Propagation of amplified spontaneous emission (ASE) in cladding-pumped long-wavelength-band erbium-doped fiber amplifiers (EDFAs) is analyzed numerically. Forward and backward ASE power dependence on cladding area is analyzed for both pumping directions. ASE power propagating counterdirectionally to the pump is found to experience strong dependence on the cladding area. Increasing the cladding area results in more uniform pump distribution along the EDF, preventing short-wavelength gain and ASE buildup. Quantum conversion efficiency in cladding-pumped L-band EDFAs is discussed.