An optical waveguide in the form of an optical fibre (10) having at least one longitudinally extending light guiding core region (11) composed at least in part of a polymeric material, a longitudinally extending core-surrounding region (12) composed of a polymeric material, and a plurality of light confining elements (15), such as, for example, channel-like holes, located within the core surrounding region. The light confining elements extend in the longitudinal direction of the core region and are distributed about the core region, and at least a majority of the light confining elements having a refractive index less than that of the polymeric material from which the core-surrounding region is composed. A preform for use in manufacture of the optical waveguide is also disclosed.