A MgO/Ti bilaterally diffused optical waveguide is proposed. It features controlling the waveguide spot size and strengthening the optical confinement. It is experimentally shown that the coupling loss with single-mode fiber is reduced to 0.6 dB/facet. The bending loss is also suppressed from 2.2 dB of the Ti diffused waveguide to 0.2 dB at a 30-mm bending radius. The performance of the switch using this method is demonstrated. Total insertion loss is 2.6 dB. Driving voltage is 5.6 V with no degradation of the EO effect.