Two-Branch Fiber Links for International Clock Networks

Comparisons of clocks through fiber links at the continental scale have become a reality in Europe, opening the way to the realization of a clock network. We will show that we can improve the reliability of the frequency comparison by combining several dissemination techniques. We will report on the implemention of a two-branch fiber link, as part of a wider concatenation of links between NMIs in Europe. This is a key step towards a new definition of the SI second based on optical frequency standards and opens novel opportunities for stringent tests of fundamental physics.