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Micro-vibration or displacement measurement based on a novel Bragg grating pair

Micro-vibration or displacement measurement is very important in modern industrial fields, especially for the micro electrical and mechanical system (MEMS). An optical fiber sensor was proposed to measure the micro-vibration or displacement based on a novel fiber Bragg grating pair, in which one of the gratings is written in the fiber cladding and the other is written in the fiber core, however the positions of the two grating are staggered. Because the reflection spectrum of this structural grating is much sharper than that of ordinary grating, the special reflection spectrum of the fiber Bragg grating pair is used, resulting in a high measurement sensitivity. Theoretical analysis of the fiber Bragg grating pair and micro-vibration or displacement measurement principle with the experimental setup (Micro-vibration is measured by this grating pair, while this grating pair is demodulated by ordinary grating) are introduced in this paper.