Time-Bandwidth Product Perspective for Multi-Soliton Phase Modulation

TL;DR

This paper investigates the phase modulation of multi-soliton pulses in fiber optics, aiming to optimize their time-bandwidth product to improve spectral efficiency in nonlinear Fourier domain communication.

Contribution

It introduces numerical optimization of higher order soliton shapes to minimize their time-bandwidth product, providing analytical approximations and estimates for spectral efficiency improvements.

Findings

Optimized pulse shapes reduce the time-bandwidth product for second and third order solitons.

Analytical approximations describe the behavior of multi-soliton pulse duration and bandwidth.

Estimated minimal time-bandwidth product per eigenvalue informs potential spectral efficiency gains.

Abstract

Multi-soliton pulses are potential candidates for fiber optical transmission where the information is modulated and recovered in the so-called nonlinear Fourier domain. While this is an elegant technique to account for the channel nonlinearity, the obtained spectral efficiency, so far, is not competitive with classic Nyquist-based schemes. This is especially due to the observation that soliton pulses generally exhibit a large time-bandwidth product. We consider the phase modulation of spectral amplitudes of higher order solitons, taking into account their varying spectral and temporal behavior when propagating along the fiber. For second and third order solitons, we numerically optimize the pulse shapes to minimize the time-bandwidth product. We study the behavior of multi-soliton pulse duration and bandwidth and generally observe two corner cases where we approximate them analytically. We use these results to give an estimate on the minimal achievable time-bandwidth product per eigenvalue.