Design of Ring-Core Few-Mode-EDFA With the Enhanced Saturation Input Signal Power and Low Differential Modal Gain

We propose a design of ring-core few-mode fiber (RC-FMF) with the erbium doping at the cladding region near the outer ring edge. After the parameter optimization of the RC-FM-EDF, the intensity overlapping difference between LP
₀₁
and LP
₁₁
modes can be minimized, leading to a DMG of 0.22 dB for the corresponding ring-core few-mode erbium-doped fiber amplifier (RC-FM-EDFA). Meanwhile, in comparison with uniform core doping design, the saturation input signal power of the RC-FM-EDFA can be enhanced from -17.7 dBm and -16 dBm to -8.5 dBm for LP
₀₁
and LP
₁₁
modes, respectively. Consequently, our proposed RC-FM-EDFA is characterized by both low differential modal gain (DMG) and the enhanced saturation input signal power. Those new characteristics of the RC-FM-EDFA is ideally desired for future agile networks.