Using the finite element method and COMSOL version 5.5, a three-bit binary to gray converter with three plasmonic substructures and five input and three output ports was designed. Using a 520n m×200n m metal-insulator-metal plasmonic structure, the plasmonic converter was developed. In this configuration, the transmission threshold (T t h r e s h o l d ) is set to 45% at an operating wavelength of 1310 nm. Utilizing the modulation depth, contrast ratio (CR), and insertion loss criteria, the effectiveness of the plasmonic converter is evaluated. For the first, second, and third output terminals, the CR has respective values of 40.1 dB, 9.3 dB, and 9.2 dB.