High-Precision Synchronization Using Laser-Based Free Space Time Transfer

The high-precision time synchronization is very important to the fundamental scientific research and engineering application. A scheme of synchronization with laser-based free-space time transfer is presented. A time signal produced by a continuous wave (CW) laser is transferred over a 120 m free-space link. An hundred picosecond-level time synchronization between transmitter and receiver is realized with a time delay correction technique. A synchronization experiment shows an absolute time delay of 480 ns is improved to be 300 ps with an active time delay correction. The time stability is below 40 ps at 1 s and below 20 ps over 10 s, respectively. This experimental results prove that this scheme is effective for high-precision time transfer and synchronization over free-space link.