Nonlinear Fourier transform (NFT) based transmission technique relies on the integrability of the nonlinear Schrodinger equation (NLSE). However, the lossless NLSE is not directly applicable for the description of light evolution in fibre links with lumped amplifications such as Erbium-doped fibre amplifier (EDFA) because of the non-uniform loss and gain evolution. In this case, the path-averaged model is usually applied as an approximation of the true NLSE model including the fibre loss. However, the inaccuracy of the lossless path-average model, even though being small, can also result in a notable performance degradation in NFT-based transmission systems. In this work, we extend the theoretical approach, which was firstly proposed for solitons in EDFA systems, to the case of NFT-based systems to constructively diminish the aforementioned performance penalty. Based on the quantitative analysis of distortions due to the use of path-average model, we optimise the signal launch and detection points to minimise the models mismatch. Without loss of generality, we demonstrate how the approach works for the NFT systems that use continuous NFT spectrum modulation (vanishing signals) and NFT main spectrum modulation (periodic signals). Through numerical modelling we quantify the corresponding improvements in system performance.
Bibliographical noteCopyright: The authors, 2017. This work is licensed under a Creative Commons Attribution 3.0 License. For more information, see http://creativecommons.org/licenses/by/3.0/
Funding: This work was supported in part by the U.K. EPSRC Programme under Grant UNLOC EP/J017582/1 and in part by the Russian Science Foundation under Grant 17-72-30006 (S.K.T.).
- Fibre-optic communication
- nonlinear Fourier transform
- nonlinear inverse synthesis
- periodic nonlinear Fourier transform
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