title: Simultaneously precise frequency transfer and time synchronization using feed-forward compensation technique via 120 km fiber link.
abstract: Precision time synchronization between two remote sites is desired in many applications such as global positioning satellite systems, long-baseline interferometry, coherent radar detection and fundamental physics constant measurements. The recently developed frequency dissemination technologies based on optical fiber link have improved the transfer instability to the level of 10(-19)/day at remote location. Therefore it is possible to keep clock oscillation at remote locations continuously corrected, or to reproduce a "virtual" clock on the remote location. However the initial alignment and the correction of 1 pps timing signal from time to time are still required, besides the highly stabilized clock frequency transfer between distant locations. Here we demonstrate a time synchronization based on an ultra-stable frequency transfer system via 120-km commercial fiber link by transferring an optical frequency comb. Both the phase noise compensation in frequency dissemination and temporal basis alignment in time synchronization were implemented by a feed-forward digital compensation (FFDC) technique. The fractional frequency instability was measured to be 6.18 × 10(-20) at 2000 s. The timing deviation of time synchronization was measured to be 0.6 ps in 1500 s. This technique also can be applied in multi-node fiber network topology.
authors.affiliation: State Key Laboratory of Advanced Optical Communication System and Networks, School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Advanced Optical Communication System and Networks, School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, China.
authors.forename: Jinlong
authors.initials: J
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Advanced Optical Communication System and Networks, School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, China.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Cui
authors.affiliation: State Key Laboratory of Advanced Optical Communication System and Networks, School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.affiliation: State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Xing
authors.initials: X
authors.lastname: Lu
authors.affiliation: School of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Xusheng
authors.initials: X
authors.lastname: Tian
authors.affiliation: School of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Ci
authors.affiliation: School of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.affiliation: School of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Wu
authors.affiliation: Beijing Satellite Navigation Center, Beijing 100094, China.
authors.forename: Tingsong
authors.initials: T
authors.lastname: Tang
authors.affiliation: State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Kebin
authors.initials: K
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Advanced Optical Communication System and Networks, School of Electronics Engineering and Computer Science, Peking University, Beijing, 100871, China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Zhang