Ring interferometer reflection and polarisation rotation suppression - using short source coherence time and input-output polarisers

摘要

A ring interferometer using the Sagnac effect for absolute measurement of rotations or rotation speeds has simple provision for the suppression of the unwanted effects of reflections and polarisation rotation. The ring interferometer light source coherence time is selected as being smaller than the transition time of the light around the light path (L). In particular, the coherence time of the light source may be selected to be smaller than the difference in transition times of both natural wavelengths of the light path. The light from the source (Q) passes through a polariser (POL1) before being coupled into the light path. It is then passed through the same or another polariser (POL2) on being coupled out of the light path after its transition.