Method for calibrating a light source of a medical device, wherein the light source can be connected to at least one light-conducting fibre in such a way that electromagnetic radiation of a defined light output, which is generated by the light source, is at least partially coupled into the light-conducting fibre, wherein the medical device is connected to at least one calibration port, the calibration port including sensor means for determining a spatial radiation pattern of a light-conducting fibre introduced into the calibration port, the method comprising the following steps: a) connecting the light-conducting fibre to the light source, b) inserting a positioning device for the light-conducting fibre into the calibration port, the positioning device having a receiving channel for receiving the light-conducting fibre and at least one radiation aperture, the at least one radiation aperture enabling the transmission of a light output coupled out of the light-conducting fibre in at least one defined spatial direction, c) inserting the light-conducting fibre into the receiving channel of the positioning device, d) coupling electromagnetic radiation of a defined light output into the light-conducting fibre, e) determining the spatial radiation pattern of the light output coupled out of the light-conducting fibre in the region of the calibration port as an actual radiation pattern, f) determining a desired radiation pattern of the light output coupled out of the light-conducting fibre in the region of the calibration port for the light output coupled into the light-conducting fibre by means of the sensor means, g) comparing the determined actual radiation pattern with the determined desired radiation pattern, h) releasing, if the actual radiation pattern corresponds to the desired radiation pattern, the light-conducting fibre for further use, and i) outputting an error message if the actual radiation pattern does not correspond to the desired radiation pattern, characterized in that the sensor means comprise at least one lateral photodiode located laterally on the calibration port and at least one frontal photodiode located at a longitudinal end of the calibration port, wherein determining the actual radiation pattern comprises determining the respective photocurrent generated in the photodiodes by the light output coupled out from said light-conducting fibre, and wherein comparing the determined actual radiation pattern with the determined desired radiation pattern comprises comparing the determined photocurrents with photocurrents included in the desired radiation pattern for the respective photodiodes. a) connecting the light-conducting fibre to the light source, b) inserting a positioning device for the light-conducting fibre into the calibration port, the positioning device having a receiving channel for receiving the light-conducting fibre and at least one radiation aperture, the at least one radiation aperture enabling the transmission of a light output coupled out of the light-conducting fibre in at least one defined spatial direction, c) inserting the light-conducting fibre into the receiving channel of the positioning device, d) coupling electromagnetic radiation of a defined light output into the light-conducting fibre, e) determining the spatial radiation pattern of the light output coupled out of the light-conducting fibre in the region of the calibration port as an actual radiation pattern, f) determining a desired radiation pattern of the light output coupled out of the light-conducting fibre in the region of the calibration port for the light output coupled into the light-conducting fibre by means of the sensor means, g) comparing the determined actual radiation pattern with the determined desired radiation pattern, h) releasing, if the actual radiation pattern corresponds to the desired radiation pattern, the light-conducting fibre for further use, and i) outputting an error message if the actual radiation pattern does not correspond to the desired radiation pattern, the sensor means comprise at least one lateral photodiode located laterally on the calibration port and at least one frontal photodiode located at a longitudinal end of the calibration port, wherein determining the actual radiation pattern comprises determining the respective photocurrent generated in the photodiodes by the light output coupled out from said light-conducting fibre, and wherein comparing the determined actual radiation pattern with the determined desired radiation pattern comprises comparing the determined photocurrents with photocurrents included in the desired radiation pattern for the respective photodiodes.