Rare earth element doped multiple core optic fibre

摘要

A rare earth element-doped multiple-core optical fiber 31 has a bundle of cores 32-1 32-7 doped with Er and optionally Al, primary cladding layers 33 covering each core, and an outer cladding layer 34 covering all cores 32-1 32-7, wherein one core 32-1 being positioned substantially on a central axis of the outer cladding layer and surrounded by other six cores 32-2 32-7. A core diameter Dc of the center core 32-1 is smaller than a core diameter Do of each peripheral core 32-2 32-7. The power of both signal light (1.53 ~m 1.57 ~m wavelength bands) and pumping light (0.98 ~m or 1.48 ~m band) propagating through the center core 32-1 becomes lower and the power propagating through each core 32-1 32-7 is equalized, and the flatter characteristics of gain to wavelength are obtained. The surrounding cores may have higher refractive index or a larger amount of rare earth element. The fibre may be used as an amplifier.