Multi-clad optical fiber design for ultra-wideband modulation instability

Abstract

Developments of electro-optic (EO) modulators do not have a satisfactory pace and bandwidth restrictions are still limited to several hundred GHz, thus, obtaining methods that enable using broadband optical channels are key factors in high-speed optical communications. In this paper, Modulation Instability (MI) as an approach in order to improve the performance of EO modulators, is investigated in the anomalous and zero-dispersion regimes of proposed optical fiber. In present conventional optical fibers, MI is observed over a few hundred gigahertz bandwidths at low pump power. In order to obtain ultra-wideband (a few Terahertz) bandwidths and maximum gain in the MI process at low pump power, a new structure for optical fiber is proposed. The genetic algorithm is utilized for performance optimization in optical fiber design. It is shown that the proposed optical fiber is able to support MI for a few Terahertz bands at low pump power (100mW). Furthermore, in this analysis, it is demonstrated that higher-order dispersion terms have a strong impact on modulation instability. Finally, it is concluded that the geometrical and optical parameters of optical fiber are key factors to control modulation instability parameters (gain and bandwidth). The proposed optical fiber can be used as an optical booster in order to compensate frequency response of EO modulators, which is a considerable step forward in high-speed optical communication.