Progress of ultra-stable frequency dissemination and synchronization in free space

We demonstrate a new ultra-stable frequency dissemination scheme on L band over 100m atmosphere. By compensating phase noise actively and a series of frequency conversions, the phase fluctuation is well compensated. Two links disseminate different frequency signals phase locked to a common reference simultaneously, and recover the disseminated frequency respectively at remote site. The stability of dissemination with phase compensation in free space is 3×10^-13/s and 4×10^-17/day. The relationship between dissemination stability and propagating distance is also discussed.