METHOD FOR PRODUCTION OF OPTICAL FIBER WITH GRANTING

摘要

PROBLEM TO BE SOLVED: To obtain an optical fiber with a grating by increasing a selected part by irradiation with converged pulse laser beam. SOLUTION: Pulse laser beam L1 of 370 to 600 nm in wavelength is transmitted through a phase mask 2 to obtain mask pattern light L2, an optical fiber F which has Ge-doped quartz glass as its core F1 and quartz-based glass as its clad F2 and is covered with an ultraviolet-ray setting type resin coating layer F3 is irradiated with the converged mask pattern light, and thus a refractive index variation part F4 corresponding to the intensity of diffracted light is formed in the core F1. The refractive index variation part F4 is arrayed along the axis of the optical fiber F in specific patter corresponding to the mask pattern light L2. As this optical fiber F, an optical fiber which is increased in sensitivity by a hydrogen or heavy hydrogen treatment or an optical fiber having a core doped with Ge to <=20 mol.% concentration is used. The optical fiber is irradiated with the pulse laser beam L1 preferably to 1×108 to 1×1012 W/cm2 power density.