Optical fibre grating fabrication apparatus which minimizes diffraction effects

There is provided an optical fiber grating fabricating apparatus. To fabricate fiber gratings, an optical fiber (40,50) is prepared, a mask (42,52) with a predetermined period is spaced from the optical fiber (40,50), for forming patterns to be used in fabricating gratings on the optical fiber (40,50), a UV (Ultra Violet) light source projects UV light in a perpendicular direction to the optical fiber (40,50), a lens (46,56) focuses the UV light, and a mobile concave lens (44,54) diverges the focused UV light along the length direction of the optical fiber (40,50) and changes the period of the fiber gratings while moving to and from.