Single-mode optical fibers with thin nickel coatings (outer diameter ∼350 μm) are successfully embedded into stainless steel (SS) 316 components using bespoke laser-based additive manufacturing technology. In our approach, we manufacture SS 316 components using selective laser melting, incorporating U-shaped grooves with dimensions suitable to hold nickel-coated optical fibers. Coated optical fibers containing fiber Bragg gratings for strain monitoring and temperature sensing are placed in the groove. The embedding is completed by melting subsequent powder layers on top of the fibers. Cross-sectional microscopy analysis of the fabricated components, together with analysis of the Bragg gratings behavior during fabrication indicates a strong substanceto-substance bond between coated fiber and added SS 316 material. Temperature and strain cycling of the embedded sensors demonstrates the ability of gratings to survive the embedding process, and act as sensing elements in harsh environments. In situ strain and temperature measurements from within the component are demonstrated for high dynamic stress levels and elevated temperatures (<400°C).Index Terms-Bragg gratings, embedded fiber sensors, laser melting, laser sintering, optical fiber sensors, stainless steel, strain sensors, temperature sensors. 0733-8724

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Fiber Bragg Grating (FBG) sensors are embedded into Stainless Steel (SS) 316 components using bespoke Selective Laser Melting (SLM) technology. SS 316 material is added on substrates by SLM, incorporating U-shaped grooves with dimensions suitable to hold nickel coated optical fibers. Coated optical fibers containing fiber Bragg gratings for strain monitoring are placed in the groove. Melting subsequent powder layer on top of the fiber completes the embedding. Strain levels exceeding 3 mɛ are applied to specimens and are measured by embedded fiber optic sensors. Elastic deformation of the steel component is reliably measured by the Bragg grating from within the component with high accuracy. During plastic deformation of the steel the optical fiber is slipping due to poor adhesive bonding between fused silica and metal surround.