Patent ID: 6903865

Claim:
An optical communication system comprising: a) a signal source for providing a signal in an S-band of wavelengths; b) a fiber amplifier for amplifying said signal, said fiber amplifier having: 1) a core doped with Erbium and having a core cross-section and a refractive index n 0 ; 2) a depressed cladding surrounding said core, said depressed cladding having a depressed cladding cross-section and a refractive index n 1 ; 3) a secondary cladding surrounding said depressed cladding, said secondary cladding having a secondary cladding cross-section and a refractive index n 2 ; 4) a pump source for pumping Erbium contained in said core to a relative inversion D greater than about 0.7, such that said active material exhibits positive first gains in said S-band and second gains in a long wavelength band longer than said S-band, wherein said second gains are higher than said first gains; wherein said core cross-section, said depressed cladding cross-section, and said refractive indices n 0 , n 1 , and n 2 are selected to produce losses at least comparable to said second gains in said long wavelength band and losses substantially smaller than said first gains in said S-band.