All Optical Fiber Sensor Based on Asymmetric Staggered Taper and Optical Fiber Bitaper Structure

A composite interferometric all-fiber sensor based on an asymmetric misaligned tapered multimode (ASTM) fiber configuration has been designed and investigated. This optical fiber sensor combines the asymmetric staggered taper (AST) structure, single-mode multimode single-mode (SMS) optical fiber and optical fiber bitaper (OFB) structure during preparation. The ASTM-OFB allows for efficient measuring of strains and temperature changes compared to conventional SMS fiber optic architecture. The experimental measurement results show that this new ASTM-OFB fiber optic sensor has two obvious resonance peaks near 1500 nm and 1580 nm, and its strain sensitivity is −37.85 pm/ $\mu \varepsilon $ and −71.92 pm/ $\mu \varepsilon $ respectively, which is about 42 times higher than that of the conventional SMS sensor; the temperature sensitivities in the two resonance peaks are 25.23 pm/°C and 26.47 pm/°C separately. The ASTM-OFB fiber optic sensors measure strain and temperature changes simultaneously with a temperature-strain crosstalk sensitivity of only $0.36~\mu \varepsilon /^{\circ }\text{C}$ ; its ASTM and OFB structures are prepared by common optical fiber fusion splicing mechanism, with a simple structure, controllable processing parameters and cost-effective.