Raw data used to evaluate the relative positions of the MCF cores (Methods)

To measure the spatial arrangements of the cores in the multicore fibre (MCF), one end of the MCF was flood illuminated with white light while mounting the other end of the MCF on a set of nm-precision x-y-z translation (Aerotech) stages. The output is then imaged onto a CCD camera with higher magnification. The core positions were then mapped precisely by moving the translation stages and monitoring the core modes in the camera. In order to quantify how the MCF core positions deviate from a perfect square grid, a computer simulation was then performed.