Interferometer based demodulation technique of phase shifted fiber Bragg grating sensor for acoustic signal sensing

Grating based sensors are ideal candidates for strain and temperature measurement. Many researchers have already anticipated detecting low strain signal by using an fiber Bragg grating (FBG) sensor instead of the conventional lead- zirconatetitanate (PZT) sensor due to the benefits of the FBG together with flexibility, immunity from electromagnetic interference, corrosion resistance, small size, ability to be embedded, and multiplexing capabilities [1]. Especially, FBG sensors are playing a noteworthy role towards the detection of low amplitude dynamic signal. Therefore, there are two essential necessities for detecting low strain signal: broad bandwidth and high sensitivity. FBG is not capable to detect low strain signal because if the wavelength of low strain signal is much lesser than the Bragg wavelength, no change will arise in FBG reflection spectrum. Towards this direction, many researchers developed phase shifted grating based ultrasonic sensors to achieve broader bandwidth and superior sensitivity.