Efficient, broadband optical coupling between optical fibers and photonic integrated circuits (PICs) poses a fundamental challenge in photonic system design. Among various coupling strategies, edge couplers offer low insertion loss, polarization-independent operation, and broad bandwidth. This thesis presents the design, optimization, and performance evaluation of edge couplers for a silicon nitride (SiN) photonic platform operating in the visible and near-infrared (NIR) spectral ranges. A fabrication-aware design is emphasized. The work is conducted within the framework of the IMEC SiN platform, and a comprehensive, simulation-based design methodology was developed using Ansys Lumerical tools. A detailed investigation and development of the simulation model yields more realistic results, including factors such as the substrate and the oxide interfaces.