Abstract: An optical fibre waveguide comprising a glass or vitreous silica fibre is coated with a synthetic resin material, preferably a thermosetting resin such as a polyurethane resin, containing in at least part of its thickness a dispersion of a powdered non-metallic inorganic filler such as lampblack, silica flour or titania powder. The filler material has a modulus of elasticity at least as high as that of the glass or silica fibre, and its presence in the coating composition increases the elastic modulus of the latter, thus improving the load carrying capacity of the coated fibre, to an extent depending on the thickness of the coating. The coating preferably consists of a plurality of thin layers, which may be of varying composition in respect of the filler materials incorporated and the proportions of filler used. A repetitive recycling process for forming a plurality of coating layers on the fibre is described.