To enhance the transparency of coupled-waveguide system

this paper analyze the influence of waveguide loss

nonlinearity and the modulation parameters on the system performance.In the approximation of weak-waveguide theory

the nonlinear Schr9 dinger equations are solved numerically by Runge-Kutta method and the results show that with the increase of the coupled-waveguide loss

the transparency of input waveguide will decrease firstly and then increase counter-intuitively.Further results indicate that the power distribution of input waveguide can be enhanced effectively by increasing the nonlinearity of input waveguide.In this way

the effect of transparency is enhanced.Our results are universal for ordinary coupled systems and periodic modulation systems.Therefore

the maximum value of transparency can be obtained through increasing the nonlinearity of input waveguide and coupled-waveguide loss while the input waveguide is modulated periodically with appropriate parameters.