RI Ring Laser Sensor Based on Concatenating CLF and SMF With One Core-Offset Joint

In this letter, a novel all-fiber ring laser refractive index (RI) sensor is proposed and experimentally demonstrated. Such sensor is obtained by inserting a segment of cladding-less fiber between two sections of single-mode fiber with one core-offset joint, which is designed to enlarge the extinction ratio. With the help of ring laser sensing system, a 3-dB bandwidth below 0.2 nm and an optical signal-to-noise ratio near 30 dB can be achieved. Meanwhile, the high output power and the side-mode suppression ratio of the sensor are presented. Experimental results show that the RI sensitivity is 52.3 nm/RIU in the RI range of 1.334-1.370. The sensor also has the advantages of simple structure and low cost, preforming potentials in large-scale productions.