A micro-vibration measurement method based on isostrain cantilever and cascade self-demodulated FBG pair

A micro-vibration measurement method is proposed based on isostrain cantilever structure and cascade self-demodulated fiber Bragg grating (FBG) pair. The micro-vibration is measured with a cantilever structure which can induce a differential shift of FBG pair's Bragg wavelengths. The cross-sensitivity to temperature can be eliminated simultaneously. Both having the capability of self-demodulation, the topology of cascade FBG pair structure has an equivalent measure range, a simpler structure, and a better resolution capability than that based on a twice reflection FBG pair structure. With a preliminary experimental setup a high resolution better than 0.0003 mm can be achieved.