Abstract: A system for monitoring traffic across a structure. A fiber Bragg grating (FBG) reflects a light wavelength. A mounting mechanism connects the FBG to the structure, such that physical change of the structure changes a stress to the FBG that changes the light wavelength. And optical fiber carries a first light beam to the FBG and carries a second light beam from the FGB. This permits first light beam including the light wavelength to be received from a light source, and permits the first light beam to be altered into the second light beam by passing the light wavelength through the FBG, and permits the second light beam to be provided to a detector to sense the light wavelength present in the second light beam. From this the stress in the structure and information about the traffic across a structure can be inferred.