Modulational instability phase-matched by higher-order dispersion terms in dispersion-oscillating optical fibers

Abstract

The modulation instability (MI) process results from the interplay between linear and nonlinear effects. In fiber optics, it usually manifests itself by pumping in the anomalous dispersion regime and leads to the generation of two symmetric side-lobes around the pump. However it can also be observed when pumping in the normal dispersion region of uniform fibers as a phase-matching process involving higher-order dispersion (HOD) terms [1] or thanks to parametric resonance by longitudinally modulating the fiber dispersion [2,3]. In this work, we experimentally demonstrate that HOD phase-matching process also occurs in dispersion-oscillating fibers and that it leads to the generation of new MI frequencies. Their location can be estimated from the following quasi-phase matching relation: β2Ωq2 +(1/12) β4Ωq4 + 2γP = q(2π/Z) (1), where β2 and β4 are the second and fourth-order dispersion coefficients respectively, P is the pump power, γ is the nonlinear coefficient, Z is the modulation period and q is a positive or negative integer (q=0 corresponds to the conventional MI).