A Highly Sensitive Curvature Sensor Based on Omega-Shaped Long-Period Fiber Grating

compact omega-shaped long-period fiber grating (OS-LPFG) for vector bending measurement is proposed and investigated in this article. This sensor is fabricated by periodically splicing single-mode fiber (SMF) and multimode fiber (MMF) into omega shape to get the purpose of sensitivity enhancement. The proposed OS-LPFG can distinguish the bending direction and achieves the curvature sensitivities in X-, Y-, and -X-directions are 12.03, -69.95, and -19.84 nm/m(-1) at the range of 0-1.5 m(-1), respectively. Meanwhile, the sensor has a small temperature crosstalk of 0.0011 m(-1)/degrees C at the temperature range of 20 degrees C-110 degrees C. In addition, the sensor features a compact structure with the length of 1.5 mm due to the strong refractive index (RI) modulation induced by fabricating method, which proposes a feasible idea for compact fiber curvature sensor design.

Automated summary

This article proposes and investigates a compact omega-shaped long-period fiber grating (OS-LPFG) for vector bending measurement. The OS-LPFG can distinguish bending direction and achieve curvature sensitivities in X-, Y-, and -X-directions of 12.03, -69.95, and -19.84 nm/m(-1) in the range of 0-1.5 m(-1), respectively. Additionally, the sensor has a small temperature crosstalk of 0.0011 m(-1)/°C in the temperature range of 20°C-110°C. The compact structure of the sensor with a length of 1.5 mm is achieved through the strong refractive index (RI) modulation induced by the fabrication method, providing a feasible idea for compact fiber curvature sensor design.