30-km-long optical fiber link at 1397nm for frequency comparison between distant strontium optical lattice clocks

摘要

We demonstrate a 30-km-long optical fiber link for frequency comparison between two strontium optical lattice clocks being developed at RIKEN and the University of Tokyo. We use a transfer laser at 1397 nm, which is twice the wavelength of the clock transition of strontium clocks. The link stability is estimated to be 1 × 10~(-17) for an averaging time of r = 1 s, which is in good agreement with the theoretical limit calculated from the fiber noise spectrum. We discuss a remote clock comparison with a stability of 1 × 10~(-17)(T/S)~(-1/2) by synchronously operating two distant clocks.