Fabrication of long superstructure fiber Bragg gratings (SSFBGs) using a novel scanning phase-mask technique

Superstructure (sampled) fiber Bragg gratings (SSFBGs) are attractive optical filters for optical communication and optical sensor systems, because of their comb-like filter response. The length of SSFBG is conventionally limited by that of the phase mask. However, the length of the high-quality phase mask fabricated by an interferometric technique is limited to similar to5 cm. In this paper, we propose a novel fabrication technique for long SSFBGs based on scanning phase masks and trimming relative phases between FBGs. This technique enables the fabrication of long SSFBGs with short phase masks. In the experiments, we successfully fabricated a 9-cm-long SSFBG by cascading three 3-cm-long SSFBGs.