Modulational instability in linearly coupled asymmetric dual-core fibers

Arjunan Govindarajan, Boris A. Malomed*, Arumugam Mahalingam, Ambikapathy Uthayakumar

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

We investigate modulational instability (MI) in asymmetric dual-core nonlinear directional couplers incorporating the effects of the differences in effective mode areas and group velocity dispersions, as well as phase- and group-velocity mismatches. Using coupled-mode equations for this system, we identify MI conditions from the linearization with respect to small perturbations. First, we compare the MI spectra of the asymmetric system and its symmetric counterpart in the case of the anomalous group-velocity dispersion (GVD). In particular, it is demonstrated that the increase of the inter-core linear-coupling coefficient leads to a reduction of the MI gain spectrum in the asymmetric coupler. The analysis is extended for the asymmetric system in the normal-GVD regime, where the coupling induces and controls the MI, as well as for the system with opposite GVD signs in the two cores. Following the analytical consideration of the MI, numerical simulations are carried out to explore nonlinear development of the MI, revealing the generation of periodic chains of localized peaks with growing amplitudes, which may transform into arrays of solitons.

Original languageEnglish
Article number645
JournalApplied Sciences (Switzerland)
Volume7
Issue number7
DOIs
StatePublished - 22 Jun 2017

Keywords

  • Asymmetric nonlinear fiber couplers
  • Coupled nonlinear Schrödinger equations
  • Linear stability approach
  • Modulational instability

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