Optical fiber biosensors could be used to develop Point-Of-Care Tests (POCTs) for detecting viruses and bacteria in several matrices. In particular, the Surface Plasmon Resonance (SPR) and Localized SPR phenomena (LSPR) can be excited by exploiting low-cost and small-size optical fiber chips. Generally, SPR or LSPR sensors are realized using several kinds of modified optical fibers (silica, plastic, or specialty) or exploiting other optical waveguides (e.g., slab, spoon-shaped waveguides, etc.). More specifically, optical fiber sensors can be classified as intrinsic or extrinsic. In the “optical fiber intrinsic sensors”, the sensing area is realized in the optical fiber directly, such as in the case of plasmonic platforms based on D-shaped plastic optical fibers (POFs), tapered optical fibers, U-bend POFs, or light-diffusing fibers (LDFs). On the opposite, when the optical fiber is used as a mere waveguide allowing the launch of light to the sensing region and its collection, it is defined as “optical fiber extrinsic sensors”, like in the case of the plasmonic sensors realized by Cennamo et al. via POFs combined with spoon-shaped waveguides, 3D-printed platforms, bacterial cellulose waveguides, nano-gratings and InkJet printed based chips. To realize optical biosensor chips for viruses and bacteria detection, both intrinsic and extrinsic plasmonic POF sensors can be efficiently combined with receptors specific for membrane proteins, either biological (e.g., antibodies, aptamers, enzymes, etc.) or synthetic (e.g., molecularly imprinted polymers), to build groundbreaking POCTs.