Fiber-Optic Frequency and Timing Transfer Over an Urban Optical Fiber Link

Abstract

We have developed a fiber-optic frequency and timing transfer system. It has been installed to provide timing synchronization between NICT and a distant university site connected by a 58-km urban optical fiber link. The timing signal generated at the remote site is derived from a frequency source that is stabilized using the link, and it is synchronized by a transferred timing marker. A second, separate fiber link confirms a timing synchronization uncertainty of 5.7 ns and a 10-MHz frequency instability of less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-16}$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{5}$ </tex-math></inline-formula> s averaging time. We additionally demonstrate a timing marker delivery using a code-based signal, which combines nanosecond-level uncertainty with the simplicity and compactness suitable for a system that can be deployed for synchronization across numerous sites.