Optical communication system

摘要

This method comprises the steps of: introducing light signals having different wavelengths into an optical amplifier, wherein the optical amplifier has a plurality of fibers with rare earth element doped therein and P is selectively doped in said fibers; and introducing excitation light into the fibers, the excitation light being able to excite the rare earth element. At least one of the fibers has Al therein and the relationship between the Al and P concentration satisfies following expression: C(P) / C(Al) > 2, where, C(P) is P concentration in the fiber, and C(Al) is Al concentration in the fiber.