标题： 全光链路用于远距离光学钟的直接比较 显示英文标题

标题： All-optical link for direct comparison of distant optical clocks

摘要： 我们开发了一个全光链路系统，用于对两个远距离的超稳定光学钟进行远程比较。 基于光纤干涉仪的光载波传输系统被用来补偿通过光纤链路传播过程中积累的相位噪声。 在90公里的链路中，实现了1秒时的$2\times10^{-15}$和1000秒时的$4\times10^{-18}$的传输稳定性。 另外引入了一个主动偏振控制系统，以保持传输光在适当的偏振状态，从而实现了稳定可靠的比较。 全光链路系统的不稳定性，包括那些不受相位噪声补偿影响的掺铒光纤放大器（EDFAs）的不稳定性，在1秒时低于$2\times10^{-15}$，在1000秒时低于$7\times10^{-17}$。 该系统可通过60公里的城市光纤链路直接比较两个远距离的$^{87}$钇铝石榴石晶格钟。 这项技术对于测量光学频率标准的可重复性将是必不可少的。 显示英文摘要

摘要： We developed an all-optical link system for making remote comparisons of two distant ultra-stable optical clocks. An optical carrier transfer system based on a fiber interferometer was employed to compensate the phase noise accumulated during the propagation through a fiber link. Transfer stabilities of $2\times10^{-15}$ at 1 second and $4\times10^{-18}$ at 1000 seconds were achieved in a 90-km link. An active polarization control system was additionally introduced to maintain the transmitted light in an adequate polarization, and consequently, a stable and reliable comparison was accomplished. The instabilities of the all-optical link system, including those of the erbium doped fiber amplifiers (EDFAs) which are free from phase-noise compensation, were below $2\times10^{-15}$ at 1 second and $7\times10^{-17}$ at 1000 seconds. The system was available for the direct comparison of two distant $^{87}$Sr lattice clocks via an urban fiber link of 60 km. This technique will be essential for the measuring the reproducibility of optical frequency standards.