The design of quarter-wave retarders for the Dense Wave Division Multiplexing using
parallel mirrors coated with a single layer is presented. The output light from the device
is parallel to the input light and it is displaced by a distance d. The quarter wave retarder
overall reflection was in the range of 83%. Error analysis on the design is conducted. The
error analysis shows how changes on the angle of incident and the thin film thicknesses
effect the design of the retarders.