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Time Synchronization over a Free-Space Optical Communication Channel



Isaac H. Khader, Laura C. Sinclair, William C. Swann, Hugo Bergeron, Nathan R. Newbury, Jean-Daniel Deschenes


Free space optical (FSO) communication channels are typically used to transmit high-speed data between sites over the air. Here we repurpose an FSO digital communication system and use it directly for two-way time transfer. We demonstrate real-time synchronization between two sites over a turbulent air path of 4 km using binary phase modulated CW laser light. Under synchronization, the two sites exhibit a fractional frequency deviation below 10u^-15 and a time deviation below 1 picosecond at one-hour averaging time. Over an 8-hour period the peak to peak wander is 16 ps.


Optical communications, Metrology
Created December 20, 2018, Updated September 4, 2019