Fig. 1. (a) Refractive index distribution of the FM-EDF. (b) Intensity profiles of LP₀₁ and LP₁₁ at 1550 nm and 980 nm.

Fig. 2. Gain variation of each guided mode with respect to the signal power when the pump modes are (a) LP₀₁ and (b) LP₁₁ modes, respectively.

Fig. 3. Experimental setup of the all-fiber FM-EDFA. TLS, tunable laser source; VOA, variable optical attenuator; PC, polarization controller; MSPL, mode-selective photonic lantern; ISO, isolator; WDM, wavelength division multiplexer; MSC, mode-selective coupler; OSA, optical spectrum analyzer.

Fig. 4. Near-field mode profiles of (a) the signal modes measured at points A, B, and C after amplification and (b) the pump modes at points C and D.

Fig. 5. Variations of the gains and the DMGs with respect to (a) LP₀₁ pump power and (b) LP₁₁ pump power when the input signal power is −10 dBm per mode.

Fig. 6. Variations of the gains and the DMGs over the C-band with (a) the LP₀₁ pumping scheme and (b) the LP₁₁ pumping scheme, when the pump power is 210 mW and the input signal power is −10 dBm per mode.

Fig. 7. Dynamic gain of the three guided modes as a function of the input signal power when the pump modes are (a) LP₀₁ and (b) LP₁₁, respectively, with the fixed pump power of 210 mW.