Abstract: Glass fiber reinforced plastics (GFRP)laminates containing the extrinsic fabry-perot interferometr (EFPI) sensor in its middle plane were made for experiments. Three-point bending tests of the laminate were performed to obtain the relationship between the bending moment and the strain output from the sensor. Microscopic examination of the cross section containing the sensor was carried out. Finite element method (FEM) strain analysis was also performed to obtain the strain of the sensor embedded at the off-center position obtained from the microscopic observation. From these results,it is found that the strain output from the EFPI sensor is larger than that calculated for the off-center sensor. This discrepancy shows that the bending moment affects the measuring ability of the sensor.