Modulational instability in dispersion-kicked optical fibers

TL;DR

This paper investigates modulational instability in dispersion-kicked optical fibers, deriving exact theoretical predictions for gain bands, and validates these findings through experiments with specially manufactured microstructured fibers.

Contribution

It provides the first exact analytical expression for MI gain bands in dispersion-kicked fibers and experimentally confirms the theory with custom fibers.

Findings

Theoretical gain band positions match experimental spectra.

Dispersion landscapes with Gaussian pulses approximate Dirac combs.

Experimental MI spectra agree well with numerical simulations.

Abstract

We study, both theoretically and experimentally, modulational instability in optical fibers that have a longitudinal evolution of their dispersion in the form of a Dirac delta comb. By means of Floquet theory, we obtain an exact expression for the position of the gain bands, and we provide simple analytical estimates of the gain and of the bandwidths of those sidebands. An experimental validation of those results has been realized in several microstructured fibers specifically manufactured for that purpose. The dispersion landscape of those fibers is a comb of Gaussian pulses having widths much shorter than the period, which therefore approximate the ideal Dirac comb. Experimental spontaneous MI spectra recorded under quasi continuous wave excitation are in good agreement with the theory and with numerical simulations based on the generalized nonlinear Schr\"odinger equation.