ABSTRACT
A continuous wave with a cubic nonlinearity in an anomalous dispersion regime is known to develop instability with respect to small modulations in amplitude or in phase in the presence of noise or any other weak perturbation, called modulational instability (MI). MI is governed by the nonlinear Schrödinger equation, which inherently admits the formation of solitary pulses or envelope solitons as a result of the delicate balance between anomalous group velocity dispersion and self-focusing Kerr nonlinearity. Systems of coupled nonlinear Schrödinger (CNLS) equations have been demonstrated to be relevant in many scientific applications, especially in hydrodynamics and optics. The evolution of the optical beam in two twin-core fiber could be given by four linear CNLS equations. The periodic power transfer between the two cores of the fiber is governed by the linear coupling coefficient. Direct numerical simulations were run in order to understand the dynamics of CW states under MI in the nonlinear regime.
