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.