Spatial Multiplexing in Fiber Optics: The 10X Scaling of Metro/Core Capacities

Optical networks have economically enabled an unabated exponential traffic growth over the past decades, with commercial wavelength-division multiplexed (WDM) systems carrying over 20 Tb/s of traffic per fiber, closely approaching the nonlinear Shannon limit. Looking at all physical dimensions available for further capacity scaling, it becomes clear that tapping into the spatial dimension is the only long-term scalable solution to overcome the looming optical network capacity crunch. As such, space-division multiplexing (SDM) is bound to become an important optical networking technology over the next decade. Integration of SDM components will be key in reducing cost, footprint, and energy consumption, while integration-induced crosstalk may be compensated through the use of digital signal processing similar to that of vectoring used in digital subscriber lines (DSL) or multiple-input-multiple-output (MIMO) techniques used in long-term evolution (LTE) wireless systems.