Environmental monitoring requires rapid and stable methods for detecting chemical contaminants in water and air systems. Optical biosensor platforms offer a practical sensing approach because they convert molecular interactions into measurable optical signal changes, including absorbance, fluorescence, luminescence, and refractive index variation. This paper evaluates the performance of optical biosensor platforms for environmental contaminant detection under controlled laboratory conditions. The study focuses on two performance measures: detection sensitivity and measurement stability. Laboratory experiments used blank, low concentration, and higher-concentration exposure conditions, and the resulting optical signals were examined through baseline comparison, normalized response analysis, and repeatability assessment. The results showed stable baseline signals and clear response shifts after contaminant exposure. Low-concentration samples remained distinguishable from blank conditions, while higher concentrations produced stronger optical variation. Repeated measurements also showed acceptable consistency across exposure levels. These findings indicate that optical biosensor platforms can support low-level environmental contaminant detection when signal response and stability are evaluated together. The study presents a structured framework for assessing optical biosensor suitability in environmental monitoring applications.