A new L-band automatic-gain-controlled (AGC) erbium-doped fiber amplifier (EDFA) for dense wavelength-division-multiplexing transmission systems is presented, in which a single $1480\mathrm{nm}$ laser with an internal thermoelectric cooler is used as a primary pump for stable amplification. All C-band amplified spontaneous emission (ASE) is recycled by the secondary pump to enhance the gain efficiency. A fraction of the output signal is used as an electrical feedback monitor for the AGC to improve the gain-clamped (GC) flatness. Experimental results prove that the AGC EDFA has a gain flatness of better than $0.46\mathrm{dB}/40\mathrm{nm}$ , i.e., below 1.5%, and a higher gain of approximately $36.5\mathrm{dB}$ compared to that of approximately $35.3\mathrm{dB}$ for the conventional GC EDFA at $-30\mathrm{dBm}$ input signal power. The best gain flatness of $\pm 0.25\mathrm{dB}$ can be achieved over the dynamic range greater than $20\mathrm{dB}$ . The dynamic range of noise figure is between 6.7 and 7.1. The $3\mathrm{dB}$ down bandwidth is more than $40\mathrm{nm}$ . Overall dynamics measurements for the AGC EDFA feedback stabilization have been carried out. The recorded corresponding rise time of $1.565\mathrm{ms}$ indicates that the system does not exhibit any overshoot of gain or ASE variation due to the signal at the beginning of the pulse.