Optical amplifier, optical amplifying repeater and transmission apparatus for wavelength-division-multiplexed signal light

摘要

Flatness of a gain (optical output level) is maintained even when wavelength-division-multiplexed signal light (WDM signal light) is optically amplified utilizing a Raman amplification function. The optical amplifier comprises: two (first and second) pumping light sources for Raman amplification for outputting first and second pumping lights; wavelength multiplexers for Raman amplification for allowing the first and second pumping lights to be incident on optical fiber transmission paths, where the WDM signal light propagates, in the direction opposite to the propagation direction of the signal light. The signal lights are Raman-amplified by the pumping lights. A wavelength of the first pumping light is set such that the gain of the Raman-amplified signal light declines in one direction, and, on the other side, the wavelength of the second pumping light is set such that the gain declines in the other direction. Gradients for showing a relation between the wavelength and the gain in Raman amplification by the first and second pumping lights are made to be in opposite directions from each other. Optical output levels and the wavelengths of the first and second pumping lights are set such that the gains for the signal lights included in the Raman-amplified WDM signal light become substantially equal to one another.