This data set is used to conduct research as presented in the manuscript entitled "Near-surface characterization using shear-wave resonances: A case study from offshore Svalbard, Norway" written by Taweesintananon et al. in 2024, which is submitted for peer reviews and publications in a journal. It contains processed strain data in nanostrain unit measured by OptoDAS interrogator through the dark fibers in two submarine telecommunication cables, which were installed into soft sediments at 0–2 m below the seafloor, between Longyearbyen and Ny-Ålesund in Svalbard, Norway. In total, four OptoDAS interrogators are used for DAS data recording: the ends of the inner (L2) and outer (L3) cables in Longyearbyen, and the other ends of the inner (N2) and outer (N3) cables in Ny-Ålesund. The raw data were acquired in August, 2022, and converted to strain data in nanostrain unit. To reduce file sizes, we resampled the DAS strain data from 1.6 to 20 ms time sampling intervals with an antialiasing filter at 80% of the output Nyquist frequency of 25 Hz. After that, we attenuated interrogator noise that occurs in every DAS recording channel. First, we obtained the single-trace interrogator noise model by stacking (a mean calculation) all the DAS data traces in the first 40 km of the cable, in which the instrument noise level was low. Then, we subtracted every trace of the DAS data by the interrogator noise model. The resampled data after the interrogator noise removal have been archived and used in our spectral analysis. The processed data and the power spectra are stored as structured arrays in the MATLAB file format. This data set has no exact positioning data of the fiber optic cable, because they are proprietary to Sikt. However, the distance of each recording channel along the cable from the shore is given in this data set.