Optical amplifier, optical amplifying repeater and transmission apparatus of wavelength division multiplexed signal light using the same

Abstract

Flatness of a gain (optical output level) is maintained even when a wavelength division multiplex signal light (WDM signal light) is amplified in an optical amplification utilizing Raman amplification function. The optical amplifier comprises: two (first and second) pumping light sources for Raman amplification for outputting first and second pumping lights; the wavelength multiplexer 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 both pumping lights. A wavelength of the first pumping light is set such that the gain of the Raman amplified signal light declines in the right direction, and, on the other side, the wavelength of the second pumping light is set such that the gain declines in the left 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 each other.

1 . An optical amplifier, comprising: 
 a first pumping light source for Raman amplification, which outputs a first pumping light having a first wavelength;    a second pumping light source for Raman amplification, which outputs a second pumping light having a second wavelength; and    a wavelength multiplexer for Raman amplification, which allows said first and second pumping lights to be incident on an optical fiber transmission path where a signal light propagates, ‘wherein said signal light is Raman amplified in said optical fiber transmission path by said first and second pumping lights.    
   
   
       2 - 18 . (canceled)  
   
   
       19 . The optical amplifier  17 , comprising: 
 a first pumping light source for Raman amplification which outputs a first pumping light having a first wavelength    a second pumping light source for Raman amplification which outputs a second pumping light having a second wavelength; and    a wavelength multiplexer for Raman amplification, which allows said first and second pumping lights to be incident on an optical fiber transmission path where a signal light propagates.    wherein said signal light is Raman amplified in said optical fiber transmission path by said first and second pumping lights: and    wherein said signal light comprises a wavelength division multiplexed signal light (a WDM signal light), in which the signal lights having a plurality of wavelengths different from each other are wavelength division multiplexed:    an amplification medium for amplifying said signal light;    a third pumping light source for outputting a third pumping light to allow said amplification medium to be in an excited state;    a wavelength multiplexer for allowing said third pumping light to be incident on said amplification medium;    an optical splitter for splitting a part of said WDM signal light and outputting a split WDM signal light;    signal light extracting means for extracting two signal lights, which have the wavelengths different from each other, from each signal light included in said split WDM signal light;    an optical receiver for detecting the optical output level of each of the two signal lights extracted by said signal light extracting means; and    a pumping light output control circuit for controlling any one of the optical output levels and the wavelengths of said first and second pumping lights for Raman amplification according to the amount of difference between said two optical output levels;    wherein said optical splitter is arranged on a side to which said WDM signal light is output from said wavelength multiplexer for Raman amplification.    
   
   
       20 - 27 . (canceled)