First industrial-grade coherent fiber link for optical frequency standard dissemination.

Abstract

We report on a fully bidirectional 680km fiber link connecting two cities for which the equipment, the setup, and the characterization are managed for the first time by an industrial consortium. The link uses an active telecommunication fiber network with parallel data traffic and is equipped with three repeater laser stations and four remote double bidirectional erbium-doped fiber amplifiers. We report a short-term stability at 1s integration time of 5.4×10-16 in 0.5Hz bandwidth and a long-term stability of 1.7×10-20 at 65,000s of integration time. The accuracy of the frequency transfer is evaluated as 3×10-20. No shift is observed within the statistical uncertainty. We show a continuous operation over five days with an uptime of 99.93%. This performance is comparable with the state-of-the-art coherent links established by National Metrology Institutes in Europe. It is a first step in the construction of an optical fiber network for metrology in France, which will give access to an ultrahigh performance frequency standard to a wide community of scientific users.