Enhancing the Spectral Efficiency of Nonlinear Frequency Division Multiplexing Systems via Hermite-Gaussian Subcarriers

The nonlinear frequency division multiplexing (NFDM) is a promising concept in the field of optical fiber communications. Based on a well established mathematical technique of the nonlinear Fourier transform (NFT), a data modulation scheme has been suggested, which is intrinsically immune to Kerr nonlinearity and chromatic dispersion. However, most NFDM systems still suffer from low values of spectral efficiency due to the large burst sizes and the nonlinear interaction of the signal and the inline amplifier noise. Here, we show that this problem can be partially circumvented by using the Hermite-Gaussian spectral carriers. Using this approach, we are able to report a significantly higher spectral efficiency for NFDM schemes approaching 4.5 bits/s/Hz for a single polarization while keeping the bit error rate of uncoded input below the 7% hard decision forward error correction threshold.