The invention relates to an arrangement in connection with further processing of fibers, ribbons or filaments, the arrangements comprising a coating unit (1) for spreading a coating on fiber, ribbon or filament (2) being processed, a UV illuminator (3) positioned after the coating unit (1) for curing the coating material on the fiber, ribbon or filament (2), and means (6) for applying inert gas to the quartz tube (5) of the UV illuminator (3) whereby the fiber, ribbon or filament (2) being processed is arranged to pass through the coating unit and the UV illuminator quartz tube (5). To provide a sealed structure, an openable protective housing (9) is arranged between the coating unit (1) and the UV illuminator (3), said housing being arranged to constitute a passage sealed from the environment for the fiber, ribbon or filament (2) being processed.