D-Shaped Plastic Optical Fiber Sensor for Testing Refractive Index

In this paper, a D-shaped plastic optical fiber is fabricated by means of side-polishing technique for refractive index (RI) sensing. The principle of operation is based on the exploitation of the evanescent wave interaction of the propagating light with the external environment, resulting in optical transmission attenuation. Transmission loss is measured when the RI of the external medium changes from 1.333 to 1.455, exhibiting a good linear relationship between them. By changing the depth of the D-shaped groove and the curvature radius of the optical-fiber probe, the sensor sensitivity is optimized. This D-shaped fiber sensor is relatively simple of construction and low cost, which makes it attractive for RI sensing in biochemical region.