Strong fiber Bragg grating fabrication by hybrid 157- and 248-nm laser exposure

A permanent 248-nm photosensitivity response was locked into hydrogen-loaded standard telecommunication fiber by uniform 157-nm F2-laser pre-exposure. Strong (>30 dB) fiber Bragg gratings were efficiently generated after hydrogen out-diffusion, improving the thermal stability. The 157-mn radiation produced weakly absorbing Si-OH and Ge-OH absorption bands at 1.39-μm.