Fabrication of Axially Symmetric Long-Period Gratings With a Carbon Dioxide Laser

We demonstrate a simple but effective method of creating an axially symmetric refractive index change in an optical fiber using the infrared beam from a carbon dioxide laser. Symmetric exposure of the fiber is achieved by using a single incident laser beam and placing a special reflector behind the fiber. Long-period gratings produced with this method exhibit clean spectra and very low insertion loss (<0.1 dB), similar to those induced by ultraviolet light