High sensitivity fiber-optic Michelson interferometric low-frequency acoustic sensor based on a gold diaphragm

• Published in: Optics express 2020-08, Vol.28 (17), p.25238-25249
• Main Authors: Fan, Pingjie, Yan, Wei, Lu, Ping, Zhang, Wanjin, Zhang, Wei, Fu, Xin, Zhang, Jiangshan
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.402099

A Michelson interferometric fiber-optic acoustic sensor based on a large-area gold diaphragm is proposed in this paper. The Michelson interferometer (MI) based on 3×3 coupler is comprised of two beams that reflected from the gold diaphragm and a cleaved fiber end face. Thickness and diameter of the gold diaphragm are 300 nm and 2.5 mm, respectively. Based on the phase difference between each output port of the 3×3 fiber coupler, an ellipse fitting differential cross multiplication (EF-DCM) interrogation process is induced for phase demodulation, which can overcome the phase distortion caused by property degradation of 3×3 coupler. Experimental results show that the sensor has a phase sensitivity of about -130.6 dB re 1 rad/μPa@100 Hz. A flat response range between 0.8 to 250 Hz is realized with the sensitivity fluctuation below 0.7 dB. Besides, the signal-to-noise ratio (SNR) and minimal detectable pressure (MDP) of the sensor are 57.9 dB and 10.2 mPa/Hz 1/2 at 5 Hz. The proposed sensor exhibits superiorities of compact size, high sensitivity, flat low-frequency response and ease of mass production, which gives the sensor great potential for low-frequency acoustic sensing and photo-acoustic spectroscopy.