Quasi-Distributed IFPI Sensing System Demultiplexed With FFT-Based Wavelength Tracking Method

In this paper, we fabricated a quasi-distributed intrinsic Fabry-Perot interferometric (IFPI) sensing array with the femtosecond laser. Each IFPI sensor is constituted by a pair of laser-induced internal reflectors and has a different cavity length. After multiplexing, IFPI sensors can be distinguished in the frequency domain for their different free spectral ranges. Next, a fast-Fourier-transform-based wavelength tracking method was proposed to demodulate the sensing signal. With a specially designed digital filter, frequency components corresponding to each sensor are extracted from the transmission spectra and are transformed back to the wavelength domain. Then the wavelength tracking method is utilized to demodulate the temperature information applied on the individual sensors. Experimental results show that the multiplexed sensors have good consistency and the temperature sensitivity is 11.24 pm/°C.