Modified signed-digit (MSD) numbers offer convenient parallel addition and subtraction of bits. The parallel addition of any two MSD numbers, no matter what the values of their bits may be, requires only three bit-pattern transformations. To perform such transformations optically, however, MSD data must be represented in a form suitable for cascade connection. Proposed here is a new cascade-connective MSD optical processor. Adding principles are successfully demonstrated by using an optical threshold device array in addition to new computer-generated holograms that are adjusted to equalize the intensity of their diffracted light beams.