Raw data used for evaluating the core-dependent MCF propagation loss at 550 nm (Methods)

Fibre cutback method was used to find the core specific loss in the multicore fibre (MCF). Light at 550 nm was imaged onto the facet of one end of 119.5 m of the MCF which was mounted on computer controlled x-y-z translation stages with nm resolution. A sufficiently high numerical aperture lens was used to ensure that only one core was excited at a time. The power of light emerging light was then measured for each core in the MCF by coupling light into each core individually. The process was then repeated for MCF lengths of 89.5m, 10m and 0.97m by keeping the input end of the MCF on the translation stages. The plot of MCF length (m) against insertion loss (dB) is found to be linear for all cores and the loss for each core is given by the gradient of the linear fit.