Long period fiber grating and high sensitivity refractive index sensor based on hollow eccentric optical fiber

We have demonstrated experimentally a long period fiber grating (LPFG) written in a hollow eccentric optical fiber (HEOF). A high-quality LPFG with no structural deformation was fabricated using a high-frequency CO2 laser with a low energy density of 0.896 J/mm2. The LPFG writing parameters showed only a weak dependence on orientation of the fiber core to the writing beam. The liquid-filled HEOF LPFG has a high refractive index sensitivity of 1005 nm/RIU over a refractive index range of 1.422–1.441. The good performance and easy fabrication of the HEOF LPFG indicate that it is a promising platform for novel in-fiber microfluidic devices.