Optical fiber biosensors based on the surface plasmon resonance (SPR) phenomenon are generating increasing interest due to their capability of real-time monitoring of analytes in a biocompatible, label-free, stable, and cost-effective manner. Recently, field localization techniques using nanostructures or nanoparticles have been investigated on optical fibers for further sensitivity enhancement and significant. This study reports the development of a fiber-optic localized surface plasmon resonance (FO-LSPR) sensor incorporating a three-dimensional micropillar array functionalized with gold nanoparticles. In fact, SPR optical fiber biosensors are becoming very.