Novel fiber-optic torsional vibrometers

Two configurations for a fiber‐optic torsional vibrometer are described, which can be classified as (i) differential and (ii) reference. Common features of both techniques are noncontact measurement, immunity to nontorsional vibration, large dynamic range coupled with passive, miniature, remote sensor heads. Measurements of rotation speed and torsional jitter were made with a total illuminating laser power of 130 μW (reference mode) and 1.5 mW (differential mode). Rotation speeds in the range of 270–19 000 RPM were measured.