Ultrasonic location using the Sagnac interferometric optical fiber sensor in underwater

In this work, an optical fiber sensor(OFS) system utilizing principle of Sagnac interferometry was designed and tested to detect the locations of ultrasonic signals in underwater. As a sensing component, the hollowed cylindrical mandrel wound by single mode optical fiber was used. The ultrasonic signal source was simulated by the PZT actuator operated by an function generator. The distance dependency of the OFS's sensitivity was measured. It has been shown that the OFS could detect the signals less affected by ultrasonic path comparing to conventional acousto-electric sensor, and accurate location of ultrasonic signal could be carried out using two and three OFSs.