Influence of Surface Roughness on the Sensitivity of a D-Shaped Optical Fiber-Based Refractive Index Sensor

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Abstract
This paper presents the evaluation of the influence of surface roughness on the performance of a refractive index sensor based on a D-shaped optical fiber. In addition, the manufacturing process of D-shaped sections on standard silica single-mode optical fibers with different rms roughness values is described. The surface roughness morphology generated by the abrasive process is measured by processing microscopic images using the Gwyddion software. A model for the surface roughness, using the third order Weierstrass fractal function, is proposed and simulated with COMSOL Multiphysics. Experimental and simulation results are presented. The results show that the surface roughness increases the device insertion loss, as expected, but contributes positively to the sensitivity of the refractive index sensor, reaching sensitivity levels of 148.87 dB/RIU with a resolution of 10-4 RIU. The good agreement between the computational and experimental results is highlighted. Due to the good figures of merit obtained, the optical sensor has potential of application in biochemical sensing.

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