OPTICAL FIBER AND FIBER TYPE DIFFRACTION GRATING

摘要

PROBLEM TO BE SOLVED: To make it possible to form fiber type diffraction gratings having sufficiently high reflectivity by irradiation with UV light. SOLUTION: This optical fiber has a core 100 which consists of quartz glass added with germanium oxide and has a first refractive index and first outside diameter and a clad 210 which is formed around this core 100 in tight contact with the core 100, has a second outside diameter of the diameter >=3 times larger than the first outside diameter, consists of the quartz glass added with the germanium oxide and has a first region having the refractive index distribution of the refractive index not decreasing in the diametral direction and increasing in at least a part. Such optical fiber is irradiated with the interference fringes of the UV light from the side face, by which the diffraction gratings by a change in the refractive index having the fringe intervals of the interference fringes as periods are formed in the core 100 within the irradiated regions and the first region of the clad 210.