An optical fiber sensor based on the resonant coupling between a surface plasmon wave and a guided mode of the optical fiber sensor has been reported. A technique based on the surface plasmon resonance phenomenon offers a sensitive method for studying the stability of optical sensors. In this work, we consider a layered structure consisting of three-layer optical waveguides incorporating gold-aluminum coating layers. Tests including exposing gold-aluminum films to water have been studied. Experimental and theoretical results have been mutually compared, and the operation characteristics of this novel sensing device have been briefly described.