Compact acoustic sensor based on air-backed mandrel coiled with optical microfiber

Abstract

We propose and demonstrate a compact acoustic sensor comprising a 2μm diam, 35mm length optical microfiber coiled around a 3mm diam air-backed mandrel. Acoustic waves induce local pressure variations that change the mandrel diameter and thus the optical path length of the mode propagating in the microfiber. The phase modulation is detected via a single-fiber polarimetric interferometer. The low stiffness and minimum bend radii of microfibers gives rise to extremely small package sizes without compromising acoustic responsivity.