138 Tbit/s Mode- and Wavelength Multiplexed Transmission over 6-Mode Graded-Index Fiber

We report on the multiplexing of 12 spatial channels and 120 wavelength channels in the C-band, each carrying 16-QAM symbols at 30 Gbaud over graded-index few-mode fiber. A combination of multiple fiber spools with positive and negative modal dispersion values are exploited to form a 59 km link with 0.35 ns differential mode group delay. The link is placed inside a 6-fold synchronized recirculating loop transmission setup. Photonic lanterns with low insertion and mode dependent loss are employed to excite the 6 spatial modes in the few-mode fiber. A net transmission rate of 138 Tbit/s at a spectral efficiency of 34.91 bit/s/Hz over 590 km is demonstrated.