In-line extraction of an ultra-stable frequency signal over an optical fiber link

In the frame of the REFIMEVE+ project, aiming at disseminating an optical frequency standard to more than 20 laboratories in France, we present the progress made towards a metrological fibre wide-area network. We specifically address the key issue of multi-user dissemination and demonstrate in-line extraction on a main link, as first proposed by G. Grosche in 2010 [4].