Design and development of a fibre-optic microphone

Kennedy, Isaac (2014) Design and development of a fibre-optic microphone. [USQ Project]


Download (3MB) | Preview


Due mainly to the fact that fibre-optic sensors are typically more expensive than conventional electronic sensors, fibre-optic sensing remains a somewhat obscure field. Fibre-optic sensors do have significant advantages such as electromagnetic immunity and corrosion resistance, and find their place in applications where electronics cannot be used (Kersey 1996). The aim of this project is the design and construction of a fibre-optic microphone, the proposed application for which is photoacoustic spectroscopy.
The theory behind fibre-optics, fibre-optic sensors, and interferometry is explored to provide a background for the project. Examination of the concept of photoacoustic spectroscopy reveals how this application affects the requirements of the microphone. Specifically, the microphone must be able to lock to a specified frequency and respond with an amplitude proportional to the volume of an audio tone at this frequency.
Based on its relatively high sensitivity and the simplicity of construction from fibre-optic components, it is determined that the Mach-Zehnder is the best suited interferometer for the fibre-optic microphone. A design is proposed on the Mach-Zehnder interferometer and is constructed using fibre-optic components. A lock-in amplifier's ability to lock to a specific frequency is well suited to the requirements of photoacoustic spectroscopy and is incorporated in the design as a means of extracting the microphone output.

Testing of the device produced promising results. The response of the fibre-optic microphone as measured by the lock-in amplifier is exponentially proportional to the volume of the tone used to test it. This proves the concept of the fibre-optic microphone and shows that it is fit for use in photoacoustic spectroscopy.

Statistics for USQ ePrint 27102
Statistics for this ePrint Item
Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering project.
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 Jul 2013 - 31 Dec 2021)
Supervisors: Leis, John
Date Deposited: 16 Sep 2015 02:12
Last Modified: 11 Feb 2016 03:37
Uncontrolled Keywords: fibre-optic, microphone, interferometry
Fields of Research (2008): 09 Engineering > 0906 Electrical and Electronic Engineering > 090603 Industrial Electronics
Fields of Research (2020): 40 ENGINEERING > 4009 Electronics, sensors and digital hardware > 400907 Industrial electronics

Actions (login required)

View Item Archive Repository Staff Only