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Stress measurement in epoxy polymers during molding and curing is presented by use of embedded fiber optic Bragg grating (FBG) sensors. By mechanical coupling between polymer and fiber the FBG sensor enables monitoring of encapsulation induced strains and forces acting on the embedded electrical components. Determination of gel point and material shrinkage directly in the mechanical environment of the product and production line is possible as well as structural health monitoring of the encapsulated electronic components. It is shown that the grating is able to detect delaminations within the polymer during curing and post curing processes. We successfully tested fiber optic strain sensors in industrial transfer molding processes.