All-fiber ten-mode group erbium-doped amplifier for gain equalization with high gain

Area of Science:

• Optical Communications
• Fiber Optics
• Amplification Technologies

Background:

• High-capacity optical communication systems require amplification of multiple spatial modes.
• Existing amplifiers struggle with balanced gain across various modes, especially higher-order ones.
• Few-mode fiber amplifiers are crucial for advancing wavelength division multiplexing-mode division multiplexing (WDM-MDM).

Purpose of the Study:

• To construct and characterize an all-fiber ten-mode group amplifier.
• To achieve high gain and mode gain balance for 17 spatial modes.
• To evaluate amplification performance for WDM-MDM systems.

Main Methods:

• Fabrication of a few-mode erbium-doped fiber (FM-EDF) with a triple-ring-shaped core.
• Development of low-loss passive devices and a mode-selective excitation platform using a spatial light modulator (SLM).
• Investigation of gain characteristics under varying FM-EDF length, input signal power, and pump power.

Main Results:

• Achieved an average gain of 27.46 dB at 1550 nm with fundamental mode pumping (700 mW pump power).
• Demonstrated a minimum differential mode gain (DMG) as low as 3.13 dB.
• Obtained an average gain of 26.36 dB in the C-band with maximum DMG < 5 dB, amplifying 8 wavelength channels simultaneously.

Conclusions:

• The constructed 10-mode erbium-doped fiber amplifier (EDFA) exhibits excellent amplification performance.
• The amplifier provides high gain and good mode gain balance, suitable for complex mode signals including LP03.
• This EDFA holds significant practical value for future high-capacity WDM-MDM optical transmission systems.