Embedding of Fiber Optic Sensors in Metal Parts by Laser Welding and Additive Manufacturing: A Review

Metal components with integrated sensing technologies are currently an interesting yet challenging process. The industry’s demand for embedded sensors for long-lasting monitoring of structures is stimulating the development of smart components within the Industry 4.0 framework. In this context, one of the most relevant technologies for structural health monitoring is based on optical fibers, as the latter have several intrinsic advantageous properties. However, embedding optical fiber-based sensors for their use in harsh environments may be significantly challenging. For instance, when integrating such sensors into metallic components, such processes often involve metal melting due to high temperatures. This paper provides a critical review of the embedding process of optical fiber-based sensors into metal components using laser-based techniques as a manufacturing method, with a particular emphasis on the diverse embedding strategies found in the literature. This paper also addresses several methods for the metallic coating of optical fibers, as the latter has been proven necessary in order to protect the fiber during the embedding process. Such analysis includes the study of the effect of different materials, thicknesses, and manufacturing techniques as well. All in all, this work aims to serve as a guide for achieving optimal fiber embedding, tailored to specific requirements and resources of each case, in which the challenges associated with fiber embedding in metal components are highlighted and recommendations for future research are outlined.