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Nonlinear signal multiplexing for communication beyond the Kerr nonlinearity limit


Current optical fibre transmission systems rely on modulation, coding and multiplexing techniques that were originally developed for linear communication channels. However, linear transmission techniques are not fully compatible with a transmission medium with a nonlinear response, which is the case for an optical fibre. As a consequence, the Kerr nonlinearity in fibre imposes a limit on the performance and the achievable transmission rate of the conventional optical fibre communication systems. Here we show that a transmission performance beyond the conventional Kerr nonlinearity limit can be achieved by encoding all the available degrees of freedom and nonlinearly multiplexing signals in the so-called nonlinear Fourier spectrum, which evolves linearly along the fibre link. This result strongly motivates a fundamental paradigm shift in modulation, coding and signal-processing techniques for optical fibre transmission technology.

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Figure 1: Illustration of the nonlinear spectrum and its evolution along a fibre link.
Figure 2: NFDM systems based on multiplexing signals in the nonlinear-spectrum domain.
Figure 3: Experimental set-up and performance of 64 × 0.5 GBd pre-compensated NFDM transmission.
Figure 4: Performance of fully modulated NFDM transmissions with the continuous part modulated by 64 overlapping sinc channels with 16 QAM, 32 QAM and 64 QAM formats and the discrete part modulated by two purely imaginary 8 PSK phase-modulated eigenvalues.


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Author information




S.T.L., V.A. and H.B. jointly discussed the general idea, planned the experiments and analysed the results. S.T.L. designed and detected the continuous spectrum. V.A. proposed the inverse NFT, and designed and detected the discrete spectrum. S.T.L. and H.B. performed the experiments. S.T.L. wrote the paper.

Corresponding author

Correspondence to Son Thai Le.

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The authors declare no competing financial interests.

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Le, S., Aref, V. & Buelow, H. Nonlinear signal multiplexing for communication beyond the Kerr nonlinearity limit. Nature Photon 11, 570–576 (2017).

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