In this paper, for the first time, the performance of an electro-optical router, working at a wavelength of 1.55 µm and based on multimode interference effects together with the electro-optic effect of smectic A lowast liquid crystal, is theoretically and numerically discussed. The device comprises: a single-mode input optical channel waveguide, a bimodal active region with a liquid crystal over-layer, and an output Y-branch to separate the two output channels. The active region is designed to allow a π shift between the two modes that it supports, by means of the electro-optic effect of smectic A lowast, in order to steer light from one output channel to the other. The principal advantages of such a device include a fast tuning speed, low power consumption, low cost and small device size.