Patent ID: 6954305

Claim:
An optical amplifier for amplifying signal light propagating in an amplification optical waveguide, comprising: a silica-based first amplification optical waveguide doped with Er, P, and Al in respective predetermined dopant amounts; a silica-based second amplification optical waveguide doped with Er in a predetermined dopant amount; and pumping light supplying means for supplying pumping light of a predetermined wavelength into each of said first amplification optical waveguide and said second amplification optical waveguide, wherein said first amplification optical waveguide and said second amplification optical waveguide are connected in series so that said first amplification optical waveguide is located upstream and said second amplification optical waveguide downstream in a propagating direction of said signal light, and wherein said first amplification optical waveguide and said second amplification optical waveguide amplify said signal light of a predetermined wavelength not less than the wavelength of 1570 nm, and wherein said second amplification optical waveguide is doped with Al in a predetermined dopant amount in addition to being doped with Er and is formed without being doped with P.