Fiber Bragg gratings are used in a wide variety of devices including sensors, tunable filters, and signal controllers for Wavelength Division Multiplexing. Bragg gratings can be formed in an optical fiber by illuminating the fiber from the side with a pattern of ultraviolet light. Most gratings are made using 240-nm light. However, by using 330-nm light the grating can be written right through the standard polymer coating of the fiber, which preserves the fiber's mechanical strength. We discuss some of the mechanisms that degrade the strength of fiber gratings. We also discuss applications of mechanically strong fiber gratings, including very wide (> 50 nm) tunable filters.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.