A device for cooling optical components based on optical fibers for transmitting high optical power. The device includes one or more cavities with a flowing coolant to take care of optical power loss. The device includes a transmitting construction material having a low heat expansion coefficient arranged in direct connection with the optical components and arranged to transmit power loss radiation into the cavity which is flushed with the flowing coolant. The transmitting construction material is made as a transparent tube and surrounded by a tubular casing of a non-transparent material having a good absorption capacity so that the cavity is formed between the two materials.
