Power dependence effects on the modulational instability spectra for highly birefringent fibers

Abstract

Modulational instability commonly refers to a non-degenerate stimulated four-wave mixing (FWM) interaction where phase matching is achieved through compensation of chromatic dispersion by self-phase modulation (SPM)[1]. In highly birefringent libers, phase matching of the FWM process responsible for MI does not require nonlinear dependence of the wavevectors contrary to single-mode or scalar MI. Apart from the analysis of Ref.[2] where a slight nonlinear dependence of the sideband frequencies was observed, in most previous experimental works on FWM processes in highly birefringent fibers, power dependent phase-matching effects were not evidenced[3,4]. The main reason for this is that the critical power level is well beyond any practical power levels, for operating conditions where the two pump waves copropagate with the same frequency. Quite to the contrary, when the two pump waves propagate with different frequencies, one can approach the critical power by just changing the frequency separation between the two pump waves, and thus observe power dependence effects.