LONG-PERIOD FIBER GRATING ELEMENT AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide a long-period fiber grating element having a stable characteristic, and to provide a manufacturing method thereof. SOLUTION: In this long-period fiber grating element 1, an optical fiber 10 mainly consisting of silica glass includes a core part 11 added with GeO2 and a clad part 12 around the core part 11. A grating 20 formed in the core part 11 has alternate high-refractive index parts 21 and low-refractive index parts 22, while a period of the refractive index modulation is a long period of about several hundredμm. Both or one of hydroxyl groups and water molecules are diffused and infiltrated into a surface vicinity 12A of the clad part 12 around the core part 11 formed with the grating 20. A total concentration of the hydroxyl group or water molecule diffused and infiltrated into the surface vicinity 12A of the clad part 12 is preferably above 100 ppm.