Tapered Optical Fiber Coated With a Polyester Polymer as a Curvature Sensor

A fiber optic curvature sensor based on a tapered single-mode optical fiber coated with a polyester polymer (T-SMF-CPP) is proposed and experimentally demonstrated. Fabrication of the tapered optical fibers was realized by heating and stretching by a flame, and an airbrush was used to coat the surface of the tapered fiber with the polymer. The operating principle of the sensor was based on the interaction of the evanescent wave with the polyester polymer deposited on the tapered fiber. By adopting intensity demodulation in experiments, average sensitivities of -5.017 dB/m-1 and 5.862 dB/m-1 in the curvature ranges from 1.23 to 4.44 m-1 and from 4.64 to 7.54 m-1, respectively, were obtained for a fixed wavelength of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda =1572.45$ </tex-math></inline-formula> nm. The curvature of the sensor did not show a temperature dependence in the range [24-90 °C].