Performance Analysis and Optimization Design of Gain Equalization and Gain Flattening in Few-Mode Erbium-Doped Fiber Amplifier

Yijie He; Wenqi Yu; Yihong Fang; Xiheng Huang; Yan Zeng; Ou Xu; Jianping Li

doi:10.3788/AOS250591

Acta Optica Sinica, Volume. 45, Issue 17, 1720024(2025)

Performance Analysis and Optimization Design of Gain Equalization and Gain Flattening in Few-Mode Erbium-Doped Fiber Amplifier

Yijie He^1,2,3, Wenqi Yu^1,2,3, Yihong Fang^1,2,3, Xiheng Huang^1,2,3, Yan Zeng^1,2,3, Ou Xu^1,2,3、*, and Jianping Li^1,2,3

Author Affiliations

¹Institute of Advanced Photonics Technology, School of Information Engineering, Guangdong University of Technology, Guangzhou 510006, Guangdong , China

²Key Laboratory of Photonic Technology for Integrated Sensing and Communication, Ministry of Education of China, Guangdong University of Technology, Guangzhou 510006, Guangdong , China

³Guangdong Provincial Key Laboratory of Information Photonics Technology, Guangdong University of Technology, Guangzhou 510006, Guangdong , China

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Figures & Tables(14)

Fig. 1. Simulation structure of FM-EDFA

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Fig. 2. Definitions of DMG, DWG, and ΔG

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$Schematic diagram of designed FM-EDF and mode-normalized light field intensity profile. (a) Refractive index distribution, mode light field distribution, and erbium ion doping concentration distribution of FM-EDF; (b) detailed erbium ion doping structure$

Fig. 3. Schematic diagram of designed FM-EDF and mode-normalized light field intensity profile. (a) Refractive index distribution, mode light field distribution, and erbium ion doping concentration distribution of FM-EDF; (b) detailed erbium ion doping structure

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Fig. 4. Wavelength gain flattening under different conditions. Impact of (a) LP₀₁ pump and (b) LP₁₁ pump on wavelength gain flattening when varying the doping radius $d_{1}$ ; impact of (c) LP₀₁ pump and (d) LP₁₁ pump on wavelength gain flattening when varying the doping concentration $ρ_{1}$

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Fig. 5. Wavelength gain flattening optimization using LP₁₁ pump. (a) Impact of varying $d_{1}$ and $ρ_{1}$ on η_DWG-AV of three signal modes; (b) signal mode gain spectra and DMG obtained under the optimal values of $d_{1}$ and $ρ_{1}$

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Fig. 6. Optimization results of modal gain equalization and wavelength gain flattening. (a) Influence of $d_{2}$ and $ρ_{2}$ on ΔG; (b) gain spectra and DMG under the optimal values of $d_{2}$ and $ρ_{2}$

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Fig. 7. Mode spectra of FM-EDFA. (a) Gain and DMG; (b) noise figure

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Fig. 8. Performance of FM-EDFA influenced by fiber length. (a) Gain and DMG; (b) DWG and ΔG

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Fig. 9. Performance of FM-EDFA influenced by pump power. (a) Gain and DMG; (b) DWG and ΔG

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Fig. 10. Performance of FM-EDFA influenced by signal input power. (a) Gain and DMG; (b) DWG and ΔG

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Fig. 11. Impact of simultaneous fluctuations in erbium doping concentration and radius. (a) Effect of variation rates in $ρ_{1}$ and $ρ_{2}$ from -10% to +10% on ΔG; (b) effect of variation rates in $d_{1}$ and $d_{2}$ from -10% to +10% on ΔG

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Fig. 12. Impact of parameter fluctuations in the erbium-doped region. (a) Effect of variation rates in $d_{1}$ and $ρ_{1}$ from -10% to +10% on ΔG; (b) effect of variation rates in $d_{2}$ and $ρ_{2}$ from -10% to +10% on ΔG

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Table 1. Designed FM-EDFA parameters
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Table 1. Designed FM-EDFA parameters
Parameter Value
$d_{1}$ 6.4 μm
$d_{2}$ 4.4 μm
$ρ_{1}$ $1.18 \times 10^{25} m^{- 3}$
$ρ_{2}$ $1.06 \times 10^{25} m^{- 3}$
Signal input power -10 dBm/mode
Forward pump power 400 mW （LP₁₁）
Fiber length 5 m

Table 2. Research result comparison of optimized DMG and DWG

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Table 2. Research result comparison of optimized DMG and DWG

Optimization schem	Ref.	Signal mode	Average gain /dB	Wavelengthrange /nm	DMG /dB	DWG /dB
Stitched long-period fiber grating	[13]	LP₀₁	-	1530‒1610	-	1.38
Fiber Bragg grating	[14]	LP₀₁	20.2	1570‒1610	-	0.88
Refractive index and Er doping distribution	[15]	LP₀₁	25	1525‒1565	-	2.6
Cascaded long-period fiber grating	[17]	LP₀₁, LP₁₁, LP₂₁,LP₀₂, LP₃₁, LP₁₂	17	1530‒1565	<0.6	<0.6
Optimizing pump mode and Erdoping distribution	This work	LP₀₁, LP₁₁, LP₂₁	24.1	1530‒1565	<0.14	<0.25

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Yijie He, Wenqi Yu, Yihong Fang, Xiheng Huang, Yan Zeng, Ou Xu, Jianping Li. Performance Analysis and Optimization Design of Gain Equalization and Gain Flattening in Few-Mode Erbium-Doped Fiber Amplifier[J]. Acta Optica Sinica, 2025, 45(17): 1720024

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