Optical fiber ultrasonic sensor based on partial filling PDMS in hollow-core fiber

A compact optical fiber ultrasonic sensor based on Fabry-Perot (FP) interferometer is proposed and demonstrated. The sensor consists of a single-mode fiber (SMF) spliced with a short section of hollow-core fiber (HCF), in which HCF is partially filled in polydimethylsiloxane (PDMS) to construct FP cavities. An economy two-step amplification-based demodulation system is built for ultrasonic wave detection. Attribute to the excellent elastic properties of PDMS, vibration generated by ultrasonic stimulation is enhanced, so as to modulate the air cavity and achieve ultrasonic wave detection. Meanwhile, integrated probe in single fiber combined with PDMS filling technique provide sensitive detection of ultrasonic wave, further improving the sensor's stability and durability. Low cost, simple fabrication, high signal–noise ratio, and wide frequency response, make the sensor has a broad application prospect in ultrasonic sensing.