Ice type detection using an oblique end-face fibre-optic technique

Abstract

This paper reports on a novel, compound fibre-optic ice sensor consisting of two source fibre bundles and two signal ones. All the bundles had oblique fibre end-faces that were not perpendicular to the fibre axis. Dynamically icing experiments in an icing wind tunnel showed that with increasing thickness of ice accreted on the sensor, one group, comprising the first source and signal fibre bundles, output decreasing signal for glazed ice, increasing signal for rime ice, and constant signal for mixed ice, while the other group, comprising the second source and signal bundles, output constant signal for rime ice and decreasing signal for glazed or mixed ice. The different ice-growth curves are caused by different optical intensity distributions in the fibres for different ice types and thus can be used to accurately measure the ice type and thickness. This sensor is competitive in ice detection, especially identification of ice type in the aviation industry.