Fiber strain sensor based on compact in-line air cavity fabricated by conventional single mode fiber

A Fabry-Perot micro-interferometer has been designed based on the conventional single-mode fiber end fusion method for measuring strain along the fiber. During the splicing process of single-mode optical fiber, the uniformly coated glycerine on the end face of the fiber is vaporized due to the high temperature of arc discharge to form a spherical air microcavity (Fabry-Perot cavity). The experimental results show that the proposed sensor can determine the strain during 0-1.2 N with a linear response and the corresponding sensitivity of similar to 3.25 nm/N. The Fabry-Perot micro-interferometer strain probe proposed in this paper is simple to manufacture, compact in structure and easy to integrate. It has the promising potential in exploring the intelligent wearable devices for real-time monitoring of micro-strain changes such as pulse, blood pressure, and respiration.