Patent ID: 7876497

Claim:
A method for amplifying an optical signal in a long-band optical amplifier, the method comprising: propagating the optical signal in a first rare-earth-doped amplification waveguide; pumping said first rare-earth-doped amplification waveguide with a first part of amplified spontaneous emission to pre-amplify the optical signal propagating therein into a pre-amplified optical signal; propagating said pre-amplified optical signal in a second rare-earth-doped amplification waveguide; pumping said second rare-earth-doped amplification waveguide with a pump light source to amplify the pre-amplified optical signal propagating in the pumped second rare-earth-doped amplification waveguide into an amplified optical signal, said pumping generating amplified spontaneous emission in said second rare-earth-doped amplification waveguide; splitting said amplified spontaneous emission in at least said first part and a second part of amplified spontaneous emission; coupling said first part into said first rare-earth-doped amplification waveguide for said pumping said first rare-earth-doped amplification waveguide to pre-amplify the optical signal propagating therein; and coupling said amplified optical signal and said second part in a third rare-earth-doped amplification waveguide, said second part pumping said third rare-earth-doped amplification waveguide for post-amplification of said amplified optical signal.