Abstract: An apparatus for irradiating the bronchi of a patient for the purpose of photodynamic therapy has an optical fibre (11) that feeds the light of a laser into a bronchoscope and is surrounded by a light-guide tube (8) and an outer tube (2). The distal end (13) of the optical fibre (11) is embedded in a silicone composition (17) containing 7 parts per thousand of TiO.sub.2 particles having a particle size of 0.2 .mu.m. The silicone composition (17) fills the front end of the light-guide tube (8) as far as the end face (6) of an aluminium cylinder (5) which acts as a mirror. The light dispersed by the TiO.sub.2 particles is emitted radially through the light-guide tube (8) and the front portion of the outer tube (2) and acts on the patient's bronchi.

Abstract: An optical waveguide plug connection for the transmission of high continuous wave light powers from an incoming optical waveguide into an outgoing optical waveguide comprises a metallic plug housing equipped with a metallic centering element. The incoming optical waveguide and the outgoing optical waveguide project into the centering element, the end faces of the two optical waveguides being arranged opposite each other. The width of the gap is approximately in the range of from 5 to 30 micrometres. The core diameter of the outgoing optical waveguide is approximately one third larger than the core diameter of the incoming optical waveguide. The gap is filled with gas. The plug housing is connected to a housing of large surface area which dissipates heat. Using this plug connection, continuous wave powers of up to some 100's of watts in the case of visible to infrared laser light can be transmitted with a high degree of coupling without danger to the end faces of the coupling connection.