Among the most powerful techniques for the exploration of the Universe is very long baseline interferometry (VLBI), which is based on the simultaneous observation of radio sources in the sky with arrays of distant ground-based antennas. One of the effects currently limiting its ultimate sensitivity is the phase-instability of the reference clocks adopted at each antenna. This term can be made negligible delivering the same clock signal to multiple telescope sites using optical fibers. We realized such an infrastructure by disseminating a coherent optical frequency signal to two distant radio telescopes using a 1739-km-long fiber. We performed a 24 h geodetic VLBI campaign in which the same clock reference was used at both telescopes and analyzed it using standard VLBI procedures. The results were consistent with the expectations, confirming that the proposed approach is feasible and configures as a novel tool for studying the role of clocks, troposphere, and systematic effects in the ultimate VLBI resolution.

中文翻译：

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使用相干光纤链路的通用时钟超长基线干涉仪

探测宇宙最强大的技术之一是很长的基线干涉测量法（VLBI），它是基于同时观测天空中带有远距离地面天线的无线电源。当前限制其最终灵敏度的影响之一是每个天线采用的参考时钟的相位不稳定性。使用光纤将相同的时钟信号传输到多个望远镜站点可以忽略不计。我们通过使用1739公里长的光纤将相干的光频率信号传播到两个遥远的射电望远镜来实现这样的基础设施。我们进行了24小时的大地测量VLBI活动，其中两个望远镜都使用了相同的时钟参考，并使用标准VLBI程序对其进行了分析。结果符合预期，