A laser-radiation source includes a laser delivering an output beam, a
lens, and an optical arrangement for dividing the output beam into a main
beam and an auxiliary beam. The main and auxiliary beams are coupled by
the lens into entrance faces of respectively a main optical fiber and an
auxiliary optical fiber. The entrance face of the main optical fiber is
located on the optical axis of the lens. The entrance face of the
auxiliary optical fiber is laterally displaced from the optical axis of
the lens.