Patent ID: 7046431

Claim:
A light amplifier interposed between an input side optical fiber and an output side optical fiber, comprising: a Raman excitation section for backwardly Raman-exciting said input side optical fiber; a first discrete light amplifier capable of carrying out a discrete amplification of light from said input side optical fiber and Raman-amplified by the exiting light from said Raman excitation section; a dispersion compensating fiber Raman amplifier capable of, while dispersion-compensating the light amplified by said first discrete light amplifier in a dispersion compensating fiber, Raman-amplifying the light propagating in said dispersion compensating fiber; and a second discrete light amplifier capable of carrying out a discrete amplification of the light from said dispersion compensating fiber Raman amplifier, wherein the level of light outputted from said second discrete light amplifier is set so that a first upper limit value set based on the amount of waveform deterioration caused by the nonlinear optical effect due to said output side optical fiber is not exceeded.