CO2 laser writing of long-period fiber gratings in optical fibers under tension

We demonstrate experimentally that the efficiency of writing a long-period fiber grating in a single-mode fiber by CO₂ laser pulses increases significantly with the axial stress applied along the fiber. We attribute the enhancement in writing efficiency to the generation of nonuniform inelastic frozen-in strains across the fiber under tension by CO₂ laser heating. Controlling the axial stress distribution along a fiber during the CO₂ laser writing process thus provides an additional degree of freedom for control of the grating characteristics. © 2008 Optical Society of America.