Fiber-optic strain sensing on rotating shafts

The applicability of fiber-optic sensors to measure strain on rotating shafts is demonstrated by an experimental study. A fiber-optic Fabry-Perot strain gage was placed on a rotating shaft along with a reference resistive (electrical) strain gage to monitor strain. The fiber-optic sensing technique used here is based on white-light interferometry. The shaft was loaded at one end, and the corresponding readings from the two strain gages were recorded simultaneously. The optical and electrical signals were transferred from the rotating part to the stator using optical and electrical slip-rings, respectively. Results indicated a good correlation between the strain data gathered from the two gages. A concept for an off-axis optical slip-ring was also tested with favorable results.