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 degrees C. Results of a comparison of grating characteristics for the two fibers are presented. (C) 1999 Elsevier Science B.V. All rights reserved.