Fiber-optic joint time and frequency transmission with enhanced time precision

Abstract

We propose a high-precision joint time and frequency transmission scheme based on bidirectional wavelength division multiplexing transmission over an optical fiber link. The time signal is generated based on the phase-stable frequency signal with employment of a dedicated designed low-jitter event generator. Time synchronization is realized by eliminating the time difference between the time signals of the master and slave stations, which is determined by accurate two-way time comparison. In this way, thanks to the high stability of the frequency transmission, low jitter of the dedicated designed event generator, and the high accuracy of the two-way time comparison, a high precision time signal with enhanced time stability and accuracy can be obtained at the slave station, which is synchronized to the master station. Experimentally, a joint time and frequency transmission system is demonstrated over a 62-km urban fiber link. The results show a time stability in terms of time deviation (TDEV) of 3.5 ps/s and 430 fs/10,000 s, and an accuracy of better than 20 ps can be realized.