Gain equalization for a few-mode erbium-doped fiber amplifier supporting eight spatial modes

Area of Science:

• Optical Engineering
• Telecommunications

Background:

• Few-mode fiber amplifiers (FM-EDFAs) are crucial for increasing optical communication capacity.
• Achieving uniform modal gain in FM-EDFAs is a significant challenge.

Purpose of the Study:

• To design and propose a trench-assisted ring few-mode erbium-doped fiber amplifier (FM-EDFA) supporting eight spatial modes.
• To achieve gain equalization for the FM-EDFA using particle swarm optimization (PSO).

Main Methods:

• Design of a trench-assisted ring FM-EDFA.
• Utilizing particle swarm optimization (PSO) to determine optimal doping radius and concentration.
• Simulating amplification of eight spatial modes with a single pump mode (LP01).

Main Results:

• Achieved an average modal gain of approximately 20 dB for eight spatial modes.
• Demonstrated differential modal gain (DMG) less than 0.3 dB at 1550 nm.
• Showcased modal gain >20 dB and DMG <1 dB under gain competition with six wavelength signals.

Conclusions:

• The proposed FM-EDFA design offers excellent gain equalization and high average modal gain.
• The design exhibits good fabrication tolerance, with a refractive index fluctuation resulting in only a 0.77 dB DMG.
• This work contributes a robust FM-EDFA design for advanced optical communication systems.