Glass structure changes in CO₂-laser writing of long-period fiber gratings in boron-doped single-mode fibers

We investigate in detail the process of CO₂-laser writing of long-period fiber gratings (LPFGs) in unannealed and annealed boron-doped fiber samples by using repeated scanning of CO₂ -laser pulses. We find that the writing dynamics depends strongly on the CO₂-laser energy density and the annealing temperature of the fiber. Our results from analyzing the writing dynamics reveal the relative importance of various physical effects arising from glass structure changes due to different writing conditions and thus provide a better understanding of the formation and the properties of CO₂-laser written LPFGs. © 2009 IEEE.