In this study, we investigate an unclad single-mode fiber-optic biosensor by using COMSOL MULTIPHYSICS Finite Element Method (FEM) simulation. The key parameters of this study are the thickness and the refractive index (RI). The thickness of Au NPs was examined at 30nm, 40nm, and 50nm. Furthermore, the thickness of the analyte layer was also examined at 3μm, 4μm, and 5μm. This sensor was constructed using standard single-mode fiber. The cladding's middle section was removed, and gold nanoparticles (Au NPs) were deposited on it. It was found that at 50nm thickness of Au NPs, the confinement loss reached its maximum. Then, the Au NPs thickness was fixed at 50 nm and the analyte layer was changed. It was found that the confinement loss stayed nearly the same at the three thicknesses. The refractive index was also varied from 1.00027632 to 1.3403. After fixing the thickness of Au NPs and analyte layer at 50nm and 3μm, respectively, the sensitivity and resolution were measured and they were found to be 16129.03[nm/RIU] and 6.2×10-6[RIU], respectively, for colon tissue. This sensor provided theoretical analysis for experimental work. In addition to the simplicity of the design, this provides higher sensitivity.
