Design and fabrication of an intrinsically gain flattened Erbium doped fiber amplifier

TL;DR

This paper presents the design and fabrication of an intrinsically gain flattened Erbium doped fiber amplifier using a dual-core fiber with tailored phase-resonant coupling, achieving uniform gain across the C-band without additional filtering.

Contribution

It introduces a novel dual-core fiber design that inherently flattens gain in EDFA, reducing reliance on external gain flattening filters.

Findings

Median gain of approximately 28 dB across the C-band

Gain variation within ±2.2 dB over the C-band

Effective for 16-channel standard signals at -20 dBm/channel

Abstract

We report design and subsequent fabrication of an intrinsically gain flattened Erbium doped fiber amplifier (EDFA) based on a highly asymmetrical and concentric dual-core fiber, inner core of which was only partially doped. Phase-resonant optical coupling between the two cores was so tailored through optimization of its refractive index profile parameters that the longer wavelengths within the C-band experience relatively higher amplification compared to the shorter wavelengths thereby reducing the difference in the well-known tilt in the gains between the shorter and longer wavelength regions. The fabricated EDFA exhibited a median gain ?28 dB (gain excursion below $\pm$2.2 dB within the C-band) when 16 simultaneous standard signal channels were launched by keeping the I/P level for each at ?20 dBm/ channel. Such EDFAs should be attractive for deployment in metro networks, where economics is a premium, because it would cut down the cost on gain flattening filter head.