OPTICAL FIBER FOR OPTICAL ATTENUATOR HAVING FLAT ATTENUATION GAIN

PURPOSE: An optical fiber for an optical attenuator having a flat attenuation gain is provided, which has a flat attenuation characteristics at an optical signal band by doping a pair of metal ions having light absorption yields of a negative slope and a positive slope into a core of the optical fiber. CONSTITUTION: An optical fiber comprises a cladding layer(12) and a core layer(13). At least more than one component among the first metal ions of Fe, Cr and Mn, whose light absorption characteristics is decreased in a fixed wavelength band, and the second metal ion of a Cobalt(Co) component, whose light absorption characteristics is increased in the fixed wavelength band, are co-doped to the core layer. The second metal ion is formed by mixing a Ni component to the Co component. And an Al component also is co-doped to the core layer.