Coherent Interferometry over Telecom Networks for Time-Frequency Distribution and Geophysical Sensing

In the last decade, fiber networks for telecommunication have started to be exploited in a metrological context, for the distribution of accurate time-frequency signal to both research institutes and commercial partners. Time and frequency distribution over fiber is nowadays enabling most of high-resolution comparisons of atomic clocks between distant Metrological Institutes all over Europe and has been adopted in other fields both in fundamental and applied science. Recently, we demonstrated that the same technique can be used to detect weak earthquakes and other acoustic phenomena. This raised strong interest in the geophysical community, especially in view of its exploitation in seas and oceans, where currently no sensors are available. Our contribution describes the basics of technique and achieved results, with particular attention to geophysical applications, and future perspectives.