Exploring the scope of a mathematical tool to increase optical network capacity

23 February, 2017

UNLOC researchers have performed a mini-review surveying the current progress in the application of the so-called nonlinear Fourier transform - a powerful mathematical tool - to help expedite progress in this area of research.

 Researchers with the goal of unlocking optical network capacity understand that nonlinear effects in optical communication systems are a key limiting factor. Application of the nonlinear Fourier transform (NFT) has the potential to lead to vital nonlinearity mitigation tools for optical fibre channels and thus increase the capacity of broadband communications.

Such tools would help future-proof our fibre infrastructure against the ever-growing global demand for data, while actually keeping the existing “legacy” optical fibre systems.

UNLOC Deputy Director, Prof Sergei Turitsyn, led a team including many UNLOC researchers to conduct a survey of existing approaches involving the NFT and review the progress in this area with a focus on practical implications.

The basis of future technology to increase broadband capacity

The review highlights the current progress in the NFT-based optical transmission technology. Transmitting data using nonlinear Fourier modes (instead of conventional frequency bands) acts to strongly suppress the impact of nonlinear cross-talk within the data signal. This significantly mitigates the main source of capacity degradation.

The NFT therefore, could enable the development of critical new coding, modulation, transmission and processing techniques, inherently resilient to the nonlinearity. This would mitigate capacity degradation at high signal powers by eliminating cross-talk. It is, however not without its challenges.

Progress is limited by practical devices

Prof Turitsyn and his team suggest that one of the most significant challenges in the nascent NFT-based transmission technology is the limitations of practical devices. Currently available optical receivers, for example, do not have good enough resolutions to account for the profiles obtained via the NFT synthesis operation.

Another challenge is that computation of the NFT becomes increasingly difficult with higher signal power. It follows that research going forward should focus on improving algorithms as well as reducing their complexity in order to make the NFT a feasible option, both practically and economically.

This research is published in Optica: Sergei K. Turitsyn, Jaroslaw E. Prilepsky, Son Thai Le, Sander Wahls, Leonid L. Frumin, Morteza Kamalian, and Stanislav A. Derevyanko, "Nonlinear Fourier transform for optical data processing and transmission: advances and perspectives" Optica 4(3) 24, 307-322 (2017)