ASE Suppression in Backward-Pumped Er/Yb Double-Cladding Fiber Amplifier via Cladding Feedback

We demonstrate a backward-pumped 1550 nm narrow-linewidth Erbium-Ytterbium double-cladding fiber amplifier with amplified spontaneous emission (ASE) suppression. Compared with the typical backward-pumped amplifier without feedback, the ASE power can be suppressed by over 2 dB by cladding feedback without other filters. The slope efficiency is 23.2%, which only decreased by 0.4%. The linewidth and relative intensity noise of 4.51 kHz and -92 dBm/Hz are also compared with those of the typical backward-pumped amplifier without feedback.