Characterization of Fiber Bragg Grating Inscribed in Few-Mode Silica-Germanate Fiber

We present a temperature and strain fiber sensor utilizing fiber Bragg grating (FBG) inscribed in silica-germanate few-mode fiber. The temperature and strain sensitivities of resonant wavelength formed by mode LP01 self-coupling and mode LP01-LP11cross-coupling are investigated theoretically and characterized experimentally. Two resonant wavelengths demonstrate different temperature sensitivities of 11.5 pm/°C 10.6 pm/°C, respectively, due to different mode profile, while the strain sensitivities are quite similar with a value of 0.9 pm/με. By using FBG character matrix, the proposed fiber sensor can measure those two parameters simultaneously within a compact and cost-effective setup.