Abstract: An optical conduit (53) for transmitting and releasing luminescent radiation (61, 62, 63) emitted from a luminescent concentrator (51), the luminescent concentrator (51) and optical conduit (52) comprising an optical system which is adapted to release to an area to be illuminated the luminescent radiation which is otherwise trapped in the optical system by total internal reflection. The optical conduit (53) includes a luminaire (57), such as a plurality of scattering regions for scattering trapped light so that the scattered light acquires the angle of incidence required to released from the conduit (53). The scattering regions may be provided by shape irregularities on the surface of the conduit (53) or inhomogeneities within the conduit (53). The conduit (53) may consist of flexible overlaid light guides (65a, 65b and 65c) and a luminaire fitting (55) optically coupled thereto.