The present invention relates to an apparatus for monitoring the process performance of a laser system with a high-power optical fiber cable (3), specifically an optical fiber cable made for transmitting power levels up to and exceeding 20 kW. Generally the fiber cable has an entrance end (1) for an incident beam-light and an exit end (2) where the beam-light is leaving the optical fiber, and wherein at least one of the ends is provided with a connector device (4,5) having sensor means (14) for monitoring the optical fiber cable status. According to the invention the sensor means (14) are located inside the connector device (4,5) and arranged for monitoring and controlling a laser application process during action as well as detection of conditions within the connector device, such as scattered light, temperatures or the like. The sensors (14) are connected to a fiber interlock circuit (30) to activate an interlock break when measured signals are higher than threshold levels(31) and the comparison of the signals to the threshold values is integrated inside the connector device (4, 5). Preferably the sensor means includes diodes (15,16,17) of the light sensor type located in the rear part of the connector device (14,15). A very fast interlock break system is then provided which has the signal control integrated inside the fiber connector.