Analysis on intensity demodulated strain sensing based on multiple phase-shifted FBG

An intensity demodulated strain sensing scheme based on multiple phase-shifted fiber Bragg grating (FBG) is investigated. Wavelength shifts related to the external strain signal will result in various power change received by the photodetector. The reflected spectrum of the sensing multiple phase-shifted FBG are designed using the transfer matrix method to and fabricated by dithering phase mask method. The strain sensing scheme is analyzed numerically by relate the power change to reflectivity spectrum, thus help us optimize the design and fabrication of multiple phase-shifted FBG to achieve maximum sensitivity. The experimental results show that the strain sensitivity can be significantly enhanced by over 10dB by using phase-shifted FBG with many phase shifts compared to a normal FBG.