The present invention relates to a method of calibrating a light source (104) of a medical device (102), the light source (104) being connectable to at least one light guiding fiber (112), resulting in a defined light source (104). Electromagnetic radiation of optical power is at least partially coupled into the light guiding fiber (112). The medical device (102) is connected to at least one calibration port (108), the calibration port (108) providing a sensor means for determining the spatial emission characteristic of the light guiding fiber (112) introduced into the calibration port (108). Have. In this case, the method comprises connecting the light guiding fiber (112) to the light source (104) and inserting the positioning device (110) of the light guiding fiber (112) into the calibration port (108), The positioning device (110) also has a receiving channel for receiving the light guiding fiber (112) and at least one radiating opening, the at least one radiating opening providing optical power separated from the light guiding fiber (112). Directing at least one defined spatial direction, introducing a light guiding fiber (112) into a receiving channel of the positioning device (110), and guiding electromagnetic radiation of defined optical power. Coupling into the fiber (112), determining the spatial radiation characteristic of the optical power separated from the light guiding fiber (112) as the actual radiation characteristic in the area of the calibration port (108), and guiding the light guiding fiber (112). ) Separating the desired emission characteristic of the optical power from the sensor means in the area of the calibration port (108) for the optical power coupled to the light guiding fiber (112) and the determined actual emission characteristic. With the determined desired emission characteristic. If the actual radiation characteristic corresponds to the desired radiation characteristic, the method further comprises emitting the light guiding fiber (1
