L-band all-optical gain-clamped EDFA by utilizing C-band backward ASE

Gain-enhanced double-pass long-wavelength-band erbium-doped fiber amplifier using backward pumping

“…To improve the pump efficiency of the L-band as much as possible, several methods have been proposed, such as feedbacking unwanted amplified spontaneous emission ͑ASE͒ power into EDF to serve as the secondary pump through a circulator, 3,4 or incorporating a fiber Bragg grating, 5,6 C-band light assisted pumping, 7-10 and using a double-pass technique. 5,[11][12][13][14] Among these methods, the double-pass L-band EDFA is an efficient and cost-effective scheme, which uses a circulator or fiber loop mirror to recycle the L-band ASE into the EDF, again for the enhancement of the L-band gain. However, all the reported doublepass L-band EDFAs use the forward-pumped or dual-pumped 13,14 configuration, so the strong backward ASE power is output together with the amplified signals.…”

“…5,[11][12][13][14] Among these methods, the double-pass L-band EDFA is an efficient and cost-effective scheme, which uses a circulator or fiber loop mirror to recycle the L-band ASE into the EDF, again for the enhancement of the L-band gain. However, all the reported doublepass L-band EDFAs use the forward-pumped or dual-pumped 13,14 configuration, so the strong backward ASE power is output together with the amplified signals. This not only leads to the penalty of noise figure ͑NF͒, but also degrades the pump efficiency.…”