Amplifier having pump fiber filter

摘要

Disclosed is a fiber amplifier including a gain fiber and a source of pump power having a wavelength lambda p coupled to one end thereof. A signal of wavelength lambda s is introduced into a first end of the gain fiber, and an amplified signal of wavelength lambda s is coupled from the second end thereof. The signal can traverse an undesired secondary path as well as a preferred primary path to the amplifier output. To prevent light of wavelength lambda s from traversing the secondary path and thus increasing the amplifier noise figure, the amplifier includes attenuating fiber means for attenuating that portion of the signal of wavelength lambda s that propagates in the secondary path.