stray light and cladding mode light the rough surface can be created in a variety of ways including for example sanding with a fine sand paper sandblasting chemical etching and laser treatment a first photodetector 36 facing the bare fiber portion 10 i detects the intensity of the light scattered off the bare fiber portion a second photodetector 37 facing the input fiber end detects the intensity of back reflected cladding mode light the output signals of the photodetectors 36 37 are provided to a control unit 38 which can control a laser control device 39 to disable or remove the laser beam 31 from the system the laser control device 39 can be a laser shutter or the like in an exemplary embodiment when the magnitude of one or more of the signals from the photodetectors 36 37 exceeds a predetermined threshold the control unit triggers the laser control device 39 to disable the laser beam 31 a second set of photodetectors 46 47 and a further control unit 48 can optionally be provided for the fiber output port similarly to the input port an portion 10 o of the fiber 10 proximate to the output port is bare with a rough surface and is held by a second glass ferule 43 photodetector 46 which faces the bare fiber portion 10 o detects the intensity of the back reflected light scattered off the bare fiber portion photodetector 47 which faces the output fiber end detects the intensity of the forward propagating cladding mode light the further controller 48 can control a further laser control device 49 e g a laser shutter or the like to disable or remove the laser beam from the system or it can control the laser control device 39 in conjunction with the controller.