Cantilever based FBG vibration transducer with sensitization structure

We report a fiber Bragg grating (FBG) vibration transducer based on an equal strength cantilever with enhanced sensitivity design. The sensitivity of the transducer is improved by a buffer layer of polyimide which increases the effective distance between the FBG and the neutral axis of the cantilever. The thickness of the polyimide layer is further optimized by finite element analysis (FEA). Vibration test results demonstrate that the sensitivity is enhanced by about 3.34 times than the conventional design, from the original 10.2 pm/g to 44.3 pm/g, which is consistent with the FEA. It is also shown experimentally that the sensitivity enhancement does not degrade the fundamental vibration characteristics of the cantilever, especially the resonant frequency.