Excess phase noise characterization in multifrequency remote clock distribution based on femtosecond frequency combs

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© 2015 by the authors; licensee MDPI, Basel, Switzerland. Remote distribution of optical frequency references, based on multifrequency sources such as femtosecond frequency combs, holds many advantages over its single-frequency counterpart. However, characterizing the excess noise caused by the transmission links or external perturbations in a multifrequency scheme posts new challenges. We have experimentally demonstrated direct measurement of excess phase noise spectrum in both free-space and fiber-optic transfer of a frequency comb using a multiheterodyne technique. In fiber-optic distribution, we focused on the excess phase noise under a single-tone acoustic perturbation. Increased overall noise power and a change of phase noise spectrum have been observed. In free-space distribution, a fractional instability of 3 × 10-14 at 1 s was observed for a 60 m outdoor atmospheric transmission, and large phase modulation due to air fluctuations causes a sizable line broadening.

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Applied Sciences (Switzerland)

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