Abstract: New, compact optical--optical switches and/or wavelength converters manufacturable with good tolerances and evincing all or some of the following properties,compactnessgood ON/OFF switching ratiospossibility of cascading and bidirectional operationpolarization-independence feasibilityvery fast switchingare being developed.This requires developing components making use of different-order modes to mix the information signal and the control signal and to separate them. The compact Converter Combiner MMIs of the invention make possible:1. converting a first fundamental mode into first-order modes,2. superposing the first-order modes and the images of a second fundamental mode,3. the MMI operates simultaneously as mode splitter for the participating modes.Back-conversion of the generated modes of higher order into their initial modes also is possible.