Patent ID: 7751119

Claim:
An optical surge suppressive type optical amplifier comprising; a plurality of optical amplifying means each including an optical amplifying medium doped with at least rare-earth ions and a pumping section that supplies a pumping light to said optical amplifying medium, for amplifying a wavelength division multiplexed light input thereto by the stimulated emission of the rare-earth ions pumped by the pumping light from said pumping section, and said respective optical amplifying means being connected in series, wherein said optical amplifying medium the optical amplifying means arranged on the signal light output side among said plurality of optical amplifying means, is doped with the rare-earth ions substantially in uniform in high concentration within a predetermined region, and has a structure capable of causing a phenomenon in which the gain efficiency degradation is increased as a gain becomes larger, said optical amplifying means arranged on the signal light output side is configured to suppress an optical surge by the degradation of gain efficiency utilizing said phenomenon which is caused when the power of the input wavelength division multiplexed light is decreased.