Patent ID: 8498045

Claim:
An optical amplifier comprising: a rare-earth doped optical fiber for receiving input light through one end and outputting output light through another end, the input light being input from an input port; an excitation light source for generating excitation light; an optical coupler for supplying the generated excitation light to the one end and/or the another end of the rare-earth doped optical fiber; and a reflector for reflecting an amplified spontaneous emission light out of a signal band traveling in opposite direction to the input light, the amplified spontaneous emission light being generated in the rare-earth doped optical fiber, wherein a wavelength of the input light is in a part of C-band, and the reflector reflects a light component of a part of a band in an amplified spontaneous emission, the part of the band being shorter-wavelength side than the wavelength of the input light.