WDM-Based Fiber-Optic Time Synchronization Without Requiring Link Calibration

In this paper, we propose a fiber-optic time synchronization technique based on the bidirectional wavelength division multiplexing (WDM) transmission over a fiber link. The effect of fiber dispersion on the uncertainty of the system is effectively suppressed by properly allocating the forward and backward wavelength maps. Thus, only an initial easy-to-implement calibration in a back-to-back configuration instead of multiple complicated link calibrations is required. To compensate the propagation delay fluctuations, a large-dynamic-range time pre-compensator with high precision is implemented at the local site, enabling a time signal at the remote site is accurately synchronized with the clock at the local site. Our experiments demonstrate that stabilities in terms of time deviation (TDEV) of less than 29.8 ps at 1s and 5.2 ps at 10
⁴
s and the clock difference of less than 28 ps can be achieved for the fiber link up to 200 km.