“…Optical fiber-based chemical sensors are enabled by functional chemical sensing coatings mostly on the fiber core or cladding, such as metallic films [53,102], oxides [103,104,105,106,107,108,109], polymers [49,110,111,112], nanomaterials [113,114,115], and metal-organic frameworks (MOFs) [116,117]. Figure 15 illustrates one example of the evanescent field-based chemical sensor [118]. The optical fibers can be etched, tapered, spliced, or side-polished to allow the light interactions with chemical sensing layers on the core or cladding and with the surrounding media [47,50,119].…”