A switch based on an acousto-optic Bragg cell for telecommunications applications was developed. Two Bragg gratings are superimposed in the same crystal by applying two RF signals simultaneously to the cell. This results in the appearance of spurious optical beams. All the unwanted beam characteristics have been evaluated to optimize the performances of this device. The measurements have been made using an optical heterodyne detection method. The cell is made with a planar phased array transducer with a crystal.