Application of etched fiber strain gauges to low-cost on-board vehicle load monitoring

We investigated the use of wavelength compensated coupler sensors and etched optical fiber strain sensors to provide an economical on-board load indicator for passenger vehicles. Cost considerations favored the etched fiber sensor. Manufactured sensors were evaluated experimentally by straining them on a cantilever beam. For strain smaller than 600 microstrain the output of a 10 segment sensor was linear with a typical gauge factor of minus 57. Bending losses in the fiber sensor became more pronounced for larger strain. Proper weighting of the outputs of the front and back sensors on the vehicle ensures a monotonic relationship between the sensor output and load. Difference-over-sum processing minimizes the effects of sensitivity to common- mode perturbations such as temperature and source intensity changes.