| 摘要 |
PURPOSE: To obtain large gain by small pumping power in an optical amplifier, by a method wherein the amplifier has additive of phosphor nonuniformly distributed on the section of a core, and has larger concentration of the additive in the center of the core rather than on the boundary between the core and a clad. CONSTITUTION: A silica fiber has the following; a clad 11 formed of SiO2 wherein P2 O5 is added in order to decrease the fusion point and F is added in order to restrain increase of the refractive index, an outer core region 12 formed of SiO2 wherein GeO2 is added in order to increase the refractive index and P2 O5 is added in order to decrease the fusion point, and an inner core region 13 formed of SiO2 wherein Al2 O3 is added in order to increase the refractive index, P2 O5 is added in order to decrease the fusion point and prevent devitrification, and additive of phosphor is added in order to perform mutual action with pumping radiation. Most of the additives of phosphor contain rare earth metals. Important elements of them are Er which generates a laser light by three-level mechanism, and Nd which generates a laser light by threeand-four-level mechanism. The silica fiber is formed by using a modified chemical vapor deposition method which is usually called as MCVD. |
