Modulation Over Nonlinear Fourier Spectrum: Continuous and Discrete Spectrum

Nonlinear frequency division multiplexed (NFDM) systems are considered when data are modulated in both parts of the nonlinear Fourier spectrum: Continuous spectrum and discrete spectrum. An efficient algorithm is introduced to generate a time-domain signal from a given nonlinear spectrum. The transmission of such NFDM symbols is experimentally demonstrated over 1460 km standard single-mode fiber with EDFA-only amplification. In each NFDM symbol, the continuous spectrum is modulated by 64 x 0.5 Gbaud orthogonal frequency-division multiplexing (OFDM) symbols with 32-QAM format whereas the discrete spectrum contains four eigenvalues with the same imaginary part, each one is modulated by 8-PSK format, resulting a line rate of 55.3 Gb/s. The cross-talk between different nonlinear modes is quantified in terms of cross-correlation and the performance loss is computed in terms of mutual information when each nonlinear modes is detected individually.