Gain-equalized L-band few-mode erbium-doped fiber amplifier based on extremely simple fiber design

We numerically and experimentally demonstrated a low different modal gain (DMG) 4-LP modes L-band few-mode fiber amplifier by using an extremely simple fiber structure. The optimization effect of FM-EDF core radius on DMG performance and gain was numerically studied. An FM-EDF was fabricated by modified chemical vapor deposition (MCVD), for which the NA was improved to 0.25 and the core radius was properly selected to 8.1 μm. In the case of core pumping of the LP₁₁ mode at 1480 nm, an e DMG of ~0.7 dB and the gain of <17 dB was obtained for all four modes at 1570 nm. The results suggested that our proposed erbium-doped fiber amplifier has great potential for large-capacity long-haul mode division multiplexing (MDM) transmission system.