Precision Time Transfer using ITU-T G.8275.1 over Optical Transport Network

There is a need for transport synchronization reference signal across an optical network for 5G RAN. The traditional optical transport network (OTN) in case of transparent transporting a timestamp signal is not guaranteed to keep its accuracy. This experiment connected a precision time protocol (PTP) grandmaster and a PTP time slave clock via optical transport network without any vendor-specific encapsulation or operation for time transfer. Timing signals using ITU-T G.8275.1 were sent in the two-way operation. We found that the asymmetry of the PTP time transfer over OTN resulted in variant time transfer errors, even there is no other non-synchronization-related data loading in the same optical channel. We have run simulations of various OTN configurations in the laboratory. Thus, we can conclude with some certainty that similar results will be applicable if this technique are used to transfer time and frequency with high accuracy.