T. Nusantara, E. Soewono
A double-mode solution in an optical fiber is described, in the common approximation, by a coupled set of NLS equation, CNLS. This set is completely integrable only if the coefficients (dispersion, nonlinear and cross-phase) satisfy specific relations. Using a generalization of Hirota's formalism, we will show that coupled-soliton solutions can be found in the nonintegrable case. These coupled soliton solutions of CNLS correspond to "bound states" in the fiber. This boundedness is of a different character than the soliton collision described by the 2-soliton solution of a single NLS equation. Nevertheless, we show that there is remarkable agreement with the 2-soliton solution during interaction. We introduce the notion of "secondary modulation" to help the understanding of the phenomena.
Department of Mathematics, Center of Mathematics, Institut Teknologi, Bandung, Indonesia; Department of Mathematics, Universitas Negeri, Malang, Indonesia
