Sub-ps resolution clock-offset measurement over a 114 km fiber link using linear optical sampling.

We demonstrate a sub-ps resolution clock-offset measurement based on linear optical sampling technique via a 114 km fiber link by transferring a dual optical frequency comb. The time deviation between two distance clocks is 110 fs at 1 s and 22 fs at 100 s averaging, and the standard deviation of the measured clock offset is 237 fs. This sub-ps level of clock offset measurement should benefit many time synchronization applications via long fiber links.