Comparison of DAS Data Obtained by Controlled Experiments Using Several Interrogators and Fiber Cables

We conducted a controlled experiment for DAS (Distributed Acoustic Sensing) to evaluate the capability of different interrogators and the applicability of different types of fiber cables. Three interrogators and five fiber cables, including strain sensing and telecommunication cables, were employed for the experiment. We compared the DAS data by an active source, ambient noise, and natural earthquakes. The data obtained by the three interrogators are slightly different, but the data quality is good enough. There are no significant differences in the observed data quality between the strain-sensing and telecommunication cables. The cables were buried directly in the ground so that the fiber cable had a good coupling to the ground. This result indicates that the telecommunication cable, which is not designed for sensing, can be used for DAS measurement if the cable has a good coupling to the ground. The obtained good quality DAS data allows us to estimate the S-wave velocity profile by analyzing ambient noise. In addition, the amplitude spectrum of DAS data is consistent with the amplitude of the waveforms calculated by subtracting the two adjacent geophones. This fact implies that DAS data is applicable to earthquake observations.