The invention relates to a method for calibrating a light source (104) of a medical device (102). The light source (104) can be connected to at least one light-guiding fiber (112) such that electromagnetic radiation generated by the light source (104) with a defined light output is at least partly coupled into the light-guiding fiber (112). The medical device (102) is connected to at least one calibration port (108), said calibration port (108) having sensor means for ascertaining a spatial emission characteristic of a light-guiding fiber (112) introduced into the calibration port (108). The method has the steps of connecting the light-guiding fiber (112) to the light source (104)； inserting a positioning device (110) for the light-guiding fiber (112) into the calibration port (108), wherein the positioning device (110) has a receiving channel for receiving the light-guiding fiber (112) and at least one emission opening, and the at least one emission opening allows the transmission of a light output coupled out of the light-guiding fiber (112) in at least one defined spatial direction； introducing the light-guiding fiber (112) into the receiving channel of the positioning device (110)； coupling electromagnetic radiation of a defined light output into the light-guiding fiber (112)； ascertaining the spatial emission characteristic of the light output coupled out of the light-guiding fiber (112) in the region of the calibration port (108) as the actual emission characteristic； ascertaining a target emission characteristic of the light output coupled out of the light-guiding fiber (112) in the region of the calibration port (108) for the light output coupled into the light-guiding fiber (112) by means of the sensor means； and comparing the ascertained actual emission characteristic with the ascertained target emission characteristic. The method additionally has the step of releasing the light-guiding fiber (112) for further use if the actual emission characteristic corr
