Modeling of Graphene Coated D‐Shape Optical Fiber Sensor for Enhanced Vitiligo Detection Vis‐à‐Vis to Refractive Index Variations

This work numerically investigates a graphene‐coated D‐shape optical fiber sensor for early detection of vitiligo through refractive index (RI) sensing. A monolayer graphene layer is integrated on the polished fiber surface to exploit its strong optical confinement and surface interaction properties. Finite element method simulations are employed to study mode field profiles, effective RI variations, and confinement loss for analytes with RI values representing healthy and vitiligo‐affected skin tissues. The sensing mechanism relies on the excitation of the evanescent field at the graphene‐sensing layer interface, which exhibits a strong dependence on local RI changes associated with varying analyte concentrations. By judiciously optimizing all the geometrical parameters, the sensor achieves a high sensitivity up to 2000 nm/RIU, which significantly outperforms the uncoated fiber configurations. The study highlights the novelty of 2D‐material‐assisted fiber platforms for compact, noninvasive dermatological diagnostics, demonstrating their potential in real‐time vitiligo detection.