Theoretical investigation of modulational instability in semiconductor doped dispersion decreasing fiber and its cutting edge over the existing fiber systems

Abstract

A theoretical study of modulational instability (MI) in the semiconductor doped dispersion decreasing fiber (SD-DDF) is presented. We consider the combination of saturation of nonlinear response and the dispersion decreasing fiber (DDF). The exact dispersion relation is calculated by means of linear stability analysis. Different fiber systems are considered alongside the proposed SD-DDF for insight and to offer the cutting edge of the proposed model over the others. The two extreme physical effects considered lead to an exciting outcome, where decreasing dispersion leads to broadening the spectral width and saturation, on the other hand, suppresses the MI gain and the bandwidth. A bandwidth relation between different fiber systems is presented, and the idea can open the design of a fiber structure with desired dispersion profile by a suitable manipulation of these effects. We propose that instead of using DDF whose bandwidth is limited by the manufacturing constraints, the use of SD-DDF offers better tailoring of the bandwidth profile by suitably altering the saturation parameter. Thus we emphasize that the proposed SD-DDF will be a feature prospect for wide range of applications, especially in the context of ultrashort pulse generation using MI.