Highly sensitive directional torsion sensor based on a helical-tapered panda fiber

Abstract A directional torsion sensor based on Panda-type polarization-maintaining fiber (PMF) was experimentally demonstrated by using the arc technique, the helical-tapered modulates the PMF periodically, forming the helical-tapered long-period fiber gratings (Ht-LPFGs), in which torsion sensitivity was significantly enhanced by helical tapered structure. The experimental results show that the torsional sensitivity of Ht-LPFGs is 154.5 pm/(rad/m) and −0.008737 dB rad −1 m −1 . Ht-LPFGs’ sensitivity is one order of magnitude higher than that of tapered long-period fiber gratings (t-LPFGs) without helical structure. The torsion sensor proposed in this paper has the advantages of high sensitivity, low cost and small size, which provides a promising method for torsion measurement.