Carbon fiber reinforced polymer (CFRP) structures increasingly require embedded structural health monitoring (SHM) solutions capable of distinguishing mechanically induced strain from thermally induced effects. In this context, piezoresistive polymer-composite fibers represent a promising sensing platform, although conventional single-core architectures provide only one electrical signal and therefore offer limited intrinsic discrimination between coupled stimuli. This thesis investigates the development of a dual-core piezoresistive sensing fiber intended to generate differentiated electromechanical and thermoresistive responses as a basis for future strain-temperature decoupling. The proposed fiber consists of two conductive polycarbonate/carbon nanotube (PC/CNT) cores embedded within an insulating polyetherimide (PEI) cladding and was fabricated through thermal drawing.