Confronti remoti di frequenze campione tramite link in fibra ottica.

We describe LinkO, an experimental set up at the Italian National Metrology (INRiM), Torino, in cooperation with the Politecnico di Torino with the aim to perform the frequency dissemination on optical fibers of ultrastable frequency signals at a European scale. this system allows the frequency comparisons of optical clocks at the relative level of some parts in 10^15 with a 1s integration time, overcoming the capabilities of the satellite based techniques. Up to now the relative stability of the optical link is at the level of 2x10^-15 on a protorype system based on 50km fiber spools inside the lab.