We present a method to implement an $M{ imes}N$ switching system by use of an $M{ imes}1$ multimode planar waveguide and N hologram filters. The $M{ imes}1$ multimode planar waveguide provides the pass of optical signals and changes the output speckle patterns by applying an electrical signal. The complex speckle patterns generated from the multimode planar waveguide are recorded into the N hologram filters and used as the code for destination. The feasibility of our method is experimentally demonstrated.