Development of synthesis chains based on a cryogenic sapphire oscillator

We have developed a 1 GHz synthesis chain based on a cryogenic sapphire oscillator. The 11.2005 GHz output of the CSO is down-converted for laboratory distribution. The frequency stability of the down-converter itself is 2times10^-15 at an averaging time of 1 second. The long-term drift of the CSO is suppressed by referencing it to a hydrogen maser linked to Japan Standard Time. An application of this highly stable reference is absolute frequency measurement of an ultra-narrow clock laser for the optical frequency standard performed using a frequency comb, in which the repetition rate is stabilized by the CSO signal.