The inline fibre-optic attenuator (ATT-INL-EXT) is an iris attenuator designed to control light throughput and prevent detector saturation. It is coupled between two SMA-terminated fibre-optic cables and features two UV/VIS/NIR collimating lenses, one on each side of an adjustable iris. The attenuation can be precisely set from 0% to 100% and securely fixed with a set screw, allowing for fine control over the light intensity.