Abstract: A body (2) of UV settable polymer material is quickly cured to a solid state by applying UV radiation from a lamp (4). The polymer is mixed with strands (3) of optical fibres. The radiation is able to penetrate up to 3 mms through the polymer allowing it to enter the optical strands and to pass between adjoining strands so as to penetrate uniformly the whole of the polymer body. The optical strands can be designed so that they leak radiation from their sides thereby assisting in the transfer of radiation from a strand into the polymer and into other strands. In an alternative arrangement the strands can be longer and possibly woven or otherwise formed into a mat of fibres sufficiently close to allow radiation to pass between them. Because the radiation passes from one fibre to another, it can be introduced through only one or a selection of the fibres.