Patent ID: 8537458

Claim:
An optical fiber amplifier, comprising: an optical fiber for optical amplification, including: a core portion doped with at least erbium and aluminum, a cladding portion formed around the core portion and having a refractive index smaller than that of the core portion, a peak value of absorption coefficient of 35 dB/m or greater at a wavelength around 1530 nanometers, normal dispersion characteristics and an effective core area of 20 square micrometers or larger, at a wavelength of 1550 nanometers, and a power conversion efficiency of a conversion from pumping light to amplified light having a wavelength of 1550 nanometers being 30% or more; a pumping light source configured to output the pumping light for pumping the optical fiber for optical amplification; and at least one connection optical fiber connected to the optical fiber for optical amplification and configured to guide light being amplified or the amplified light, wherein at the wavelength of 1,550 nanometers, a sum of a product of a wavelength dispersion value and a length of the optical fiber for optical amplification and a product of a wavelength dispersion value and a length of the at least one connection optical fiber is approximately zero.