CHARACTERISTICS OF HYDROGENATED FIBER BRAGG GRATINGS

By utilizing both hydrogen loading for photosensitivity enhancement an d a phase mask for holographic exposure, we have fabricated fiber Brag g grating with controllable reflectance and bandwidth, The evolution o f hydrogen diffusion into a single-mode optical fiber before exposure, and out of the fiber after exposure was characterized, and the result s were consistent with the theoretical modeling. The shifting of Bragg wavelength and thermal reliability were found related to the hydrogen behavior inside the fiber, One solution to prevent Bragg wavelength f rom drifting after the grating was formed and hence to increase the gr ating's reliability was to anneal it so that the residual hydrogen was forced out of the optical fiber in a short time.