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One step closer to calculating the capacity of fibre-optic communication systems

26 October, 2016

We have established, for the first time, how to approach the capacity and spectral efficiency of optical systems when using nonlinear Fourier transform (NFT) methods in optical communication systems.  

Simultaneously, the study and derived results can be used for further spectral efficiency optimisations, in terms of system design. This means that higher information rates could be achieved over existing bandwidths in optical fibre systems.

Public, business and government activites rely on optical fibre infrastrucutre for e-commerce, streaming media, tele-presence and high performance distributed computing. Improving the efficiency of this infrastructure will improve the cost and energy per bit in communication systems. As such, the life of the existing infrastructure could be extended, even as demand for data is ever-increasing. 

So what is the maximum rate at which information can be transmitted error-free in fibre–optic communication systems?

In a paper published in the prestigious journal, Nature Communications, UNLOC members from Aston University, with colleagues from Ben Gurion University of the Negev (Beer Sheba, Israel) have demonstrated that using the specific mathematical properties of the nonlinear channel model and the so-called nonlinear Fourier transform, the lower bound of the capacity per symbol can be estimated as 10.7 bits per symbol with 500 GHz bandwidth over 2,000 km.

This work contributes to the paradigm shift required to master nonlinear (fibre-optic) chanels - away from current techniques originally developed for linear communication systems such as copper networks.

UNLOC Deputy Director, Prof Sergei Turitsyn said: “Transfer of bits/symbol into bits/sec is not straightforward yet in systems using NFT and is still a big challenge in this research area. However, our work sets a horizon for the communications industry to look to and beyond.”

UNLOC researcher and co-author of this work, Dr Yaroslav Prylepskiy, said: “The direct estimation of the information rate that can be transmitted over a given bandwidth, the spectral efficiency, is now possible when we have a particular system in hand.”

This work was published in the paper "Capacity estimates for optical transmission based on the nonlinear Fourier transform", Nature Communications 7, Article number: 12710 (2016).