Back-to-Back Performance of the Full Spectrum Nonlinear Fourier Transform and Its Inverse

Abstract

In this paper, data-transmission using the nonlinear Fourier transform for jointly modulated discrete and continuous spectra is investigated. A recent method for purely discrete eigenvalue removal at the detector is extended to signals with additional continuous spectral support. At first, the eigenvalues are sequentially detected and removed from the jointly modulated received signal. After each successful removal, the time-support of the resulting signal for the next iteration can be narrowed, until all eigenvalues are removed. The resulting truncated signal, ideally containing only continuous spectral components, is then recovered by a standard NFT algorithm. Numerical simulations without a fiber channel show that, for jointly modulated discrete and continuous spectra, the mean-squared error between transmitted and received eigenvalues can be reduced using the eigenvalue removal approach, when compared to state-of-the-art detection methods. Additionally, the computational complexity for detection of both spectral components can be decreased when, by the choice of the modulated eigenvalues, the time-support after each removal step can be reduced. Numerical simulations are also carried out for transmission over a Raman-amplified, lossy SSMF channel. The mutual information is approximated and the eigenvalue removal method is shown to result in achievable rate improvements.

Shortening Solitons for Fiber-Optic Transmission

“…In most designs, either the solitonic part or the dispersive part of the NFT is used exclusively. There are a few works in which small numbers of solitons are added to a dispersive part [6]- [9], but the amount of energy in the solitonic part is small. Interestingly, one can observe a different picture when the NFT of conventionally modulated signals is taken.…”