High-accuracy optical attenuator continuously variable in the range of 1:20

Abstract
A continuously variable optical attenuator is described that uses optical fiber light guides and high-accuracy dial micrometers mounted on mechanical stages. The attenuation factors thereby obtained have proved reproducible to ∼0.1% over a dynamic range of 1:20. It should, therefore, be particularly useful in testing the linearity of the response of various photodetectors.