Hi-Bi optical fiber sensor for measuring small weight

An optical fiber sensor consisting of short sample of experimental Hi-Bi optical fiber integrated between two single mode (SM) optical fibers is proposed and experimentally demonstrated. The experimental fiber consists of core with diameter equals 8.5 μm and the two side Stress Applied Part (SAP) of diameter 25 μm. The SAPs are made of Al-Ladoped silica. The birefringence of the fiber is 3.19·10-4. We measured spectral distribution of intensity at the output of the SM fiber as function of the analyzer's adjustment angle and the suitable position of the analyzer was determined. Then we applied the bodies with weights up to 100 g on the fiber for two significant positions of SAPs: SAPs were next to each other and above each other. Evaluation of the measurements were done by the peak-to-peak amplitude of optical power difference (in dB) of two measurement for which we determine the applied force (weight). The sensitivities were determined to be 0.081 dB/g for SAPs next to each other and 0.037 dB/g for second position of SAPs, respectively. From the results it follows that the sensor could be used not only for determination of lateral force but also for determination of applied force position.