Managing Self-Phase Modulation in Pseudolinear Multimodal and Monomodal Systems

TL;DR

This paper introduces a semi-analytical model for managing self-phase modulation in dispersion-managed multimodal and monomodal fiber systems, demonstrating optimal dispersion for stable pulse bandwidth evolution through theoretical, numerical, and experimental validation.

Contribution

The paper presents a new semi-analytical model applicable to both multimodal and monomodal dispersion-managed fibers, enhancing understanding of bandwidth evolution and self-phase modulation effects.

Findings

Existence of an optimal chromatic dispersion for stable bandwidth evolution

Model accurately predicts bandwidth dynamics in multimodal fibers

Experimental results confirm theoretical and numerical predictions

Abstract

We propose a new semi-analytical model, describing the bandwidth evolution of pulses propagating in dispersion managed (DM) transmission systems using multimodal graded-index fibers (GRIN) with parabolic index. The model also applies to monomodal fiber DM systems, representing the limit case where beam self-imaging vanishes. The model is successfully compared with the direct integration of the (1+1)D nonlinear Schr\"odinger equation for parabolic GRIN fibers, and to experimental results performed by using the transmission of femtosecond pulses over a 5 m span of GRIN fiber. At the high pulse powers that are possible in multimodal fibers, the pulse bandwidth variations produced by the interplay of cumulated dispersion and self-phase modulation can become the most detrimental effect, if not properly managed. The analytical model, numerical and experimental results all point to the existence of an optimal amount of chromatic dispersion, that must be provided to the input pulse, for obtaining a periodic evolution of its bandwidth. Results are promising for the generation of spatio-temporal DM solitons in parabolic GRIN fibers, where the stable, periodic time-bandwidth behaviour that was already observed in monomodal systems is added to the characteristic spatial beam self-imaging.