Optical Fiber Acoustic Sensor Based on Nonstandard Fused Coupler and Aluminum Foil

An optical fiber acoustic sensor based on nonstandard fused coupler and aluminum foil is proposed and experimentally demonstrated. Acoustic vibration is measured by detecting the insertion loss of the nonstandard fused coupler. As the number of the coupling cycle increases, sensitivity of the multicycle fused coupler-based sensors to acoustic vibration could be improved. Under the same experimental conditions of input light power
${\sim}{\rm 10}~{\rm dBm}$
and acoustic pressure level
${\sim}{\rm 59}~{\rm dB}$
, this assumption was experimentally conformed with results of 0.18 mW/Pa (1 cycle), 0.65 mW/Pa (3 cycles), and 1.71 mW/Pa (5 cycles), respectively. In addition, multimode fused coupler-based sensor shows sensitivity of 2.63 mW/Pa, in the frequency range from 20 Hz to 20 kHz and with average signal-to-noise ratio about 20 dB. This sensor may have potential applications in future fiber optic microphone.