Underwater acoustic sensor based on microfiber knot resonator

In this paper, a water acoustic sensor based on a microfiber knot resonator is proposed. It utilizes microfiber technology, resulting in a smaller sensor size and excellent detection capability for low-frequency signals. By developing suitable packaging techniques to protect the sensor, it becomes more suitable for underwater detection environments and increases the stability of the device. Polydimethylsiloxane (PDMS) has a lower refractive index than silicon dioxide and exhibits good transmission performance. PDMS is used for encapsulation on both the top and bottom of the fabricated microfiber knot resonator, which improves its Q-factor and provides better protection for the resonator underwater. We employ filtering and amplification techniques to demodulate the received sound signals. The test results demonstrate that the sensor has an average sensitivity of −135.8 dB within the frequency range of 10 Hz to 2 kHz and an average signal-to-noise ratio of 53.2 dB. At 400 Hz, the sensitivity reaches −113.6 dB, with a signal-to-noise ratio of 80 dB.