Ultra-stable optical frequency transfer over an optical telecommunications network with live data traffic

We present here a new approach consisting in using part of an optical telecommunications network carrying simultaneously data traffic. Our 108 km comprises 86 km of dedicated fibre and 22 km of fibre from the French national telecommunications network for technology, education and research (RENATER). The link is a loop with both ends located in Observatoire de Paris to characterize the link stability. The metrological reference frequency signal is provided by a sub-Hz cavity stabilized laser. It is transferred on ITU channel #44 while live Internet data are transferred between University Paris 13 and Aubervilliers RENATER node on ITU #34 with 10 Gbit/s technology. The interconnection between the dedicated fibres and the optical network is realized by using optical add-drop multiplexers (OADM). This allows bidirectional propagation of the metrological signal on the same fibre which is required to compensate the link-induced phase noise using the round trip system.