We propose a new design of a 2x2 optical chip for switching optical modes based on silicon material. Input lights at fundamental mode of transverse electric (TE) polarization can be selected at the output by appropriately controlling a 180-degree butterfly-shaped phase shifter. The proposed device consists of two multimode interference waveguides MMI and a phase shifter packed in a compact size of 4.2μm x 0.22μm x 110.4μm. We use 3D-BPM numerical simulation method to evaluate optical conversion efficiency of device. The result shows that insertion loss is always less than 1.5dB and crosstalk is always below -30dB in a wavelength range from 1.5 to 1.6 . Moreover, we continue to evaluate the proposed device on the system with signal’s bitrate of 35Gbps, the bit error rate is always less than 10-10 in the whole bandwidth of 100nm
