Search for: [Abstrakt = "In this paper, we calculate three effective refractive indexes for cascaded silicon\-on\-insulator \(SOI\) nonlinear directional coupler. For each effective refractive index, the coupling length LC, core\-to\-distance\-ratio K and switching threshold power Pi, m are calculated, respectively. However, there are some fabrication errors, which are ΔW, ΔH, ΔK in the height of Si layer and width of Si layer and error of core\-to\-distance\-ratio. We have analyzed the influence of power transmission efficiency Ti, j and relative transmission efficiency error Δi, j caused by the change of ΔW, ΔH, ΔK. Furthermore, we find the tolerance range of ΔW, ΔH, ΔK for Ti, j and Δi, j in couplers a, b, c. The other four input pulses with different powers are switched to four different ports. Although output pulses show some little compression and loss, the value of η is very small and output pulse waveforms are not affected seriously. The basic switching function has been realized, so this design is proved to be effective."]