Nonlinear inverse synthesis for high spectral efficiency transmission in optical fibers

TL;DR

This paper introduces a nonlinear inverse synthesis method for optical fiber communication that encodes information onto nonlinear modes, enabling high spectral efficiency and reduced crosstalk, demonstrated with numerical simulations using advanced modulation formats.

Contribution

It presents a novel nonlinear inverse synthesis technique that allows direct encoding onto nonlinear spectral modes, improving spectral efficiency and crosstalk suppression in optical fiber transmission.

Findings

Achieves up to 4.5 dB performance improvement.

Compatible with various modulation formats.

Numerical validation of high spectral efficiency transmission.

Abstract

In linear communication channels, spectral components (modes) defined by the Fourier transform of the signal propagate without interactions with each other. In certain nonlinear channels, such as the one modelled by the classical nonlinear Schr\"odinger equation, there are nonlinear modes (nonlinear signal spectrum) that also propagate without interacting with each other and without corresponding nonlinear cross talk; effectively, in a linear manner. Here, we describe in a constructive way how to introduce such nonlinear modes for a given input signal. We investigate the performance of the nonlinear inverse synthesis (NIS) method, in which the information is encoded directly onto the continuous part of the nonlinear signal spectrum. This transmission technique, combined with the appropriate distributed Raman amplification, can provide an effective eigenvalue division multiplexing with high spectral efficiency, thanks to highly suppressed channel cross talk. The proposed NIS approach can be integrated with any modulation formats. Here, we demonstrate numerically the feasibility of merging the NIS technique in a burst mode with high spectral efficiency methods, such as orthogonal frequency division multiplexing and Nyquist pulse shaping with advanced modulation formats (e.g., QPSK, 16QAM, and 64QAM), showing a performance improvement up to 4.5 dB, which is comparable to results achievable with multi-step per span digital back propagation.