Abstract:In this paper,the multimode waveguide lengths and the output port locations of a SOI(silicon on insulator)material-based 1x4 MMI(multimode interference)optical splitter are optimized by means of FD-BPM (finite difference-beam propaga-tion method).An improved 1x4 MMI optical splitter is designed.Compared with an usual optical splitter,a smaller loss O.12dB and a better output port power uniforrnity 0.11dB are achieved for the optical signal transmission.