Modulation over Nonlinear Spectrum: Continuous and Discrete Spectrum

Nonlinear Frequency Division Multiplexing (NFDM) is considered when data is modulated in both parts of nonlinear Fourier spectrum: continuous spectrum and discrete spectrum. Multiplexing and demultiplexing of both spectra are explained and a time-domain detection method of discrete spectrum is introduced. The transmission of NFDM symbols is experimentally demonstrated over 1460 KM single-mode fiber with EDFA compensation. In each NFDM symbol, the continuous spectrum is modulated by 64 $times$ 0.5Gbaud 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 the gross rate of 55.3 Gbps. 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.