Fabrication of a screw-shaped plastic optical fiber for liquid level measurement

Abstract A screw-shaped plastic optical fiber (POF) is proposed as a liquid-level sensor. The screw-shape is fabricated on a POF by a simple heat pressing and twisting method. The liquid-level sensing performances of the so-obtained sensor with different structural parameters are evaluated. The results show that the highest sensitivity can reach up to 0.52 dB/mm in measuring the liquid with refractive index (RI) of 1.33 when the screw-shaped POF (without cladding) is fabricated by twisting the flat-POF with thickness of 600 μm and with the screw pitch of 3 mm. However, as the sensor is immersed in the water for a long time, the material water uptake will influence the liquid-level sensing performance, therefore the effects of material water uptake is studied as well. The results demonstrate that the proposed sensor is a low-cost solution for liquid-level measurement and with the features of easy fabrication, high sensitivity, and continuous measurement.