Macrobending loss in wrapped fiber optic for load detections

Macrobending-based fiber optic sensors are constructed to measure load. Two sensor models are investigated to find a better linearity response; i.e., narrow helix-shaped and wide helix-shaped sensors. The sensing mechanism of those sensors is due to a macrobending loss of the traveling light inside the optical fibers. This work employs a distributed feedback laser diode and a Ge-based photodetector as the light source and the light loss detector, respectively. The results indicated that the linear response to a static-load exposure apparently can be improved by spacing the coiled fiber on the silicon rubber at a specific diameter. Several investigations reveal the optimum diameter and fiber spacing to design an accurate fiber optic based sensor for load measurement. A sensitivity of 398V/kg/cm² and 100V/kg/cm² are obtained on a diameter of 25 mm and 38 mm cylindrical rubber with fiber spacing of 15 mm. Furthermore, an assessment under a dynamic object can exhibit uniform responses presenting minor deviations.