This dataset contains the data points of all figures on the paper "Quasi-Single-Mode Transmission over Ultra-Low-Loss Few-Mode Fibre for Data Centre Interconnects". A description of the files is presented below:nli_ase_fitting.xlsx, snr_vs_lpower_fitting.xlsx & snr_vs_lpower_fibrea_ullfmf.xlsx: These files contain the signal-to-noise ratio as a function of launch power for the full reproduction of Fig. 2(a).filter_taps.xlsx: Filter weights obtained for the utra-low-loss few-mode fibre at optimum launch power. This file allows full reproduction of Fig. 2(b).mpi_vs_wav.xlsx: This file contains the multipath interference results as a function of the wavelength obtained based on power samples and on the modified Gaussian model. It allows full reproduction of Fig. 3.snr_vs_wav_nodbp.xlsx: This file contains the signal-to-noise ratio analysis as a function of the wavelength for fibre A and the ultra-low-loss few-mode fibre. This file allows full reproduction of Fig. 4.