A Compact Ultra-Long Period Fiber Grating Based on Cascading Up-Tapers

A new ultra-long period fiber grating constructed by a series of up tapers is proposed and demonstrated experimentally. A fiber grating with length of 2mm is fabricated by cascading three up-tapers on a single mode fiber, which is the shortest ultra-long period fiber grating up to now. The effect of periodic error is greatly reduced due to the ultra-long grating pitch. The fabrication repeatability is greatly improved by adopting semi-automated fabrication techniques. Strain and temperature are identified simultaneously by tracing the change of resonant wavelength and attenuation peak amplitude with a resolution of
$6.2~\mu \varepsilon $
and 0.2°C, respectively.