N-dark-dark solitons for the coupled higher-order nonlinear Schrodinger equations in optical fibers

In this paper, we construct the binary Darboux transformation on the coupled higherorder dispersive nonlinear Schrodinger equations in optical fibers. We present the N-fold iterative transformation in terms of the determinants. By the limit technique, we derive the N-dark-dark soliton solutions from the non-vanishing background. Based on the obtained solutions, we find that the collision mechanisms of dark vector solitons exhibit the standard elastic collisions in both two components.