Patent ID: 7466479

Claim:
An optical amplifier for amplifying WDM signals in a signal band of 1530 nm to 1600 nm, comprising a pump light source for generating a pump light in a wavelength of 1480 nm and an optical fiber, the optical fiber comprising: a core which comprises Al 2 O 3 -SiO 2 host glass and in which at least Er is included, a first cladding surrounding said core, the refractive index of which is smaller than said core, and a second cladding surrounding said first cladding, the refractive index of which is smaller than that of said core and greater than that of said first cladding, wherein the optical fiber has a cutoff wavelength of shorter than 1480 nm but larger than 1050 nm, the absorption coefficient of Er at 1530 nm of 12 dB/m or more, and the absolute value of the dispersion at 1580 nm of larger than 16 ps/nm/km.