The present invention relates to a method for calibrating a light source 104 of a medical device 102, wherein the light source 104 is at least partially guided by electromagnetic radiation of a defined optical power generated by the light source 104. It is connectable to at least one light guide fiber 112 to be coupled to the fiber 112. The medical device 102 is connected to at least one calibration port 108, wherein the calibration port 108 is a sensor means for determining the spatial emission characteristics of the light guide fiber 112 encased into the calibration port 108. It includes. In this case, the method comprises: connecting the light guide fiber 112 to the light source 104； Inserting a positioning device 110 for the light guide fiber 112 into the calibration port 108, wherein the positioning device 110 is adapted to receive the light guide fiber 112 and at least one emitting opening. A receiving channel, wherein the at least one emission opening makes it possible to transmit optical power coupled-out from the light guide fiber 112 in at least one defined spatial direction； Inserting the light guide fiber (112) into a receiving channel of the positioning device (110)； Coupling electromagnetic radiation of defined optical power to the light guide fiber (112)； Determining a spatial emission characteristic of optical power coupled-out from the light guide fiber 112 in the region of the calibration port 108 as the actual emission characteristic； Determining a desired emission characteristic of optical power coupled-out from the light guide fiber 112 in the region of the calibration port 108 for the optical power coupled to the light guide fiber 112 by the sensor means； And comparing the determined actual release characteristic with the determined desired release characteristic. The method outputs an error message if the actual emission characteristic corresponds to the desired emission characteristic, releasing the light guide fiber 112 for further use, and
