Performance Investigation on a Clock Distribution and Synchronization Scheme Over DWDM Optical Links

Abstract

For most large-scale physics experiments, it is desirable that the clock distribution and data transmission are unified on a single optical network. To meet the requirement of current large-scale physics experiments for clock synchronization accuracy in the range of tens of picoseconds, and adapt to the increasingly widespread use of dense wavelength division multiplexing (DWDM) optics, this paper investigates the performance of clock distribution and synchronization scheme based on DWDM optics and high-speed serializer-deserializer (SerDes) transceivers embedded in field programmable gate arrays (FPGAs). By extending our previously proposed simplified calibration procedure based on the White Rabbit protocol to the present asymmetric link, all possible errors, especially the new factors brought about by the asymmetric link, are investigated so that the time uncertainty on the link can be minimized. Using the built test system to carry out multiple Reset and long-term operation tests, the measured clock synchronization accuracy over a 5km optical fiber connection is better than 20ps, and the RMS jitter of the recovered clock is less than 10ps. The test results show that the combination of White Rabbit with DWDM optics can have both high-bandwidth data transmission and high-performance clock synchronization at the same time.