Minimizing differential modal gain in cladding-pumped EDFAs supporting four and six mode groups

Abstract

We employ a Genetic Algorithm for the purpose of minimization of the maximum differential modal gain (DMG) over all the supported signal modes (at the same wavelength) of cladding-pumped four-mode and six-mode-group EDFAs. The optimal EDFA designs found through the algorithm provide less than 1 dB DMG across the C-band (1530-1565 nm) whilst achieving more than 20 dB gain per mode. We then analyze the sensitivity of the DMG to small variations from the optimal value of the erbium doping concentration and the structural parameters, and estimate the fabrication tolerance for reliable amplifier performance.

Amplification of 12 OAM States in an Air-Core EDF

“…As shown by the pink highlighted region in Fig. 2, the best pump family that provides the lowest DMGs (~ 0.25 dB) is OAM (8,1) . In comparison, the calculated DMG is about 3.1 dB when pumped by OAM (0,1) , because the OAM (0,1) pump has a much better overlap with the OAM (5,1) signal mode over the OAM (7,1) signal mode.…”

“…The vector fields of signal and pump modes are computed using COMSOL Multiphysics® software. In the cladding-pumped case, we treat the heavily multi-moded pump as a single transverse mode with uniform intensity across the inner cladding and annular guiding region [8]. Based on this, we adapt our vector-mode EDFA simulator to become cladding pump-able.…”

EDFA Design and Analysis for WDM Optical Systems Based on Modal Multiplexing

“…Specifically, in the particular case of few-mode (FM) systems, for an efficient WDM amplification, the EDFA must present high modal gain and low differential modal gain (DMG), as well as the usual requirement of equalized spectral gain (DSG) across the C-band. Because of its complexity, the design of FM-EDFAs than single-mode amplifiers and the design of FM-EDFAs for WDM signals has recently received major attention [5][6].…”

“…Alternatively, Kang et al proposed an annular doping profile with uniform FRIP and non-centered cladding pump for the equalization of 15 channels multiplexed in four group modes (LP 01,s , LP 11,s , LP 21,s and LP 02,s ) [8]. An optimization procedure concerning the doping profile, based on genetic algorithms, is adopted.…”

“…Although it presents good results, the optimization method used in [8] and [9] require a fairly timeconsuming numerical solution for the rate and propagation equations describing the behavior of the FM-EDFA. For WDM signals, the optimization procedure significant computational effort, since the necessary processing is much higher than that in the single channel case.…”