C + L Band Distributed Few-mode Raman Amplification with Flattened Gain for Mode-division-multiplexed Optical Transmission over 75-km Few-mode Fiber

We first experimentally demonstrate a C + L band few-mode Raman amplifier with 4-dB flat on-off gain. In the 1530-1605 nm range, the wavelength dependent gain for both LP01 and LP11 modes is less than 0.6-dB. The amplifier was successfully employed in MDM transmission.