Sensing Characteristics of Long Period Fiber Grating Written in Graded Index Fiber by CO2 Laser

We present a long period fiber grating, which can measure temperature, curvature, refractive index, torsion, and the corresponding sensitivities are 500.71 pm/°C,
$- {16}{{.53\ nm/}}{{\mathrm{m}}^{ - 1}}$
, -2776.19 nm/RIU, and -193.65 pm/(rad/m), respectively.