Sensitivity-Enhanced Strain Sensor With a Wide Dynamic Range Based on a Novel Long-Period Fiber Grating

A long period fiber grating prepared by multimode fibers (MMF-LPFG) is proposed and experimentally demonstrated as a sensitivity-enhanced strain sensor. The core diameter mismatch between the MMFs excites the high order cladding mode to obtain a compact sensing structure (3.6 mm). The strain sensitivity of the MMF-LPFG structure is enhanced to −15.06 pm/
$\mu \varepsilon $
when the grating period is closer to the dispersion turning point (DTP). Meanwhile, the novel fiber structure also has an excellent mechanical property to achieve a large dynamic range (
$\text{0-4508} ~\mu \varepsilon $
) in strain measurement.