FBG Incorporated Side-Open Fabry–Perot Cavity for Simultaneous Gas Pressure and Temperature Measurements

A dual-parameter sensing structure based on a fiber Bragg grating (FBG) incorporated side-open Fabry-Perot cavity (FPC) is proposed and experimentally demonstrated for simultaneous measurements of gas pressure and temperature. The side-open FPC consisted of a micro-piece of chemical etched side-hole fiber acts as a pressure sensing unit. Two samples with different cavity lengths of 60 μm and 100 μm were fabricated and tested for gas pressure and temperature sensing in the experiment. Linear gas pressure responses of 4.063 pm/kPa and 4.071 pm/kPa in a large measuring range of 0-1000 kPa were obtained, respectively, which agree well with the theoretical analysis. Meanwhile, the temperature cross-sensitivities were measured as 214 Pa/° and 204 Pa/°. As a local temperature monitor, the incorporation of a short FBG in the leading single mode fiber was used to compensate the temperature cross-sensitivity of the sensor. This kind of compact and highly sensitive fiber sensor is appropriate for simultaneous gas pressure and temperature sensing in harsh micro environment.