Large-range torsion sensor based on twin-core polymeric optical fiber

In this study, we present the first fabrication of a ZEONEX-based polymer optical fiber (POF) with a twin-core structure for torsion measurements. The POF consists of a center and side core arrangement and its torsion performance was characterized using a pair of 5-mm fiber Bragg gratings (FBGs) inscribed in the cores using a 248 nm KrF excimer laser. The torsion was measured using the difference in the Bragg wavelength shifts between the two FBGs, which enabled torsion measurements independent of any temperature or strain variations. Torsion performance of the proposed sensor was evaluated in terms of operating range and torsion sensitivity by comparing it with that of another torsion sensor constructed with a commercial silica multi-core fiber. The POFbased torsion sensor was found to have superior operating range and sensitivity due to the low Young's modulus and flexible nature of the POF. A twist rate ranging from -538 to 538 rad/m and a torsion sensitivity of - 3.3 pm/(rad/m) were obtained for the POF-based torsion sensor, while the working range of a silica multi-core fiberbased torsion sensor was only from 0 to 144 rad/m, and a lower torsion sensitivity of - 0.34 pm/(rad/m). These results demonstrate the remarkable performance of the POF-based torsion sensor, making it an ideal candidate for applications demanding high twist rates.