Fiber-laser-based clockwork for long-term measurements and comparisons of visible optical frequency standards

A long-term clockwork capable of linking visible optical frequency standards to the radio frequency domain is demonstrated with a continuous measurement stretching eight days. The clockwork is based on a femtosecond fiber laser frequency comb. Using this system, an uncorrected measurement of the 88Sr+ frequency standard at 445 THz (674 nm) is completed and is in excellent agreement with previous measurements.