A high power fiber laser system has a combiner configured of a plurality of single mode fibers which are fused together so as to define an output end of the fiber combiner. This electrical characteristic quantity is compared with a first predetermined threshold value and a second predetermined threshold value, and a signal signaling an uncertain programming state is produced if the electrical characteristic quantity is between the first predetermined threshold value and the second predetermined threshold value. The sensor is calibrated on a calibration body in at least three rotational positions of a rotating joint of the rotating swivel unit.