Nonlinear codes for dispersive nonlinear fibers

We consider a single wavelength channel in a nonlinear dispersive single-mode fiber. We simulate the propagation of binary sequences using on-off keying return-to-zero modulation at a bit rate of 10 Gb/s, under different dispersion and input power conditions. We determine the impact that dispersion and nonlinearity have on the pulse sequences by measuring the Euclidian distances (EDs) among all pairs of received sequences. We then model the set of EDs as a fully connected graph and by means of a clique-finding algorithm we search for subsets of sequences that form codes matched to this nonlinear channel, resulting in significant bit-error-rate improvement.