Arrayed waveguide grating-based high-frequency ultrasonic sensors

Arrayed waveguide grating (AWG) has been widely used as a multiplexer in FBG demodulation system because of its high stability, low loss and fast read-write ability. They substitute expensive and vibration fragile spectrometers. In this paper, we compare two kinds of AWG demodulation systems experimentally. One is a multi-channel ultrasonic sensor system using fiber ring laser based on erbium-doped fiber amplifier (EDFA) and arrayed waveguide grating (AWG) as the intensity demodulator. And another is a one-way amplified system based on EDFA. When the external dynamic strains are applied on the FBG sensor, the central wavelength of the FBG will move between two adjacent channels of the AWG. Therefore, the modulation of the central wavelength of the FBG is converted to the amplitude modulation of the output of the two adjacent channels. Experimental results show that the multi-channel ultrasonic sensor system of one-way amplified configuration based on EDFA is more stable and can test high-frequency dynamic strain stably. The ultrasonic signal in water is successfully detected through one-way amplifier configuration.