Self-calibrated non-contact fibre-optic Fabry–Perot interferometric vibration displacement sensor system using laser emission frequency modulated phase generated carrier demodulation scheme

In this paper, the principle of a self-calibrated non-contact fibre-optic Fabry–Perot interferometric vibration displacement sensor (FOFPIVDS) system is described and experimentally demonstrated. According to the principle, the Fabry–Perot cavity, constituted by placing the end face of a gradient-index lens in parallel with the measured vibration surface, is used to translate the vibration displacement of the measured vibration surface into phase shifts in the interference signal output from the FOFPIVDS, and the laser emission frequency modulated phase generated carrier (FMPGC) demodulation scheme based on the arctangent (Arctan) algorithm is adapted to demodulate the phase shifts. After eliminating the optical power modulation in the laser emission frequency modulation, the sensing model for the FOFPIVDS system using the FMPGC–Arctan demodulation scheme is established. On these bases, the FOFPIVDS is designed and fabricated, and the prototyping FOFPIVDS system is built and experimentally tested. The research results indicate that the fabricated FOFPIVDS system possesses the characteristics as follows: (1) the sensitivity is only determined by the laser wavelength and the vibration displacement measurement is self-calibrated, (2) the nonlinearity is 0.29% and (3) the resolution is less than 2.06 nm.