Microstructured Optical Fibres and Methods Relating Thereto

A method of processing a microstructure fibre comprises (10) providing a microstructured fibre (10) comprising a solid matrix material defining a plurality of elongate holes 30 that extend along a first length of the fibre (10). A uniform pressure is applied to a first end-face of the fibre (10); and a second length of the fibre (10) that at least partially overlaps with the first length is heated. The fibre (10) is arranged such that one or more of the holes (30) experience an effective pressure that is different from the effective pressure experienced by the other holes (30), so that in the second length the one or more holes expand or contract relative to the other holes, and at least one hole expands relative to the whole fibre.