Excitation device for optical amplifier

A pumping device for optical amplifier for forward or backward pumping of a gain medium, comprising:

• a pump light generator configured to simultaneously output pump light with a single wavelength or a plurality of wavelengths from a plurality of output ports;
• a pump light multiplexer configured to polarization-multiplex or wavelength-multiplex the plurality of pieces of pump light which have been output from the plurality of the output ports of the pump light generator;
• a pump light superimposer configured, in the case of forward pumping, to multiplex the polarization-multiplexed or wavelength-multiplexed pump light and signal light and, in the case of backward pumping, to demultiplex the signal light from the signal light in which the polarization-multiplexed or wavelength-multiplexed pump light has been multiplexed;
• an optical waveguide for pump light configured to input the pump light which has been polarization-multiplexed or wavelength-multiplexed by the pump light multiplexer to the pump light superimposer;
• an optical waveguide for signal light configured, in the case of forward pumping, to input the signal light to the pump light superimposer and, in the case of backward pumping, to receive the signal light which has been demultiplexed by the pump light superimposer;
• a pump light output port configured, in the case of forward pumping, to superimpose the pump light on the signal light by outputting the pump light from the pump light superimposer to the gain medium so that the pump light propagates in the same direction as the signal light and, in the case of backward pumping, to superimpose the pump light on the signal light by outputting the pump light from the pump light superimposer to the gain medium so that the pump light propagates in an opposite direction to the signal light;
• and
• a polarization scrambler configured to collectively polarization-scramble the polarization-multiplexed or wavelength-multiplexed pump light which has been output from the pump light multiplexer and output the polarization-scrambled pump light to the optical waveguide for pump light.