  We demonstrate in-line extraction of an ultra-stable frequency signal over an
optical link of 92-km of installed telecommunication fibers, following the
proposition of G. Grosche in 2010. We show that the residual frequency noise at
the extraction end is noticeably below that at the main link output when the
extraction is near the input end, as expected from a simple model of the noise
compensation. We obtain relative frequency instabilities, expressed as
overlapping Allan deviation, of 8x10-16 at 1 s averaging time and a few 10-19
at 1 day. These results are at the state-of-the-art for a link using urban
telecommunication fibers. We also propose an improved scheme which delivers an
ultra-stable signal of higher power, in order to feed a secondary link. In-line
extraction opens the way to a broad distribution of an ultra-stable frequency
reference, enabling a wide range of applications beyond metrology.
