Electro-optic time transfer with femtosecond stability

Optical two-way time and frequency transfer (O-TWTFT) is an enabling technology that has applications ranging from fundamental investigations of relativity to the operation of global navigation satellite systems. Linear-optical-sampling (LOS) between optical frequency combs has been used to create very stable optical two-way time and frequency transfer links over free-space. Here, we demonstrate two-way time and frequency transfer using LOS between electro-optic frequency combs. This two-way electro-optic time and frequency transfer system demonstrated instabilities as low as 15 fs at 1 s of averaging time. These results show a pathway to highly stable, frequency agile, and low SWaP-C time transfer networks.