High sensitivity diaphragm-based extrinsic Fabry-Perot interferometric optical fiber underwater ultrasonic sensor

Optical fiber sensors for ultrasonic signals detection have become a research focus in the past years. In this paper, a novel structure of the diaphragm-based extrinsic Fabry-Perot interferometric (DEFPI) optical fiber ultrasonic sensor with a through vent hole of the fused silica ferrule was present. In this sensor system, the amplified spontaneous emission (ASE) optical source and the Fabry-Perot filter are used to adjust the wavelength of the operation point of the sensor. We performed the ultrasonic distance detection experiment from 1 cm to 31 cm and the sensor sensitivity experiment, and the pressure sensitivity of the sensor is 9.68 nm/kPa (66.69 nm/psi). The sensitivity of the fusion silica structure DEFPI optical fiber is much higher than that of the HCPCF-ILFP (hollow-core photonic crystal fiber in-line fiber-optic Fabry-Perot) and the fiber Bragg grating (FBG).