Two-Branch Fiber Link for International Clock Networks

We present our work on realizing two-branch fiber links enabling multiple-partner clock comparisons in Europe. We report in detail on the setup connecting two long-haul links and report for the relative frequency stability and accuracy. We report on a combined uptime of 90% for our dual-branch link during almost 1 month. We finally discuss the combined uncertainty contribution of the ensemble of the link architecture to a clock comparison. We show that the frequency transfer uncertainty is 2 × 10
^-19
.