A compact silicon-based four-port coarse wavelength-division multiplexer (CWDM) with a footprint of 200×200 μm2 and an insertion loss of ∼2dB is demonstrated. This configuration can support each laser power of over 100mW without inducing silicon nonlinear effects. The design eliminates the need for interference in multiplexing different wavelength channels, resulting in significant fabrication tolerance and eliminating the requirement for phase shifters. The crucial components, such as power splitters/combiners and crossings, are designed and optimized using genetic-algorithm-based deep neural network (GDNN) inverse design methodologies to achieve minimal loss and broad bandwidth. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.