Using Frequency-Shifted Interferometry for Multiplexing a Fiber Bragg Grating Array

We demonstrate a fiber Bragg grating (FBG) sensor multiplexing scheme based on frequency-shifted interferometry, in which a frequency-shifting element is placed asymmetrically in one arm of a folded Mach-Zehnder interferometer. The location and the reflection spectrum of each FBG sensor in an array can be resolved through Fourier transform. We experimentally investigated this multiplexing scheme in an FBG array constructed by ten low-reflectivity (~4%) sensors. A signal-to-noise ratio of 48 dB was achieved with crosstalk below 34 dB.