Abstract: A method of terminating a polymer optical fibre (10) having a longitudinally extending light guiding cor region (11) and longitudinally extending channel-like light confining holes (13). The method comprises restricting a cross-sectional area of the some or all of the holes over a portion of their length adjacent and extending to a terminal end (14) of the optical fibre (10). The cross-sectional area of the holes is restricted, using the inherent properties of the polymeric material, in a manner effectively to increase the cross-sectional area of the light guiding region (11) of the optical fibre (10) adjacent its terminal end (14). Further, a method of splicing two of such polymer optical fibres (10) comprising terminating each of the optical fibres by the above-defined method, aligning them and conjoining their terminal ends (14).