文件类型：PDF文档
文件大小：642K
An optical fiber includes a rare-earth element-added core for serving as a gain medium, and a cladding formed on a periphery of the core. Pump light propagated through the cladding is coupled into the core. The cladding is in an undulation shape in the longitudinal direction of the cladding. The undulation shape of the cladding is formed according to a grating period at which the pump light is totally reflected and propagated in the cladding. The core includes an undulation shape in a longitudinal direction of the core. The cladding includes an undulating inner cladding, and an outer cladding provided on a periphery of the inner cladding. The core and/or the cladding is circular or abnormally circular in its transverse cross section.