Acoustic emission sensor based on biconical fiber micro-tapers

A fiber optic sensor to detect acoustic emission is reported, which is based on a fiber taper incorporated in a fiber Mach- Zehnder (M-Z) interferometer as the sensing arm. Benefited from their micrometer sizes in transverse dimension, fiber tapers have higher sensitivity to the environmental vibrations compared with standard single mode fibers (SMFs). Under the same conditions, the thinnest fiber taper in this report with a diameter of 1.7 μm shows 22dB improvement in the signal to noise ratio (SNR) comparing that in SMF28. We also calculated the phase change of a fiber taper under longitudinal strain and the variation of phase changes with different diameters.