Fiber-optic micro vibration sensors fabricated by a femtosecond laser

Fiber-optic micro vibration sensors fabricated by a femtosecond laser are proposed and experimentally demonstrated. The proposed sensor is an extrinsic Fabry-Perot interferometer (EFPI), which is the three-section structure sandwiched by a single mode fiber (SMF), a hollow core fiber (HCF) and a coreless silica fiber (CF). A femtosecond laser is employed to fabricate the cantilever beam. The ablation process does not affect reflectivity of the mirrors of the EFPI, resulting in the high visibility of the interferometric fringe. The vibration can be interrogated by using the quadrature passive demodulation. The experimental results show that the sensitivity of 20.678 mV/g@500 Hz is achieved in the acceleration range of 0-10 g. The frequency response of the ANSYS simulation and the experimental results are compared with the frequency range from 100 Hz to 3000 Hz, and the resonant frequency is 1920 Hz.