GaN-based devices have developed significantly in recent years due to their promising applications and research potential. A major goal is to monolithically integrate various GaN-based components onto a single chip to create future optoelectronic systems with low power consumption. This miniaturized integration not only enhances multifunctional performance but also reduces material, processing, and packaging costs. In this study, we present an optoelectronic on-chip system fabricated using a top-down approach on a III-nitride-on-silicon wafer. The system includes a near-ultraviolet light source, a monitor, a 180° bent waveguide, an electro-absorption modulator, and a receiver, all integrated without the need for regrowth or post-growth doping. 35 Mbit/s optical data communication is demonstrated through light propagation within the system, confirming its potential for compact GaN-based optoelectronic solutions.