We propose a design leveraging photonic crystal semiconductor optical amplifiers (PhC-SOA), harnessing its unique capacity to manipulate and govern light at the nanoscale. Optimization of critical parameters to enhance performance is pursued through the utilization of the particle swarm optimization (PSO) algorithm. Initially, a multiplexer was constructed using logic gates, achieving a peak output power of 1.94e−11 mW. A PSO algorithm was employed to find the optimal PhC-SOA parameters such as length of active layer, input energy, simulation steps, full width at half maximum (FWHM), carrier recovery time, linewidth enhancement factor, saturation energy, and linear gain to maximize performance. The peak output power obtained from the PSO-optimized multiplexer is 2.9e−11 mW. This paper demonstrates the performance of PhC-SOA-based all-optical multiplexers and the effectiveness of PSO in optimizing the performance of all-optical multiplexers and contributes to the advancement of optical communication systems for high-speed applications.