Demonstration of an all-fiber cladding-pumped FM-EDFA with low differential modal gain

An all-fiber few mode erbium doped fiber amplifier (FM-EDFA) with low differential modal gain (DMG) is theoretically and experimentally demonstrated. Firstly, a double-cladding six-mode EDF (6M-EDF) with triple-layer erbium ion doping is designed and fabricated. Then, based on the homemade 6M-EDF, an all-fiber cladding-pumped FM-EDFA is implemented with high modal fidelity. Our experimental results show that the DMG is less than 2.65 dB in the wavelength range of 1535–1570 nm, the modal gains for the 6 modes are higher than 19 dB, and the noise figures are about 4.61–7.66 dB. The all-fiber FM-EDFA with low DMG offers a cost-effective and stable alternative for high-integrated all-fiber long-haul spatial division multiplexing applications.