A system for injecting light, includes an optical coupler having: a lens having a convex entrance face of radial extent R1, a convex central exit face and a peripheral exit face; a cavity, containing the entrance face and with an entrance lateral surface; and a peripheral reflective surface, encircling the lens and the cavity, extending beyond the entrance face; an optical collector, with an entrance, a collecting surface facing the central exit face, and a numerical aperture NA smaller than 1, the collector including a jacket having an end surface; and a member for aligning the optical collector, the optical coupler and the aligning member being integrally formed or being indirectly or directly fastened together, the central distance eF on the axis Oz between the collecting surface and the central exit face being nonzero and smaller than 5 mm, and the system including a stop for the end surface.