An air-hole-assisted few-mode erbium-doped fiber (AH-FM-EDF) with a uniform erbium ion doping profile is proposed for gain equalization. By introducing the central air hole, the mode field distribution is strongly modified, contributing to a significant improvement in reducing the differential modal gain (DMG). Numerical results show that the gains of each mode can all reach 20 dB and the DMG is about 0.4 dB at 1550 nm in either core-pumping or cladding-pumping cases. Besides, the amplifier is well-behaved in gain-flattening with a noise figure (NF) of about 4.5 dB over the whole C-band. The proposed fiber shows much flexibility and robustness in gain equalization due to its simple uniform doping profile and pump-mode selection.
展开▼
