The bending behavior of foam core sandwich composites has increasingly attracted attention and application in industries such as shipbuilding, aircraft and wind turbine industries. The main objective of this research work is the assessment of shear strain in a foam core beam by means of optical fiber sensors during bending test. Experimental studies were conducted on a PVC foam beam in which three optical fibers were embedded in a longitudinal plane across the thickness of the foam core; straight optical fibers measure strains due to the tension/compression load, whereas the sinusoidal fibers catch strains due to the shear load. Finite element model (FEM) was used to predict strain levels in order to validate and explain optical fiber sensor measurements from 3-and 4-point bending tests. The concordance of the shear properties identified by optical-fiber sensor results and obtained by finite element simulation was evaluated to validate the new developed technique of characterization. Results shows good agreement between the experimental and numerical responses.