Abstract
The use of Nanostructured SPR sensors on Plastic Optical Fibers opens new challenges, because in an SPR sensor made by a continuous metal layer, the sensor's response is basically related to the metal properties at optical frequencies and to the waveguide characteristics. On the other hand, when a Nanostructured SPR sensor is used, the behavior is also related to the geometric parameters of the Nanostructures. Working on them it is potentially possible to tune the sensor's behavior. In this work the Authors present a numerical investigation in order to evaluate the behavior of two different SPR Nanostructured platforms, made by "long" gold Nanorods, and comparing them to an SPR sensor with a continuous gold layer. The difference between these two Nanostructured platforms is the orientation of the Nanorods, with respect to the light's propagation direction. The numerical results seem to indicate an increase of the sensitivity, when an SPR Sensor with long Nanorods is used, with respect to the sensor made by a continuous gold film, with some benefits.

Abstract
In this work, we report the design process for an optimal response of plasmonic sensors, exploiting gold nano-antenna array geometry realized on a D-shaped plastic optical fiber (POF). We have used different nano-slot arrays geometry, made by realizing rectangular slots on the gold layer. The numerical results obtained with different geometrical parameters, such as Slot's length, Slot's width and spacing, are presented. The aim of this work is to consider a different approach to obtain a plasmonic sensor in POFs, in which the geometrical parameters of the slots can modify the sensor's response to the different analytes placed and bound on the gold layer. The polarization of the Magnetic Field and the different patterns of the nano-slot array, for example different spacing among the slots, influence the plasmonic phenomena: Localized Surface Plasmon Resonance, Surface Plasmon Resonance or both. © 2016 The Authors.