Writing of Apodized Phase-Shifted Long-Period Fiber Gratings With a Computer-Controlled CO $_{2}$ Laser

We apply a $hbox{CO}_{2}$ -laser writing method to the fabrication of sophisticated long-period fiber grating (LPFG) filters. The method allows the position of the writing beam to be computer-programmed to produce the required grating profile without using any mask. We demonstrate the flexibility and the controllability of the method with a number of apodized phase-shifted LPFGs written in a germanium–boron codoped fiber.