Energy-efficient optical transport capacity scaling through spatial multiplexing

We discuss the role of parallel transport options, such as spatial multiplexing or multi-band transmission, in the capacity scaling of optical transport systems. Taking current experimental spectral efficiency records as a baseline, a system supporting 20 b/s/Hz over 1,500 km can be about 100 times more energy efficient when it is built using spatial multiplexing than when it is built using a single waveguide at high capacity.