Demodulation of acoustic signals in fiber Bragg grating ultrasonic sensors using arrayed waveguide gratings

In this study, we propose a demodulator for fiber Bragg grating (FBG) ultrasonic sensor array using arrayed waveguide grating (AWG). Wavelength modulation in the FBG center wavelength due to ultrasonic sound pressure is transformed to light intensity modulation at the AWG output channels using the slopes of the AWG pass band. We experimentally demonstrate demodulation on the basis of the proposed principle for an FBG immersed in an ultrasonic cleaner. The effects of the relationship between the center wavelengths of FBG and AWG on demodulated signals are investigated in the experiments.