Highly sensitive curvature sensor based on long period fiber grating with alternately splicing multiple single/multimode structure

A highly sensitive curvature sensor made of a novel long period fiber grating (LPFG) is presented and experimentally demonstrated. It is constructed by splicing multiple single mode fibers (SMFs) and multi-mode fibers (MMFs) alternately (MS/MA). The measurement result shows that it has a high sensitivity of −22.4 nm/m−1 in the range from 0.223 m−1 to 4.358 m−1. It can measure curvature on all direction due to the symmetric structure. The proposed sensor was also insensitive to the temperature, whose temperature sensitivity was around −0.015 nm/°C in the range from 40 °C to 200 °C. The advantages of high curvature sensitivity and low temperature sensitivity make it has a great potential to measure curvature in practical application with high resolutions.