Adaptive Refractive Index Measurements via Polymer Optical Fiber Speckle Pattern Analysis

In recent years, the development of highly sensitive and cost-effective sensing technologies has gained significant attention in the field of optical sensors. This article introduces a novel approach for refractive index measurement utilizing a polished perfluorinated polymer optical fiber (POF). The proposed sensor leverages the unique optical characteristics of speckle patterns formed on the end face of the fiber to precisely determine refractive index variations in surrounding media, which were found to be several orders more sensitive compared to previous studies. The refractive index of the specific fiber material makes the sensor ideal for liquid analysis. The proposed sensors were successfully evaluated for refractive index values up to 1.511, and the calibration curves of the sensor were developed. Finally, it is shown that the sensitivity can be tailored according to the application with proper signal processing treatments.