LAUSR

In many applications in the industry, securely attaching fiber optic sensors to metallic structures is important for optimum monitoring, overcoming the limitations of glues and adhesives which are known to degrade under certain circumstances. To avoid that problem, creating a metallic bond to attach the sensors securely to the metal surface is important. Commercial fiber optics with metal coatings can be used but it is important not to damage the sensor itself which is written in the thin optical fiber. In this work, an alternative laser cladding technology has been studied for embedding metal-coated fiber optics into which fiber Bragg grating (FBG) sensors have been written. A three-step strategy was selected for embedding the metal coating fibers to create the best conditions to allow high-quality measurements. This has been seen to allow good control of the embedding process to be achieved and to minimize the thermal and mechanical stress generated. The research undetaken has shown that it is possible to embed Cu- and Ni-coated fiber optics containing sensors to over 300 μm with low losses, of between 0–1.5 dB (or 0–30%) and yet still enable satisfactory strain and temperature measurement results to be obtained. The research has shown that both Ni- and Cu-coated FBG-based fiber optic sensors could be embedded successfully and shown to give good mechanical and thermal response to similar nonembedded sensors and excellent cross-comparison with the conventional gauge used for calibration. The results are, therefore, particularly encouraging for the use of sensors of this type when incorporated to create metallic “smart structures” achieving durability of the sensors through the use of this innovative technique.