Electrical component speed is a major constraint in high-speed communications. To overcome this constraint, electrical components are now being replaced by optical components. The application of optical switching phenomena has been used to construct the design of the D flip-flop and T flip-flop based on the electro-optic effect in a Mach-Zehnder interferometer (MZI). The MZI structures show the powerful ability to switch the optical signal from one output port to the other. Hence, it is possible to construct some complex optical combinational digital circuits using the electro-optic-effect-based MZI structure as a basic building block. This paper constitutes the mathematical description of the proposed device and thereafter compilation using MATLAB. The study is carried out by simulating the proposed device with the beam propagation method.