Abstract: An optical irradiation device is provided which includes a multimode optical fiber suitable for the central wavelength of a beam of light having a first beam profile which enters through an input connection for multimode guidance; a switching device, which can be switched between a first and second light conducting state and is configured to conduct the beam of light entering through the input connection in the first light conducting state to an output connection, such that the beam of light has the first beam profile on emerging from the output connection, and guides the beam of light entering the input connection to the output connection by the multimode optical fiber in the second light conducting state, so that the beam of light has a second beam profile different from the first beam profile on emerging from the output connection by the multimode guidance in the multimode optical fiber.