Enhanced Phase Noise Reduction in Localized Two-Way Optical Frequency Comparison

High-stability optical frequency comparison over fiber link enables the establishment of ultrastable optical clock networks, having the potential to promote a series of applications, including metrology, geodesy, and astronomy. In this article, we theoretically analyze and experimentally demonstrate a time-delayed local two-way (TD-LTW) optical frequency comparison scheme with improved comparison stability, showing that the fractional instability of optical frequency comparison over a 50-km transfer link can be reduced from 1.30 x 10(-15) to 5.25 x 10(-16) at the 1 s integration time with an improvement factor of 2.48. Additionally, we also for the first time model and experimentally verify the effect of the inhomogeneous phase noise along the fiber link on the system performance. We believe that the theory and technique proposed here will be helpful in developing the high-stability optical clock networks over large-area fiber links.

Automated summary

This article presents a time-delayed local two-way optical frequency comparison scheme with improved stability and verifies its performance through theoretical analysis and experiments. The results show that the fractional instability of the optical frequency comparison over a 50-km fiber link can be significantly reduced. Furthermore, the effect of inhomogeneous phase noise along the fiber link is also modeled and experimentally verified for the first time.