Coherent optical link over hundreds of metres and hundreds of terahertz with subfemtosecond timing jitter

Recent developments in stabilized lasers have resulted in ultrastable optical oscillators with spectral purities below 1 Hz refs 1-6. These oscillators are not transportable at present and operate at a single frequency. To realize their full potential, a highly coherent, frequency-diverse fibre-optic network is needed to faithfully transfer the optical signals to remote sites and to different optical frequencies. Here we demonstrate such a coherent network composed of erbium fibre and Ti:sapphire laser-based, optical-frequency combs, stabilized optical-fibre links and cavity-stabilized lasers. We coherently transmit an optical carrier over 750 m of optical fibre with conversions to wavelengths of 657, 767, 1,126 and 1,535 nm, an overall timing jitter of 590 attoseconds, and a frequency instability of 12 mHz for the 195 THz carrier in 1 s and 250 µHz in 1,000 s. This first remote synchronization of two frequency combs also demonstrates a factor of 30 improvement in the relative stability of fibre frequency combs.