Sentence:  Since the early 1980s, considerable research effort has been devoted to the development of fiber optic (FO) <WSD>biosensors</WSD> because of their potential sensitivity, detection speed, and adaptability to a wide variety of assay conditions. 
Meaning of the word marked with <WSD> tags:  Any device that detects, records or transmits physiological data, especially data concerning the presence of chemical compounds (analytes)