Distribution of the accurate optical frequency and time via photonic networks in the Czech Republic

To verify the stability of the frequency of optical clock an intensive research in the transmission of stable frequency via optical fibers is in progress for many years. Interconnection of large cities and metropolitan networks with optical fiber running DWDM allowing to transfer many optical signals in parallel over one fiber at the same time contributes significantly to troubleshoot the problem. Between nodes of ISI Brno and the main center of CESNET there are several dedicated bi-directional channels through the DWDM technology. The first tests are ongoing with the transfer of accurate time, which are using the possibility of bi-directional communication over a single fiber, thus the phase delay including Doppler shift are reflected on the two signals as well. From periodic measurements can subsequently be evaluated daily, weekly and seasonal fluctuations of the delay and after deduction of such data from the measured data a mutual stability of used time normal can be determined. The second technique is a full compensation of phase of the laser wave through active control of phase changes of the wave during its transmission from the ISI to the node of CESNET. At present, a characterization of the behavior of individual system elements, including their commissioning is in progress