SRI-Immune Highly Sensitive Temperature Sensor of Long-Period Fiber Gratings in Ge–Sb–Se Chalcogenide Fibers

This work exhibits design and characteristic study of highly sensitive temperature sensors of long-period fiber gratings (LPFGs) in Ge–Sb–Se fibers. Temperature characterization of the designed LPFGs with different working modes, operating wavelengths, and surrounding refractive indices (SRI) were studied. Results showed that temperature sensitivity of the proposed Ge–Sb–Se LPFGs reached 0.5787 nm/ at 1.55 μm at the lowest LP ₀₂ cladding mode, which is approximately 12 times higher than silica LPFGs and 1.2 times higher than that of As–Se LPFGs. When grating period of the designed Ge–Sb–Se LPFG was selected at its dispersion-turning-point, temperature sensitivity reached a maximum absolute value of 24.715 nm/°C. Influences of operating wavelength and temperature sensitivity of these LPFGs on SRI are extremely weak due to relatively high refractive index of Ge–Sb–Se fiber, indicating that the designed Ge–Sb–Se LPFG temperature sensor possesses extremely strong sensing stability on SRI.