To address these challenges, we propose a novel direct measurement technique that offers greater robustness to variations in optical interfaces, while by-passing extinction ratio measurements. Our method enables a broadband and precise characterization of the directional. The design and fabrication of a compact, low-loss, broadband directional coupler (DC) based duplexer operating in the near-infrared (NIR) region are demonstrated. The duplexer exhibits high selectivity and coupling eficiency (CE), for target wavelengths of 1530 nm and 1653. 7 nm, making it. Directional couplers are essential components in inte-grated photonics.