An Optical Combination Method for Resolving Axial and Transverse Force Interference Using Tapered Fiber Bragg Grating

Crosstalk noise between the two force components (axial and transverse) and temperature is always present when the fibre Bragg grating (FBG) sensor technology is utilized in many sophisticated equipment. To address this, we proposed a theoretical method that decouples the two force components while eliminating the effect of temperature, using a combination of modified FBGs and a bandwidth modulation mechanism. Our previous study showed the first step in our continuous effort to prove the concept. In this study, the second part of proving the decoupling approach while avoiding the temperature effect is proved experimentally. In addition to the tapered FBG (TFBG) in its neutral axis, a hollow shaft prototype that resembles the construction of several medical surgery equipment is being developed further to include a linear chirped FBG (CFBG) along its shaft's surface. The experimental results demonstrate that the estimated axial and transverse force values are consistent with their actual values, with RMS errors of less than 0.32 N and less than 0.16 N, respectively, over the range of (0 N – 10 N). The presented method can potentially be extended to small surgical instruments such as ophthalmia’s needle and ablation catheter.