A row of optical fibres is  post-processed to make one part of an all-fibre pseudo-slit reformatter. This section is made of a bundle of optical fibres, kept in a row and we label it the 'ribbon' section. The pseudo-slit reformatter devices convert the modes of a multimode core to the modes of a linear pseudo-slit output structure, achieving a diffraction limited pattern in one direction. They are made by sweeping the fibres with a butane-oxygen flame (the saturating light seen in the video) and gently stretching the optical fibres. Read more in our published paper.