Periodically tapered long-period fiber gratings by CO2 laser heating and tension stretching

Periodically tapered long-period fiber gratings (LPFGs) are demonstrated by using CO₂ laser heating with a cylindrical lens and periodically scanned along the fiber axis on a tensioned standard single-mode fiber. The depth of periodic relief on the fiber surface depends on the writing time as well as the grating period. The LPFG has perfect axial symmetric tapered shape that is helpful for achieving polarization independent properties.