Differential modal gain optimization for weakly-coupled few-mode multi-core erbium-doped fiber amplifiers

Area of Science:

• Optical Communications
• Fiber Optics
• Amplifier Technology

Background:

• Space-division multiplexing (SDM) is crucial for increasing fiber optic capacity.
• Few-mode multi-core erbium-doped fiber amplifiers (FM-MC-EDFAs) are key components in SDM systems.
• Quantitative comparison of core vs. cladding pumping in FM-MC-EDFAs is lacking.

Purpose of the Study:

• To develop an accurate numerical model for cladding-pumped, weakly coupled FM-MC-EDFAs.
• To design and simulate three multi-core fiber (MCF) configurations for SDM.
• To quantitatively compare the performance of core pumping versus cladding pumping in these FM-MC-EDFAs.

Main Methods:

• Proposed a novel numerical model for cladding-pumped, weakly coupled FM-MC-EDFAs.
• Designed three distinct MCF configurations: single-mode 7-core, 2-mode 7-core, and 4-mode 7-core EDFs.
• Optimized the doping profile of the 4-mode fiber to minimize differential modal gain.

Main Results:

• Core pumping demonstrated superior power conversion efficiency (PCE) across all tested MCF designs (41.92% - 43.83%).
• Noise figure (NF) differences between core and cladding pumping were minimal (max 1.18 dB) when gain spectra were similar.
• Optimized doping profiles effectively reduced differential modal gain in the 4-mode fiber.

Conclusions:

• Core pumping is a more efficient method for FM-MC-EDFAs in terms of PCE.
• The choice between core and cladding pumping depends on specific performance requirements, particularly concerning NF and PCE.
• Findings offer practical guidance for optimizing SDM optical amplifier design.