This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract-In many applications in 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 to be made. 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 300µm 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 non-embedded sensors and give excellent crosscomparison 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. Permanent repository link

In this paper, the embedding of fiber optic sensors in metals, by using both automatic and manual Tungsten Inert Gas welding (TIG) is discussed for nickel-and copper-coated Fiber Bragg Gratings (FBG) written into an optical fiber, as embedding such sensors in metals provides protection against environmental effects. In the investigation and analysis of the performance of a number of such sensors, copper-coated sensors were seen to lose their temperature and strain sensitivity while being embedded due to damage to the coating, while with a nickel coating the sensors in the fiber were found to withstand the process with a lesser effect on the sensor performance. The research has also shown that the Automatic TIG process used is less invasive than the manual TIG approach, although more expensive to implement.

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