NIST has developed an optical time distributor that uses frequency combs to synchronize clocks across free space links, including open air paths and satellite-to-satellite connections. This method allows for femtosecond-level timing synchronization, significantly improving upon current rf/microwave techniques that are limited to picosecond-level precision.
The optical time distributor consists of a master clock and a remote clock connected via a free space optical link. By exchanging pulses from two frequency combs, the system can synchronize clocks even between moving platforms, such as airborne or satellite clocks. This technique also enables the generation of coherent microwave signals at remote sites, with potential applications in future coherent radar systems.
The method offers a significant improvement over current free-space time/frequency distribution techniques, which are limited to nanosecond to picosecond-level precision after minutes to hours of averaging. NIST’s optical approach can achieve femtosecond-level precision after less than a second of averaging, requiring only a single mode optical link for implementation.
Keywords: frequency combs, femtosecond, free-space
