We theoretically investigate optimum configurations of 1480-pumped L-band (1570-1610 nm) gain-flattened erbiumdoped fiber amplifier (EDFA), using conventional erbium-doped fiber, for multi-wavelength wavelength division multiplexing (WDM) systems. The design criterion of L-band EDFA is to achieve the highest channel output power while keeping the differential channel output power to be ≤ 0.7 dB among 32 digital baseband channels with low channel noise figure of ≤ 5.5 dB. A total of nine L-band EDFA configurations are examined and compared. These configurations considered include the dual-forward, dual-backward, and different bi-directional pumping schemes, each with and without the midway optical isolator. Among all configurations, we find that the pump-passed case in forward-and-backward pumping scheme is the best amplifier configuration to offer the highest channel output power with good channel gain uniformity and moderate low noise figure. In addition, the tolerance of the ratio of first-staged EDF length to the total EDF length, and the effects of optical isolation of midway isolator, and pump power degradation on the characteristics of the best configuration are also examined. This investigation provides the EDFA configuration selection for multi-wavelength WDM L-band lightwave systems.