Femtosecond atmospheric frequency transfer based on joint phase locking and compensation of optical frequency comb

We have demonstrated an atmospheric frequency transfer based on joint phase locking and compensation of optical frequency comb (OFC). With this transfer scheme, a highly stable 4 GHz radio frequency (RF) signal was disseminated over a 100-m long free-space link for 5000 s, and the characteristic of timing fluctuation and instability for the transfer was measured and discussed. The experimental results show that the total root-mean-square (RMS) timing drift of the transferred RF signal with compensation is about 208 fs with a fractional frequency instability on the order of 3.8 × 10 −13 at 1 s and 3.8 × 10 −16 at 1000 s.