Demodulation of EFPI-FBG Hybrid Optical Microphone Based on Spectrum Analysis
Bin Liu, Ruijia Liang, Hui Deng, Yan Wang, Lei Yan, Lei Liu, Lei Yu, Mingguang Shan, Zhi Zhong
Abstract
Based on spectrum analysis technology, a fast demodulation method is proposed to sense the acoustic and temperature with EFPI-FBG hybrid optical microphone accurately. Separating the EFPI and FBG spectrum from the obtained EFPI-FBG superimposed spectrum, frequency estimation based on total phase method and peak-searching based on quadratic polynomial fitting method were adopted to calculate the F-P cavity’s length and the central wavelength of the FBG. The detailed simulation showed that the proposed method has the capabilities to detect the change of the F-P cavity’s length and the drift of the FBG’s central wavelength with a high speed and accuracy. By applying the proposed method to a homemade diaphragm-based EFPI-FBG hybrid optical microphone, the acoustic and temperature could be recovered successfully. The acoustic sensing error caused by the temperature could be reduced from 75% to 10%.