An eye-safe optical fiber transmitter unit comprises a laser, an optical port, an optical fiber stub with a fiber core carrying optical radiation emitted by the laser to the optical port. The core is an index-guided core surrounded by cladding. Laser radiation is focussed to a spot on a fiber stub entrance face to increase the coupling efficiency of optical radiation into the fiber core and decrease the radiation coupling efficiency of radiation into the surrounding cladding. The coupling efficiency into the core is a maximum at a particular orientation of the entrance face with respect to a focus axis when the focus spot is on the entrance face. The entrance face is not oriented at this particular orientation, but is angled and/or rotated away from the particular orientation to reduce optical coupling efficiency into the fiber core and cladding.
Eye-safe optical fiber transmitter unit