With the Ray-tracing technique, the variation of the radiant energy with the distance between the emitter and the receiving area was calculated.As the distance increases, the radiant energy radiated on the receiving area decreases.Besides, the variation of the radiant energy with the aperture width in the housing and the receiving area was calculated as well.The results are helpful to understand the optical characteristics of the switch.Moreover, further calculations can provide useful references for the determination of the housing param-eters during the EO switch design.