Portable Picosecond Synchronization Technique Based on Optical Free-Space Time Transfer

A scheme of portable picosecond-level synchronization technique based on optical 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. A picosecond-level synchronization between transmitter and receiver is realized with a time delay correction technique. A synchronization experiment shows an absolute time delay of 480ns is improved to be 300 ps with an active time delay correction. The time stability is below 40 ps at 1s and below 20 ps over 10 s, respectively. This experimental results prove that this portable scheme is effective for high precision time transfer and synchronization over free-space link.