Abstract: A generator comprises a lamp (1), an optical unit (2-3) which concentrates the light around an axial image point (5), a ferrule for an optical-fiber bundle, comprising a cylindrical part (7) which, on the one hand, retains the end of the optical-fiber bundle and, on the other hand, surrounds a transparent rod (12) which is brought into contact with the end of the optical-fiber bundle. The end of the transparent rod (12) facing the optical unit and the lamp has a concave surface, the axial image point (5) around which said optical unit concentrates the light is a virtual image point situated inside said rod, and the end of the fiber bundle (6) is polished and brought into contact with the transparent rod (12) by any suitable mechanical means.