From Refractometry to Biosensing with Optical Fibres

This chapter focuses on optical fibre sensors (OFSs) that measure refractive index (RI) changes as main sensing mechanism. It analyzes the basic sensing concepts and parameters that can be used to assess the performance of OFSs. The chapter discusses optical fibre refractometers, where the RI changes encompass all the volume around the fibre, and optical fibre biosensors (OFBs), where the RI changes occur just on the functionalized surface of the fibre. It highlights the distinction between volume or bulk RI changes and surface RI changes to clarify the penetration depth of the evanescent field excited in the OFS. The chapter describes the three main groups of OFBs: immuno‐based biosensors, oligonucleotide‐based biosensors, and whole cell/microorganism‐based biosensors. Finally, future tracks and perspectives of OFSs are highlighted in order to provide some opportunities for OFSs to be used in the field of advanced diagnostics.