Asymmetrically Corrugated Long-Period Gratings by Burning Fiber Coating and Etching Cladding

A novel method to form asymmetrically corrugated long period fiber gratings (LPFGs) by periodically scanning the unstripped optical fiber using the high-frequency CO
₂
laser under side illumination as well as HF etching processing has been proposed and demonstrated in this letter. Microbends exist in the asymmetric structures when tensile force is applied that greatly enhance the refractive index modulation. Several asymmetrically corrugated LPFGs with a grating pitch of 600 μm are fabricated. A linearly step-changed period chirped corrugated LPFG has also been fabricated that well proves the flexibility of this method in fabricating nonuniform corrugated LPFGs.