High Torsion Sensitivity Sensor Based on LPFG With Unique Geometric Structure.

In this paper, we propose a sensor with high torsion sensitivity. This sensor has the ability to distinguish the torsion direction. A long-period fiber grating (LPFG) with a unique geometric structure is used to configure this sensor. The proposed LPFG is prepared by CO2 laser polishing method and etching method. First, we periodically polish the two opposite planes which are parallel to the axis direction of the fiber to get sheets structure. Then, the V-shaped grooves are etched on the surface orthogonal to the sheets to fabricate the proposed LPFG. Because the V-shaped grooves are arranged along the axis direction of the optical fiber, we name it by V-LPFG. This unique geometric structure results in the sensor with high torsion sensitivity. Experimental results prove that the torsion sensitivity of the proposed sensor reaches 0.399 nm/(rad/m) in the range of–10.5 rad/m to 10.5 rad/m. More importantly, the torsion sensitivity is significantly increased from 0.041 nm/(rad/m) to 0.399 nm/(rad/m) after the V-shaped grooves are etched. The temperature sensitivity of the proposed sensor is 50 pm/°C at the temperature range of 30–150 °C. Due to the high torsion sensitivity, relatively easy fabrication process and high price to quality ratio, the proposed sensor has the potential of carrying out torsion measurement with high sensitivity. [ABSTRACT FROM AUTHOR]