Fig. 5: Electrochemical surface-plasmon-resonance sensing principle and experimental demonstration with an gold-coated TFBG optical fiber sensor.

a Experimental setup of a plasmonic fiber-optic sensing system for monitoring the SOC of supercapacitors. b Photographs of the configuration for the supercapacitor and (c) gold-coated fiber-optic sensing probe. SEM images of (d) the MnO2 electrode and (e) the corresponding magnified image. f Schematic of the measurement of the charge–discharge process of supercapacitors by a plasmonic gold-coated TFBG fiber-optic sensor