Sensing Characteristics of a Grating-Based Fabry-Perot Structure in a Biconical Tapered Fiber

Abstract

In this article, we present the sensing charac-teristics of a fiber Bragg grating (FBG) based Fabry-Perot (FP) structure in an acrylate coated biconical tapered fiber. The fiber-diameter was tapered down to $\mathbf{70}\ \mu \mathbf{m}$ using flame brushing technique followed by point-by-point writing of the FP structure within the fiber core using infrared femtosecond laser pulse irradiation. The sensing structure consists of two identical gratings separated by a small gap. The strain characteristics, ranging up to $3440\ \mu\varepsilon$, and the temperature characteristics, ranging up to 225 °C, have been investigated. The sensing sensitivities for strain and temperature were found out to be $2.32\ \mathrm{pm}/\mu\varepsilon$ and 8.86 pm/°C, respectively.