Fabricating technology of fiber grating with phase masks

When excimer laser irradiate phase masks, the periodic fringe patterns are formed in near field, exposing fiber to it, in core gratings can be induced. Using the coupled mode theory, we deduce the reflected power of the fibre grating with a reasonable assumption of the refraction index distribution. Relationships between the reflected power and relevant fibre parameters are discussed. And influence factors of fiber gratings fabricating are analysed. We gain the conclusions that the suitable refraction index modulation and long grating length are needed for making the narrow bandwidth and high reflected power fiber gratings. The near field intense distribution of the phase mask back surface and period formulas of fiber gratings are obtained.