31 research outputs found
Regeneration limit of classical Shannon capacity
Since Shannon derived the seminal formula for the capacity of the additive linear white Gaussian noise channel, it has commonly been interpreted as the ultimate limit of error-free information transmission rate. However, the capacity above the corresponding linear channel limit can be achieved when noise is suppressed using nonlinear elements; that is, the regenerative function not available in linear systems. Regeneration is a fundamental concept that extends from biology to optical communications. All-optical regeneration of coherent signal has attracted particular attention. Surprisingly, the quantitative impact of regeneration on the Shannon capacity has remained unstudied. Here we propose a new method of designing regenerative transmission systems with capacity that is higher than the corresponding linear channel, and illustrate it by proposing application of the Fourier transform for efficient regeneration of multilevel multidimensional signals. The regenerative Shannon limit -the upper bound of regeneration efficiency -is derived
Space Division Multiplexing in Optical Fibres
Optical communications technology has made enormous and steady progress for
several decades, providing the key resource in our increasingly
information-driven society and economy. Much of this progress has been in
finding innovative ways to increase the data carrying capacity of a single
optical fibre. In this search, researchers have explored (and close to
maximally exploited) every available degree of freedom, and even commercial
systems now utilize multiplexing in time, wavelength, polarization, and phase
to speed more information through the fibre infrastructure. Conspicuously, one
potentially enormous source of improvement has however been left untapped in
these systems: fibres can easily support hundreds of spatial modes, but today's
commercial systems (single-mode or multi-mode) make no attempt to use these as
parallel channels for independent signals.Comment: to appear in Nature Photonic