Enhancement of a refractive index sensitivity by thinned the diameter of a plastic optical fiber assisted by a long period grating

A plastic optical fiber (POF) assisted by a corrugated surface long period grating (LPG) was proposed as a refractive index (RI) sensor, and the LPG was fabricated on a POF by a simple mechanical die press print method. An influence of the diameter of a POF assisted by an LPG to the RI sensitivity was investigated. A ray theory of geometric optics was used to simulate the LPG based RI sensors, and theoretical and experimental results showed that the RI sensing performance of the LPG could be effectively improved by flattening the POF for thinned it in one dimension, or drawing the POF for thinned it in two dimensions.