Optical transmission system and optical amplifying apparatus, optical amplifying unit, and optical coupler for the same

An optical amplifying apparatus used in an optical transmission system for transmitting a multiplexed optical signal belonging to two wavelength bands;

• said optical amplifying apparatus comprising:
• an optical branching section for separating said multiplexed optical signal into first and second wavelength bands different from each other and outputting thus separated multiplexed optical signals individually;
• two optical amplifiers, each having an amplification optical waveguide doped with a predetermined fluorescent material having a fluorescent spectrum peak in said first wavelength band, connected to two outputs of said optical branching section, respectively, for amplifying the each of the multiplexed optical signals;
• an optical combiner, connected to respective outputs of said optical amplifiers, for combining the amplified multiplexed optical signals and outputting thus combined optical signal;
• and
• an optical filter, connected between the optical amplifier for amplifying the multiplexed optical signal in said second wavelength band and said optical branching section, for blocking light in the vicinity of said fluorescent spectrum peak wavelength and transmitting therethrough light in said second wavelength band.

An optical amplifying unit used in an optical transmission system for transmitting a multiplexed optical signal belonging to two wavelength bands;

• said optical amplifier unit comprising:
• an optical amplifier, having an amplification optical waveguide doped with a predetermined fluorescent material, for amplifying a multiplexed optical signal in a wavelength band different from a wavelength band including a fluorescent spectrum peak of said fluorescent material;
• and
• an optical filter, connected to an input end of said optical amplifier, for blocking light in the vicinity of said fluorescent spectrum peak wavelength of said fluorescent material and transmitting therethrough light in the wavelength band to be amplified by said optical amplifier.

An optical coupler used in an optical transmission system for transmitting a multiplexed optical signal belonging to two wavelength bands;

• said optical coupler comprising:
• an optical branching section for separating said multiplexed optical signal into first and second wavelength bands different from each other and outputting thus separated multiplexed optical signals individually;
• and
• an optical filter, connected to an output end of said optical branching section for the optical signal in said second wavelength band, for guiding said optical signal to an optical amplifier having an optical amplification waveguide doped with a fluorescent material having a fluorescent spectrum peak in said first wavelength band, said optical filter blocking light in the vicinity of said fluorescent spectrum peak wavelength and transmitting therethrough light in said second wavelength band.