Communication system using s-band er-doped fiber amplifiers with depressed cladding

Abstract

An optical communication system such as a Wavelength-Division-Multiplexed (WDM) or Dense Wavelength-Division-Multiplexed (DWDM) communication system using Erbium doped fiber amplifiers (EDFAs) for amplifying signals in the S-band. The fiber amplifier has a core doped with Erbium and defined by a core cross-section and a refractive index n. The fiber amplifier has a depressed cladding surrounding the core and a secondary cladding surrounding the depressed cladding. The depressed cladding has a depressed cladding cross-section and a refractive index n, and the secondary cladding has a secondary cladding cross-section and a refractive index n. The fiber amplifier has a pump source for pumping the Erbium to a level of high relative inversion D such that the Erbium exhibits positive gains in the S-band and high gains in a long wavelength band longer than the S-band, i.e., in the C- and L-Bands. The core cross-section, the depressed cladding cross-section and the refractive indices n, n, and nare selected to obtain losses at least comparable to the high gains in the long wavelength band and losses substantially smaller than the positive gains in the S-band. The optical communication system can employ the fiber amplifier as a pre-amplifier, a power-boosting amplifier or an in-line amplifier.