In Reflection Metal-Coated Diaphragm Microphone Using PCF Modal Interferometer

Abstract

Starting from non-destructive testing to underwater surveillance, acoustic sensors are finding a variety of modern-day applications. In this article, we propose a double/hybrid interferometry optical microphone. We have combined the intermodal interference of SMF-SCPCF section with extrinsic Fabry-Perot interferometer to construct a highly sensitive, compact and robust optical microphone. The sensor head consists of an SMF-SCPCF spliced section placed in front of an aluminium coated nitrile diaphragm. The acoustic sensitivity and noise-limited minimum detectable pressure (MDP) of the proposed microphone is 34.8 nm/kPa and 0.26 P/√Hz at 1400 Hz. We also recorded the angular response of the proposed optical microphone and the final directionality pattern is of `cardioid' type which makes it a preferable option for a wide variety of applications.