Method for manufacturing optical fiber grating, optical fiber grating, and fiber laser

A method for manufacturing an optical fiber grating that includes first and second gratings that configure an optical resonator, the method comprising:

• forming the first grating by radiating ultraviolet light to an optical fiber so that a irradiation intensity Z satisfies the following Equation 1:
• Z≦(ΔλS/x+0.04556Y2+1.2225Y)/(0.05625Y2+1.6125Y) Equation 1,
• where, Z represents an irradiation intensity (mJ/mm2) of the ultraviolet light, ΔλS represents the maximum shift amount of a reflection center wavelength of the first grating that is allowed as long as reflection wavelengths of the first grating and second grating overlap each other, x represents a shift amount of the reflection center wavelength per temperature change of 1° C. (nm/° C.) in the first grating, and Y represents an intensity (W) of the wave-guided light;
• wherein x is a real number greater than zero and Y is a real number greater than zero.