Optical fibre Mach-Zehnder Microphone

An optical fibre "microphone" was realised by configuring and mounting the sensing arm of a fibre Mach- Zehnder interferometer such that the acoustic waves could be picked up in the most efficient way. The set-up employed a 1550 nm 0.8 mW laser diode, two 50/50 fibre couplers, single mode optical fibre, a photo detector/pre-amplifier unit and a sound recorder. There was a good comparison between the fibre microphone and a low-end dynamic microphone. The sensor is immune to electromagnetic interference. Many applications are foreseen if the set-up can be made more compact.