Diaphragm-based optical fiber sensor array for multipoint acoustic detection.

Multipoint acoustic sensing system plays an important role in industrial applications. Here, a diaphragm based optical fiber sensor array is proposed, in which each sensor tip is made of 10-layer graphene diaphragm and optical fiber pigtail, with the compact size of about 2.5 mm in diameter. In particular, coherent phase detection is adopted to improve detection signal-to-noise ratio (SNR) and eliminate the demodulation dependence on structural parameters of sensor tips, and thus to achieve the multiplexing ability. Through time division multiplex (TDM), a multiplexing capacity up to 248 in theory can be realized, which is the first time to theoretically demonstrate large-scale acoustic sensor array for diaphragm based fiber sensor by phase detection, to the best of our knowledge. A prototype of 2 *2 sensor array is built to demonstrate the acoustic sensing performance. The field test results show excellent acoustic sensitivity of higher than -136 dB re 1 rad/μPa within the frequency range of 300 Hz~15 kHz, as well as the MDP of only 75 μPa/Hz. Besides, good temperature stability and wide directivity are demonstrated. The proposed sensor array is promising in sound source localization, where the positioning accuracy of 3.55 cm is successfully realized.