Graded-index plastic optical fiber for deformation sensing

This paper proposes the use of imperfected graded-index plastic optical fibers as sensing elements in deformation sensors. Use of a graded-index fiber instead of a step-index fiber for bending measurements resulted in an increase in sensitivity. Multi-loop configuration led to an even greater increase in sensitivity, reaching saturation after 15 half-loops. Imperfections implemented on the fiber further increased the sensitivity, although any variation of more than three imperfections, either all on one loop or each on separate loops, brought the sensitivity of the sensor to saturation. The maximal resolution obtained within a 25 mm radius range was 20 μm, with an even greater resolution at smaller ranges. These promising initial results indicate that sensors based on imperfected graded-index plastic optical fibers merit further study.