Abstract: Digital optical switches (1) with asymmetrical wave guides (2, 3; 5, 6) and an electro-optically controllable adiabatic coupling in a central region (4) must have a degree of crosstalk suppression of better than 20 dB for use in transparent optical networks. With X or Y arrangements, the invention provides for this purpose a grid device (10) in the central region (4) which affects the wave guide's inherent modes as the main cause of the crosstalk, i.e. amplitude and phase matching of the wave guide's inherent modes at the output. The result of the solution of the invention takes the form of a "cascade" of two different physical effects, each of which, of at least 20 dB, contributes to the overall result crosstalk suppression of better than 40 dB.