Istituto Nazionale di Ricerca Metrologica, INRIM, Strada delle Cacce 91, 10135 Torino, Italy.
Istituto Nazionale di Astrofisica, Istituto di Radioastronomia, Bologna, Italy.
Sci Rep. 2017 Feb 1;7:40992. doi: 10.1038/srep40992.
We describe a VLBI experiment in which, for the first time, the clock reference is delivered from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km long. The experiment consisted of a 24-hours long geodetic campaign, performed by a network of European telescopes; in one of those (Medicina, Italy) the local clock was alternated with a signal generated from an optical comb slaved to a fibre-disseminated optical signal. The quality of the results obtained with this facility and with the local clock is similar: interferometric fringes were detected throughout the whole 24-hours period and it was possible to obtain a solution whose residuals are comparable to those obtained with the local clock. These results encourage further investigation of the ultimate VLBI performances achievable using fibre dissemination at the highest precision of state-of-the-art atomic clocks.
我们描述了一个甚长基线干涉测量（VLBI）实验，这是首次使用长达 550 公里的相干光纤链路，将国家计量研究所的时钟参考传递到射电望远镜。该实验由一个由欧洲望远镜组成的网络进行了 24 小时的测地学活动；在其中一个望远镜（意大利的 Medicina）中，当地的时钟与一个由光纤传播的光信号驱动的光学梳产生的信号交替使用。使用该设施和本地时钟获得的结果质量相似：在整个 24 小时期间都检测到了干涉条纹，并且可以获得一种解，其残差与使用本地时钟获得的解相当。这些结果鼓励进一步研究使用最先进的原子钟的最高精度进行光纤传播所能实现的最终 VLBI 性能。
