Enhanced growth rate for Bragg grating formation in optical fibers with titania-doped outer cladding

Bragg gratings are written in two identical, communications-grade optical fibers, one of which has a layer of titania-doped outer cladding. Continuous-wave laser at 244 nm and 40 mW power is used. Gratings can be written in fibers with titania-doped outer cladding after just 1 day of exposure to hydrogen at 60 atm pressure. A similar exposure to hydrogen for 4 to 5 days is required before gratings can be written in fibers without titania-doped outer cladding. This difference is observed to be due to partial absorption of 244 nm light by titania, resulting in heating of the fiber to 200 °C. Results of a comparison of grating characteristics for the two fibers are presented.