A novel online rotor condition monitoring system using fiber Bragg grating (FBG) sensors and a rotary optical coupler

Abstract

Online strain measurement of rotating blades has been achieved with fiber Bragg grating (FBG) sensors and a rotary optical coupler constituted by two lenses and an air gap between them. In addition to the FBG sensors installed in blades, a FBG sensor having a minimal effect on the deformation of a blade was introduced and utilized to compensate the inevitable light intensity loss change due to shaft rotation. The rotary optical coupler enables continuous transmission of optical information about local deformation on a blade to a signal processing unit at the stationary side. Strains at five different locations along the blade were successfully measured online, while the rotating speed is changed rapidly.