Long-distance frequency transfer over an urban fiber link using optical   phase stabilization
  We transferred the frequency of an ultra-stable laser over 86 km of urban fiber. The link is composed of two cascaded 43-km fibers connecting two laboratories, LNE-SYRTE and LPL in Paris area. In an effort to realistically demonstrate a link of 172 km without using spooled fiber extensions, we implemented a recirculation loop to double the length of the urban fiber link. The link is fed with a 1542-nm cavity stabilized fiber laser having a sub-Hz linewidth. The fiber-induced phase noise is measured and cancelled with an all fiber-based interferometer using commercial off the shelf pigtailed telecommunication components. The compensated link shows an Allan deviation of a few 10-16 at one second and a few 10-19 at 10,000 seconds. 
Haifeng Jiang (SYRTE), Fabien K\'ef\'elian (LPL), Scott Crane (SYRTE),   Olivier Lopez (LPL), Michel Lours (SYRTE), Jacques ...