A cascaded fiber sensor for measuring different curvature ranges based on the cladding mode resonance in double-cladding fiber

摘要

A cascaded fiber sensor for measuring different curvature ranges based on the cladding mode resonance in double-cladding fiber is proposed. It is formed by double-cladding fiber and single-mode fiber. Based on the evanescent wave coupling principle, the cladding mode resonance phenomenon in double-cladding fiber is illustrated. The transmission spectrum with different length are also analyzed. The experimental results show that the resonance wavelength changes with the length of double-cladding fiber. When the fiber length is 22 mm, the transmission spectrum is blue-shifted as the curvature increases in minor range of 0-0.204 m(-1), the corresponding curvature sensitivity can be up to -19376.48 pm/m(-1). When the fiber length is 20 mm, the corresponding curvature sensitivity can be up to -4161.73 pm/m(-1) as the curvature increases in large range of 0-1.06 m(-1). The proposed curvature sensor has the characteristics of simple structure and high sensitivity, so it has a good application prospects in large bridges, industrial buildings and other curvature measurement situations.