1.58-μm band gain-flattened erbium-doped fiber amplifiers for WDM transmission systems

This paper describes the amplification characteristics of gain-flattened Er/sup 3+/-doped fiber amplifiers (EDFAs) by using 0.98-/spl mu/m and 1.48-/spl mu/m band pumping for a 1.58-/spl mu/m band WDM signal. Silica-based Er/sup 3+/-doped fiber (S-EDF) and fluoride-based Er/sup 3+/-doped fiber (F-EDF) have gain-flattened wavelength ranges from 1570 to 1600 nm and from 1565 to 1600 nm, respectively, and exhibit uniform gain characteristics with gain excursions of 0.7 and 1.0 dB, and the figure of merit of the gain flatness (gain excursion/average signal gain) of 3 and 4.3%, respectively, for an eight-channel signal in the 1.58-/spl mu/m band. We show that 1.48-/spl mu/m band pumping has a better quantum conversion efficiency and gain coefficient, and that 0.98-/spl mu/m band pumping is effective for improving the noise characteristics. We also show that the EDFAs consisting of two cascaded amplification units pumped in the 0.98-/spl mu/m and 1.48-/spl mu/m bands are effective in constructing low-noise and high-gain 1.58-/spl mu/m band amplifiers.