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Fabrication of long period fiber gratings based on embedded-core hollow optical fiber

We propose and experimentally demonstrate a novel long period fiber grating (LPFG) in an embedded-core hollow optical fiber (ECHOF). Without the structural deformation of the air hole and the fiber core, the high-quality LPFG can be fabricated within a few scanning cycles by a high-frequency CO2 laser with a low energy density of 0.896J/mm2. The ECHOF LPFG reveals a high temperature sensitivity of 50.2 pm/°C and a low strain sensitivity of 0.4 pm/με. Due to the good performance and easy fabrication, the ECHOF LPFG will be important to develop novel in-fiber devices.