FBG-FP spectral denoising for high resolution of quasi-static strain measurement based on EMD

Noises in the reflection spectra of fiber Bragg grating (FBG) typically limit the resolution of quasi-static strain sensor based on FBG. This paper introduces a new spectral noise suppression method based on empirical mode decomposition (EMD). The spectral noise suppression method is used to denoise reflection spectra from a pair of FBG-based Fabry-Perot interferometers (FBG-FPs) for achieving high static-strain resolution. The EMD is proposed for extracting adaptive basis functions called Intrinsic mode functions (IMFs) from two FBG-FPs' reflection spectra. The spectral noise suppression method involves thresholding every IMF and reconstructing the spectra using the processed IMFs. After thresholding the IMFs, we use the cross-correlation algorithm as the peak detection technique for quasi-static strain demodulation. The demodulation results of the EMD-Soft method, cross-correlation method in wavelet domain and the traditional cross-correlation method are compared. The quasi-static strain resolution achieved by the proposed EMD-Soft method is nearly five times higher than the traditional cross-correlation method.