Calibration of Fiber-Optic Time Synchronization System Over 800km

SummaryDue to the excellent performance in accuracy and stability, fiber-optic time synchronization is becoming a key technology in the field of time-frequency metrology. And the accuracy of fiber-optic time synchronization system mainly depends on asymmetry calibration. Here we study the calibration of time synchronization system over 800km laboratory fiber link. Asymmetry caused by chromatic dispersion, bidirectional EDFAs, sending and receiving devices are investigated. After calibration, the residual of clock difference between two sites is 56.80ps, and the timing jitter is 33.91ps. By further optimizing the whole system and the method of calibration, a system with accuracy better than 50ps over thousands of kilometers fiber link is expected to be obtained in the future.