Patent ID: 7031052

Claim:
An optical fiber amplifier, comprising: a pumping light LD (laser diode) for outputting pumping light; an EDF (erbium-doped fiber) having a first and a second input; a splitting coupler for receiving said pumping light and splitting said pumping light at a designated ratio to produce a first and a second output; a short wavelength transmitting coupler for receiving said first output and for directing inputted signal light and said first output to said first input of said EDF; a narrow-band coupler for receiving and filtering said second output and for directing said filtered second output to said second input of said EDF; said EDF receiving said inputted signal light, said first output, and said filtered second output; said EDF amplifying said inputted signal light using said first output and said filtered second output to produce amplified signal light; and said narrow-band coupler directing said amplified signal light away from said EDF; wherein: said short wavelength transmitting coupler has a passband; said narrow-band coupler has a passband; and said passband of said narrow-band coupler spans only a portion of said passband of said short wavelength transmitting coupler.