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Phase-conjugated twin waves for communication beyond the Kerr nonlinearity limit


Kerr nonlinearity imposes a limit on the achievable transmission performance and capacity of optical fibre communication links. We show that the nonlinear distortions of a pair of phase-conjugated twin waves are essentially anticorrelated, so cancellation of signal-to-signal nonlinear interactions can be achieved by coherently superimposing the twin waves at the end of the transmission line. We demonstrate that by applying this approach to fibre communication, nonlinear distortions can be reduced by >8.5 dB. In dispersive nonlinear transmission, the nonlinearity cancellation additionally requires a dispersion-symmetry condition that can be satisfied by appropriately predispersing the signals. By using these techniques we succeed in transmitting a 400 Gb s−1 superchannel over 12,800 km of fibre. We further show a connection between the nonlinearity cancellation and a nonlinear noise squeezing effect. The concept of using phase-conjugated twin waves to suppress nonlinear interactions may prove beneficial in other physical systems governed by the nonlinear Schrödinger equation.

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Figure 1: Illustration of nonlinearity cancellation based on PCTWs and comparison with ML-PC.
Figure 2: Experimental observation of nonlinearity cancellation in non-dispersive transmission.
Figure 3: Experimental observation of nonlinearity cancellation in highly dispersive transmission.
Figure 4: Experimentally observed connection between nonlinearity cancellation and nonlinear noise squeezing.
Figure 5: Experimental verification of improved nonlinear tolerance to interchannel impairments.
Figure 6: Superchannel transmission with improved nonlinear transmission performance provided by PCTW.


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Authors and Affiliations



X.L., A.R.C., P.J.W. and R.W.T. jointly developed the concept. X.L. and S.C. designed and performed the experiment. X.L., A.R.C., P.J.W., R.W.T. and S.C. analysed the data. X.L. conducted the theoretical study and wrote the paper.

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Correspondence to Xiang Liu.

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Liu, X., Chraplyvy, A., Winzer, P. et al. Phase-conjugated twin waves for communication beyond the Kerr nonlinearity limit. Nature Photon 7, 560–568 (2013).

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