Chapter 6: Space-division multiplexing in multi-core and multi-mode fibers

Space is the only degree of freedom of the electromagnetic wave that is un- used in conventional fiber-optic communication systems, which makes spatial multiplexing the only viable approach to scale the capacity of future fiber-optic systems in response to the ever growing demand for data traffic. A special implementation of space-division mul- tiplexed (SDM) transmission, intensely researched worldwide over the past decade, is the one based on the use of multi-core and multi-mode fibers, where multiple spatial channels are integrated in a single fiber. This chapter reviews some of the work performed by the Italian optical communications community in this domain, in the framework of the CNIT National Laboratory of Advanced Optical Fibers for Photonics.