CO2-Laser Induced Long-Period Fiber Gratings in Nano-Engineered Bend Insensitive Single-Mode Fiber

Long-period fiber gratings (LPFGs) written in nano-engineered bend insensitive single-mode fiber (NEBI-SMF) were reported. It is found that, only when the pitches of the gratings are in two wavelength ranges (270-305 mu m and 420-480 mu m), obvious resonance peaks can be obtained within the band of 1200-1650 nm, due to the cladding mode separation caused by the nano-engineered ring in the fiber cladding. The strain sensitivity of the LPFG with a pitch of 295 mu m in the range of 270-305 mu m is 2.8 pm/mu e, while the LPFG with a pitch of 470 mu m in the range of 420-480 mu m is insensitive to strain. The temperature sensitivities of the two LPFGs are 0.145 nm/degrees C and 0.098 nm/degrees C, respectively. Due to the special structure of the NEBI-SMF, more interesting phenomenon could be explored by carrying out further theoretical and experimental study of these novel LPFGs, such as the bending and twisting characteristics, etc.