Ultrasensitive Strain Sensor Based on Core-Bending Long Period Fiber Grating

In this letter, a novel core-bending long period fiber grating (CB-LPFG) based on symmetrical polished fiber plane is designed and experimentally testified. By employing methods of CO2-laser polishing and oxyhydrogen flame heating, periodic bending cores are achieved on a symmetrical polished plane. Due to the reduction of the cladding and the bent core, the sensitivity of the structure is strongly enhanced. Experimental results present that the highest strain sensitivity of CB-LPFG with 7 periods reaches -0.846 nm/
$\mu \varepsilon $
. To the best of our knowledge, is firstly increasing the strain sensitivity of fiber sensor based on single-wavelength demodulation to nm/
$\mu \varepsilon $
level. Meanwhile, the temperature sensitivity of CB-LPFG is 236 pm/°C with dynamic range of 30-
$130~^{\circ }\text{C}$
. Consequently, the proposed sensor is expected to offer significant potential to detect micro-deformation more precisely.