Study of bundled fiber based displacement sensors using theoretical model and fitting function approaches

The performance of optical fiber displacement sensors with a pair of probe is theoretically and experimentally demonstrated using a developed theoretical model and fitting function approaches. The displacement measurement is carry out by using the modulated 633nm light source in conjunction with lock-in amplifier to reduce the dc drift and interference of ambient stray light. Based on this measurement, a fitting curve is obtained, which is then compared with the theoretical results. The sensor has two slopes with a linearity of more than 99% for both theoretical and fitting approaches. With the fitting approach, linearity ranges of 500 mu m and 1450 mu m are obtained for the front and back slopes respectively. On the other hand, linearity ranges are obtained at 600 mu m and 1550 mu m for front and back slopes, respectively using the theoretical approach. The sensitivity (in arb. Units x 10(3)) for the theoretical and fitting approaches are obtained at 1.70 and 1.92, respectively for the front slope and 0.36 and 0.40 respectively for the back slope.