Gain enhanced L-band Er3+-doped fiber amplifier utilizing unwanted backward ASE

A novel method of enhancing gain in the long wavelength band erbium-doped f iber amplifier is described using the unwanted amplified spontaneous emissi on (ASE) self-pumping technique. A dual-stage amplifier is deployed, where the unwanted backward ASE from the first stage is fully utilized to pump th e second stage amplifier. Gain improvement is observed that enables support for higher channel capacities in wavelength-division-multiplexed systems w ith negligible noise figure penalties. Flat-gain values in excess of 24 dB and noise figures < 5 dB are obtained from the proposed amplifier with a hi gher channel counts compared to the conventional amplifier.