Curvature Sensing Setup Based on a Fiber Laser and a Long-Period Fiber Grating

In this letter, a curvature sensing setup based on a fiber ring laser containing a long-period fiber grating (LPFG) is presented. The LPFG operates as a wavelength selective filter and as a curvature sensing head. The LPFG consists of a periodically tapered fiber section written by a CO2-laser glass processing system. The experimental results show that by increasing the curvature values from 0 to 0.266 $\text{m}^{-1}$ , the laser wavelength emission shifts linearly from 1572 to 1560 nm, and a curvature sensitivity of −42.488 nm/ $\text{m}^{-1}$ is achieved. In addition, the laser emission has a linewidth of 0.05 nm, a slope laser efficiency of 0.43%, and a high single-mode suppression ratio (SMSR) of 60 dB. Finally, this fiber laser offers output power stability at room temperature, compactness, and robustness.