Enhancing optical communications with brand-new fibers

Optical fibers have been considered to have effectively infinite capacity to cope with the rapid traffic increase in our information society, however as demand has grown and technology has been developed we have begun to realize that there is a fundamental limit to fiber capacity of ~ 100 Tbit/s per fiber for systems based on conventional single-core, single-mode optical fiber as the transmission medium. This limit arises from the interplay of a number of factors including the Shannon limit, optical fiber nonlinearities, the fiber fuse effect, as well as optical amplifier bandwidth. This article reviews the most recent research efforts around the globe launched over the past few years with a view to overcome these limitations and to substantially increase capacity by exploring the last degree of freedom available ­ namely the spatial domain. Central to this effort has been the development of brand-new fibers for space-division multiplexing (SDM) and modedivision multiplexing (MDM).