Embeddable optical fiber sensor for simultaneous strain and temperature monitoring

We present an embeddable hybrid optical fiber sensor based on a cascaded extrinsic Fabry–Pérot interferometer (EFPI) and intrinsic Fabry–Pérot interferometer (IFPI) for simultaneous strain and temperature monitoring in high-performance composite materials. The sensor is fabricated using femtosecond laser micromachining and is embedded within bismaleimide composite laminates manufactured via an out-of-autoclave process. Experimental results demonstrate linear and decoupled responses to strain and temperature, with the EFPI showing minimal temperature sensitivity (1.7 pm/°C) and the IFPI exhibiting high temperature sensitivity (16.1 pm/°C). Strain sensitivities for both components were consistent at 0.6 pm/με in embedded conditions. The sensor maintained structural integrity and stable spectral response after exposure to 650°C, confirming its robustness for aerospace-relevant environments. A comparative analysis with existing fiber optic sensor technologies highlights the advantages of the proposed hybrid design in terms of compactness, thermal resilience, and ease of signal demodulation. These results demonstrate the sensor’s potential for integrated structural health monitoring of aerospace-grade composites.