Abstract: A fiber optic sensor for measuring strain on and within structures. The sensor includes an optical fiber, two reflective markers, and two thin layers of carrier material. The optical fiber is looped multiple times within the two thin layers of the carrier material. The optical signal circulates multiple times through the sensing region, as it is travels through the multiple loops of optical fiber within the carrier layers. The fiber optic sensor can be embedded within a structure, as that structure is being fabricated, or it can be attached onto a preexisting structure. An optical signal generated from a source such as a laser is input into one end of the optical fiber. The signal is reflected at reflective markers at predetermined positions in the optical fiber. The time delay of the signals received back is then analyzed to calculate the strain in the structure.