Nonlinear codes for fiber-optic communication systems

We consider a nonlinear dispersive single-mode fiber as a communication channel in the normal dispersion regime. We simulate the propagation of binary sequences using OOK return-to-zero modulation at a bit rate of 10 Gb/s, under different dispersion and input power conditions. We measure the Euclidian distances among all received sequences in order to map the impact that dispersion and nonlinearity have on them. Treating each of these Euclidian distance maps as edges and the sequences as nodes in a graph, we find subsets of sequences that form nonlinear codes matched to this nonlinear channel, resulting in significant bit error rate improvement.