Patent ID: 6580549
Filing Date: 2003-06-17
Classification: H04B,H04J

Abstract:
A wavelength-multiplexed light amplifying apparatus comprising:a plurality of wavelength-multiplexed light amplifying units each including: a first wavelength-multiplexed light amplifying basic unit composed of an optical branching section having two input ports and two output ports for receiving a wavelength-multiplexed optical signal, which has a plurality of wavelengths, through a signal input port forming one of said two input ports to output said wavelength-multiplexed optical signal through said two output ports and optical amplifying sections respectively connected to said two output ports of said optical branching section; a second wavelength-multiplexed light amplifying basic unit having the same configuration as that of said first wavelength-multiplexed light amplifying basic unit and having a signal input port whose input side is connected to an output side of one optical amplifying section of said first wavelength-multiplexed light amplifying basic unit; and a third wavelength-multiplexed light amplifying basic unit having the same configuration as that of said first wavelength-multiplexed light amplifying basic unit and having a signal input port whose input side is connected to an output side of the other optical amplifying section of said first wavelength-multiplexed light amplifying basic unit, with said wavelength-multiplexed light amplifying units being connected in a multistage fashion in a manner that said signal input port of said optical branching section in said first wavelength-multiplexed light amplifying basic unit is connected to an output side of said optical amplifying section of one of said second wavelength-multiplexed light amplifying basic unit and said third wavelength-multiplexed light amplifying basic unit in said preceding wavelength-multiplexed light amplifying unit; a fourth wavelength-multiplexed light amplifying basic unit having the same configuration as that of said first wavelength-multiplexed light amplifying basic unit and having one optical amplifying section whose output side is connected to said signal input port of said first wavelength-multiplexed light amplifying basic unit in the forefront unit of said plurality of wavelength-multiplexed light amplifying units arranged in said multistage fashion; an excitation light source; a multiplexing section for multiplexing an excitation light from said excitation light source and said wavelength-multiplexed optical signal together; a gain equalizer interposed between said multiplexing section and a signal input port of said fourth wavelength multiplexed light amplifying basic unit; an output monitoring unit to monitor a filtered light of an output of a rearmost unit of said plurality of said wavelength-multiplexed light amplifying basic unit; and a gain control unit to control gains of said plurality of wavelength-multiplexed light amplifying units, arranged in said multistage fashion, on the basis of at least an output of the output monitoring unit.