Ultra-Stable Ground Frequency Dissemination via Optical Fibres*

In this report we present a few results on a dissemination system of ultra-stable reference signals at 100 MHz and 1 GHz on a standard fibre network. The signals are simply transferred by amplitude modulation of an optical carrier. Two different approaches for compensating the noise introduced by the link have been implemented. The limits of the two systems are analyzed and several solutions suggested in order to improve the frequency stability and to further extend the distribution distance. Nevertheless, our system is a good tool for the best cold atom fountains comparisons between laboratories, up to 100 km, with a relative frequency resolution of 10-14 (3-5x10-15) at one second integration time and 10-17 (2-3x10-18) for one day of measurement for a 100 MHz reference signal (1 GHz). A further extension of the link using fiber spools and optical amplifiers over 186 km is also reported