A review on simple and highly sensitive plastic optical fiber probes for bio-chemical sensing

•Low-cost and portable POF sensors have been recently developed.•POF-probes can be used in combination with several types of receptors.•POF sensors exploit different optical phenomena as plasmon and evanescent wave.•Highly reliable and robust monitoring of different substances can be carried out. A review on bio-chemical label-free sensing applications based on receptors combined with multimode plastic optical fibers (POFs) is carried out. In particular, this work focuses on different kinds of POF intrinsic sensors used in transmission mode, exploiting various types of receptors and useful in several application fields. The sensor structures and the sensing mechanisms of different simple, highly sensitive, and low-cost POF probes are reported and compared. Moreover, different kinds of chemical and biological receptors combined with POF probes, highlighting the advantages and disadvantages of each receptor, are presented in detail. More specifically, the chosen POF sensing platforms, including low-cost and simple interrogation setups, are described showing their ability to monitor specific receptors exploiting intensity variation techniques and plasmonic phenomena, as well. Finally, a prospect of future developments of biochemical sensors with multimode POFs is discussed.