Demodulation of diaphragm based acoustic sensor using Sagnac interferometer with stable phase bias
- 30 October 2015
- journal article
- Published by Optica Publishing Group in Optics Express
- Vol. 23 (22), 29268-78
- https://doi.org/10.1364/oe.23.029268
Abstract
A stable phase demodulation system for diaphragm-based acoustic sensors is reported. The system is based on a modified fiber-optic Sagnac interferometer with a stable quadrature phase bias, which is independent of the parameters of the sensor head. The phase bias is achieved passively by introducing a nonreciprocal frequency shift between the counter-propagating waves, avoiding the use of complicated active servo-control. A 100 nm-thick graphite diaphragm-based acoustic sensor interrogated by the proposed demodulation system demonstrated a minimum detectable pressure level of ~450 μPa/Hz1/2 and an output signal stability of less than 0.35 dB over an 8-hour period. The system may be useful as a universal phase demodulation unit for diaphragm-based acoustic sensors as well as other sensors operating in a reflection mode.Department of Electrical EngineerinFunding Information
- Hong Kong Polytechnic University (PolyU) (G-YM16)
- National Natural Science Foundation of China (NSFC) (61290313)
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