Ultra-high sensitivity and temperature-compensated Fabry–Perot strain sensor based on tapered FBG

Abstract A novel ultra-high sensitivity and temperature-compensated in-line Fabry–Perot (FP) strain sensor based on tapered FBG-in-capillary structure is proposed and experimentally demonstrated. The proposed sensor can be easily fabricated by inserting a fiber taper with FBG into the capillary, making it possess the ultra-long active length and the ultra-short interference length to achieve strain sensitivity enhancement. In addition, the strain-free FBG in the capillary is a good candidate for temperature compensation. The strain sensitivity of this structure is as high as 1129.44 pm/µe, which is about two orders of magnitude higher than that of common FP strain sensors reported. The crosstalk of the temperature can be compensated by sensitivity coefficient matrix demodulation. Such structure has ultra-high sensitivity, good linearity, temperature-compensation, robust and easy-fabrication, which is expected to have potential applications in strain sensing.