Free-space-based multiple-access frequency dissemination with optical frequency comb

We demonstrate a free-space-based multiple-access frequency dissemination with an optical frequency comb by using a passive phase conjunction correction technique. Timing fluctuations and Allan Deviations are both measured to characterize the excess frequency instability incurred during the frequency transfer process. By reproducing a 2 GHz radio-frequency signal at a middle point over a 60-m long free-space link in 5000 s, the total root-mean-square (RMS) timing fluctuation was measured to be about 224 fs with a fractional frequency instability on the order of 8 × 10 -14 at 1 s and 1 × 10 -16 at 1000 s. This free-space-based multiple-access frequency transfer with passive phase conjunction correction can be used to disseminate a stable frequency signal at an arbitrary point in a free-space link.