Real-time free-running time scale with remote clocks on fiber-based frequency network

Abstract

In this paper, we propose a real-time free-running time scale based on four remote hydrogen masers. The clocks in the ensemble were scattered around Beijing, connected by urban fiber links using a novel frequency synchronization system. The remote clock ensemble prevents the time scale from potential problems caused by correlation among co-located clocks. Insofar as it is real-time, it fulfills the requirements for applications such as navigation, telecommunications and so on. The free-running time scale is updated every 1200 s, and a disturbance-resistant algorithm makes it robust to fiber link disturbances and clock malfunctions. The results of a continuous experiment over 224 days are reported. The stability of the time scale outperformed any clock in the ensemble for averaging times of more than approximately 10000 s.

References in corpus (5)

• Sr lattice clock at 1x10^{-16} fractional uncertainty by remote optical evaluation with a Ca clock
• Coherent optical frequency transfer at 5e-19 over a doubled 642 km fiber link
• Coherent optical phase transfer over a 32-km fiber with 1-s instability at $10^{-17}$
• Carrier-phase Two-Way Satellite Frequency Transfer over a Very Long Baseline
• Two-Way Optical Frequency Comparisons Over 100km Telecommunication Network Fibers