supported by the National Natural Science Foundation of China (No. 62171078);the National Key R&D Program of China (No. 2018YFB1801003)。
All-fiber few-mode erbium-doped fiber amplifiers(FM-EDFAs) with isolation and wavelength division multiplexers(IWDMs)have been developed to enable flexible pumping in different directions. The FM-EDFA can achieve >30 ...