Influence of molten-state duration time on torsion sensitivity for fiber sensors based on helical long-period gratings: An experimental study

Abstract

Abstract In this paper, we report an experimental study to systematically and quantitatively investigate the effect of molten-state duration time (MSDT) upon the torsion sensitivity for fiber sensors based on helical long-period fiber gratings (H-LPGs). During the fabrication processes to twist the standard single-mode optical fibers (SMFs) in molten states, we have found that there exists a logarithmic function relationship between the sensitivity of H-LPG-based torsion sensors and the manufacturing MSDT. When the average MSDT to fabricate each grating period increases from 24 to 72 s, the torsion sensitivity increases from minimally 0.0735 nm/(rad/m) to maximally 0.1105 nm/(rad/m) within a twist rate of −20.9 to +20.9 rad/m. This empirical study can potentially provide a constructive guideline for the fabrication and testing of H-LPG-based fiber torsion sensors.