다양한 외부 물리량 측정을 위한 사냑 간섭계 기반 광섬유 센서에 관한 연구

Abstract

In this thesis, the Sagnac birefringence interferometer based optical fiber sensors are proposed for measurement of various external physical quantities. The types of the proposed sensors are an optical fiber hydrogen sensor, pressure sensor, and strain sensor, which are able to measure the concentration of hydrogen in the air, pressure around the sensor head, and tension applied to the sensor head, respectively. In the case of the optical hydrogen sensor, due to the use of polarization-maintaining fiber (PMF) coated with palladium (Pd) whose thickness is ~400 nm as a sensor head, the proposed fiber hydrogen sensor is more durable and highly resistant to external stress applied on a transverse axis of an optical fiber, compared with other hydrogen sensors based on side-polished fibers or fiber gratings. The optical fiber pressure sensor is proposed by incorporating a polarization-diversity-loop-based Sagnac interferometer (PDLSI) composed of PMF and a fiber Bragg grating. The maximum pressure sensitivity was approximately -15.07 nm/MPa over a measurement range of 0-0.3 MPa. This is about four times higher than the maximum sensitivity reported in other fiber pressure sensors. In the optical fiber strain sensor, short polarization-maintaining photonic crystal fiber (PM-PCF), the length of which was ~2.0 cm, was employed as a sensor head. The length of the PM-PCF was reduced approximately by half, compared with the shortest one in the previous works.