High-precision time transfer over a local ring fiber link

We propose a low-cost scheme for multi-access time transfer with high-precision over a local ring fiber link. The time signals are delivered to both the clockwise and anticlockwise directions over a single optical fiber by employing the same wavelengths. The proposed scheme is validated in experiment over a fiber-optic loop link with different lengths. The results demonstrate that the time deviation (TDEV) of less than 20 ps/s and 2 ps/10(4) s can be achieved for the fiber link up to 70 km. The evaluated uncertainty is less than 354 ps, which is mainly limited by the employed time interval counters. The maximum number of accommodated nodes is also theoretically evaluated based on the conditions of signal attenuation and backscattering effect.