Amplitude multiplexing of Mach-Zehnder interferometer array and its application to locating acoustic emission

We report an amplitude division multiplexed interferometric sensor array for locating acoustic emission. The interferometer is composed of 3 arms, the two sensing arms have different interference amplitude with the reference arm, so we can judge whether a sensor receives sound or not from the composite interference amplitude. For single sound source, the sound-receiving delay of two sensors can be obtained from the time when the interference amplitude changes, and the sound source location relative to the sensors can also be achieved in a 1-D system. Preliminary experiments were carried out and demonstrated a one-dimensional (1-D) location accuracy of better than 1cm. The system can be extended for 2-D and 3-D location of acoustic emissions by adding one or two more sensing arms, respectively, in the interferometer.