Anopticallyactivatedopticalswitchbasedonsuppressionofmodeinterference(SMI)ispresented.Theimagingpropertiesofmulti-modeinterference(MMI)sectionintheswitchwithY-branchcanbemodifiedbyacontrollinglightinjection.Theswitchwassimulatedbyfinitedifferencebeampropagationmethod(FD-BPM)andfabricatedonGaAlAs/GaAsepitaxialmaterials.Atthewavelengthof1.31μm,theprimaryexperimentshowedanextinctionratioofabout8dBwithcontrollinglightpowerdensityof73.5W/mm2.