Time stability of a conventional optical link

Time stability of a single-mode 1300 nm fiber-optic link used by two remote time/frequency centers to compare their atomic clocks is discussed. The optical cable is laid in an urban cable duct and passes through two telephone exchanges. The basic measurement has been made on a 2/spl times/10 km loop with one optical transmitter/receiver pair involved. In the RF transfer regime the time stability of the link has the time-deviation flicker-phase floor of about 3 ps. The corresponding frequency stability is good enough to permit practically undistorted transfer of the 5 MHz frequency from a typical 5071A high-performance cesium clock at averaging intervals as low as a few seconds.