Application of ultra-stable laser in coherent optical frequency transfer

We demonstrate the effect of utralstable laser in the high-precision coherent phase transfer of optical frequency. The ultra-stable laser with a linewidth of 0.68 Hz is applied for the optical frequency transfer over a 100 km-fiber link, achieving a transfer instability of 4.9× 10-17 at 100 s, which is about one order of magnitude superior than that with a 2.7 kHz linewidth laser, two times less than that with a 50 Hz linewidth laser. This indicates that the ultrastable lasers will play an important role in the optical frequency transfer.