Time Reversal Enabled Fiber-Optic Time Synchronization

Over the past few decades, fiber-optic time synchronization (FOTS) has provided fundamental support for the efficient operation of modern society. Due to the finiteness of the speed of light, calculating the fiber link delay is a key step in the traditional FOTS methods to achieve time synchronization. In this article, a time reversal-enabled FOTS method is proposed. Enabled by time reversal, a new idea for FOTS is demonstrated: the clock difference between two sites can be measured without calculating the fiber link delay. Therefore, the data layer is no longer needed to exchange the timing information between two sites. It can also achieve multiple-access time synchronization along the fiber link. Time synchronization performance characterized by time deviation (TDEV) of 25 ps at 1 s and 2 ps at 1000 s on a 230-km fiber link is obtained, and the function of multiple access is demonstrated.