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We describe the application of Raman optical-fiber amplification (ROA) for the phase coherent transfer of optical frequencies in an optical fiber link. ROA uses the transmission fiber itself as a gain medium for bi-directional coherent amplification. In a test setup, we evaluated the ROA in terms of ON/OFF gain, signal-to-noise ratio, and phase noise added to the carrier. We transferred a laser frequency in a 200 km optical fiber link, and evaluated both co-propagating and counter-propagating amplification pump schemes. Then, we identified the occurrence of nonlinearities on the signal for non-optimized ROA gain. The frequency at the remote end has a fractional frequency instability of 3·10 -19 over 1000 s with the optical fiber link noise compensation.
Publication date: 
15 Jul 2013

Cecilia Clivati, Gabriele Bolognini, Davide Calonico, Stefano Faralli, Filippo Levi, Alberto Mura, Nicola Poli

Biblio References: 
Volume: 25 Issue: 17 Pages: 1711-1714
IEEE Photonics Technology Letters