An optical amplifier for amplifying WDM light which includes an optical fiber
used as an optical amplification medium for amplifying WDM light. A pump light
source is provided to generate pump light and an optical splitter is provided to
generate first branch pump light and second branch pump light from the pump light.
The optical amplifier further includes an optical device guiding the first branch
pump light to the optical fiber and guiding the second branch pump light to a transmission
line connected to an input side of the optical amplifier.
