodetic Very Long Baseline Interferometry, a local maser is responsible for providing time and frequency reference at radiotelescope. Here, we present our recent results on frequency dissemination using a coherent fiber link 1800 km long from Turin to Medicina and Matera, Italy. Metrological reference disseminated via fiber link improve the stability of about two order with respect to the local H-maser clocks. This kind of dissemination paves the way to VLBI observation using a remote clock reference on the Italian and European radio observatories.