An angle sensor based on polymer optical fibers with cladding doped by rhodamine B

Abstract

The present study proposes to utilize rhodamine B (RhB) doped polymer optical fibers (POFs) for angle sensing. POFs are doped by immersing the fiber in the aqueous solution dissolved with RhB at elevated temperatures so that RhB molecules diffuse into the fiber. It is found that most RhB molecules are in the cladding. That is, only the fiber cladding is doped by RhB. The doping process involves no physical modification to POFs, thus the sensor fabrication process is facile and mechanical properties of POFs are not impacted. Two major factors that influence the angle sensing performance of the sensor are investigated, namely, the bending radius and the fiber diameter. Along with experimental study, ray-tracing simulation is also conducted to investigate their influence. Bending radius of 1, 2, 3 mm and two POFs in diameter of 250 and 500 μm are tested. In addition, POFs with different doping concentrations are fabricated and tested to examine its influence on the sensitivity. Among all fabricated sensors and various sensing conditions, the highest angle sensitivity of 0.0519 dB/° is achieved by the doped POF in diameter of 500 μm for the bending radius of 1 mm. It isn’t the highest among similar technologies, but easy fabrication process and embedding would make it attractive for practical angle sensing applications.