Investigation of a macrobending micro-plastic optical fiber for refractive index sensing

This paper investigates a refractive index (RI) sensor based on a macrobending micro-plastic optical fiber (m-POF), which is used as a sensitive probe. The m-POFs are fabricated from commercial POFs using a heating and pulling method. The m-POFs have diameters of approximately 20-40 μm and act as multimode fibers at visible wavelengths. The macrobending structure of the m-POFs is simulated and optimized using the ray tracing method. The RI sensitivity and the range of RI measurements are affected by the structure parameter R/ρ, which is the ratio of the radius of curvature of the macrobending fiber to the radius of the fiber itself. A linear RI sensing response is obtained when R/ρ=20 and the sensitivity reaches 500%/RIU. The experimental results coincide well with the simulation results.