PRODUCTION OF FIBER GRATING AND THE FIBER GRATING

PROBLEM TO BE SOLVED: To make transmission characteristics and mechanical strength characteristics compatible, without impeding the improvement of the productivity. SOLUTION: On an optical fiber 1' consisting of a core and a cladding, a coating layer 45 of 37.5 μm in film thickness is formed in a single coat by the use of ultraviolet-ray transmission resin. This coated optical fiber 1 is positioned so that the cladding layer has its outer peripheral surface inscribed in the external edge of the beam pattern BP of ultraviolet laser light which converge on a focus F by a cylindrical lens system 7. A Bragg grating is written to the core by having the core irradiated with an ultraviolet laser beam of 1.5 kJ/cm in the irradiation energy density from outside the jacket layer via a phase mask.