Rare earth element-doped multiple-core optical fiber and optical systems using the same

Abstract From the Canadian patent

A rare earth element-doped multiple-core optical fiber has a bundle of cores co-doped with Er and A1 primary cladding, layers covering each core and an outer cladding layer covering, all cores wherein one core is positioned substantially on a central axis of the outer cladding layer and surrounded by the remaining cores. The core diameter Dc of the center core is smaller than the core diameter Do of each peripheral core. The power of both signal light (1.53 µ m ~ 1.57 µ m wavelength bands) and pumping light (0.98 µ m or 1.48 ~ m band) propagating through the center core is reduced and the power propagating through each core is equalized, whereby flatter characteristics of gain to wavelength …