Abstract: Fabrication of microstructured fibres using stacking of a multitude of capillary tubes or using extrusion-based methods may be disadvantageous for a number of reasons, including low longitudinal uniformity, poor cleanness, low reproducibility, high polarization mode dispersion, limited flexibility of fibre design etc. The present inventors have, however, realized that the use of extrusion or a multitude of capillary tubes for the fabrication of micro-structured fibres with periodic cladding structure(s) is not required. The present invention provides new methods for fabrication of the preforms and more simple means for realising preform of high cleanliness. The present inventors have further realised manners of reducing splicing losses between microstructured fibres and conventional fibres, as well as splicing losses between two microstructured fibres.