The hydrogen loading system is used to diffuse H 2 gas molecules into the fibre core at high pressure. Among these sensors, hydrogen sensors consisting of fiber grating coated with sensitive materials have attracted intensive. The hydrogen loading process can achieve ultrahigh UV photosensitivity in conventional Ge doped telecommunication fibres. Our experimental result shows that these gratings maintained more than 60% of their. The threshold for the fabrication of fiber Bragg gratings with ultrafast 800-nm radiation and a phase mask was studied in SMF-28 and all-silica core fiber by use of 125-fs pulses.