Due to its fragility, fiber optic sensor (FOS) embedded into constructions made of carbon fiber reinforced polymer, can be broken both while it is manufacturing at the point of embedding into construction, and during its operation. This can lead to the inability to further monitoring of the construction strains. Usage of a specific thin Smart-layer for protection of FOS is proposed by the authors. For the Smart-layer manufacturing, 3D printing technology was used. The spectra of fiber Bragg grating (FBG) before and after layer printing have been analyzed, remaining compression strains were recorded. A mechanical test of a sample with surface-mounted FOS along with a Smart-layer was performed in order to measure the precision of strain detection by the Smart-layer. Some inaccuracy in strain detection was found during the analysis of the results. In order to find out the error in strain measured by a Smart-layer, a mechanical test of a full-sized bulkhead in a complex stress-strain state was performed.