Femtosecond optical-to-microwave frequency divider with a relative instability of $10^{-4}-10^{-16}$ ($\tau=1-100$ s)

We have developed a low-noise optical-to-microwave frequency divider based on a femtosecond erbium fibre laser. The source of an optical signal was a $\mathrm{He}-\mathrm{Ne}/\mathrm{CH}_4$ frequency standard. Comparison of two frequency dividers showed that the relative instability of output microwave signals, introduced by the dividers, is $10^{-4}-10^{-16}$ for the averaging time $\tau=1-100$ s. The instability obtained corresponds to the requirements imposed on interrogative oscillators for time and frequency standards based on Cs or Rb atomic fountains.