During the colour coating of optical fibres, it is often necessary to carry out tensile testing at the same time (“screen proof test”), thereby eliminating a separate winding process. In this test the fibre is subjected to a specific tensile force that results in breakage of the fibre in the event of a manufacturing defect. The machine used to carry out this “screen proof test” can easily be incorporated as a separate component in existing colouring equipment. Speed up to 2800 m/min.