Optical MIMO-SDM: From interface rates and fiber capacity scaling to physical-layer security

Space-division multiplexing (SDM) is considered the only long-term viable path for sustained capacity scalability in optical networks, from metropolitan Mega-Datacenter interconnects all the way to ultra-long-haul transport systems. To counteract crosstalk arising from dense photonic integration, multiple-input multiple-output (MIMO) techniques are likely to be used, following techniques that both wireless and copper access systems have implemented over the past two decades. In addition to cost-effective capacity scaling, MIMO-SDM also promises a significant amount of inherent physical-layer security.