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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 combs7,8,9, stabilized optical-fibre links4,10 and cavity-stabilized lasers4,5,6. 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 combs11,12.

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Figure 1: Schematic of the coherent, frequency-diverse fibre network.
Figure 2: The heterodyne signal between the two independently generated 1,535 nm signals around the network.
Figure 3: Fractional frequency uncertainty (total Allan deviation) of the 1,535 nm beat signal versus averaging time τ for a common 1,126 nm source.


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We acknowledge assistance from J. Stalnaker and T. Fortier with the Ti:sapphire frequency comb and useful discussions with L. Hollberg and T. Rosenband. We acknowledge funding from the National Institute of Standards and Technology and from the DARPA PHOR-FRONT program.

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Authors and Affiliations



I.C. and W.C.S. were responsible for the c.w.-fibre-laser stabilization and associated fibre link, L.L. and J.C.B. for the stabilized 1,126 nm source and associated fibre links, Y.LeC. and C.W.O. for the stabilized 657 nm source and associated fibre link. S.A.D. and Q.Q. for Ti:sapphire frequency comb, W.C.S. and N.R.N. for the fibre frequency comb, and K.S.F., J.W.N. and P.S.W. for the nonlinear fibre and fibre grating used with the fibre comb. I.C. and N.R.N. analysed the data. S.A.D. and N.R.N. designed the experiment.

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Correspondence to Y. Le Coq or N. R. Newbury.

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The authors declare no competing financial interests.

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Coddington, I., Swann, W., Lorini, L. et al. Coherent optical link over hundreds of metres and hundreds of terahertz with subfemtosecond timing jitter. Nature Photon 1, 283–287 (2007).

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