Two-photon 3D printed Fabry-Perot cavity combined with a femtosecond fiber Bragg grating on a single fiber for simultaneous sensing of pressure and temperature at high temperatures

In this work, a Fabry-Perot (FP) microcavity is printed on the tip of a single mode fiber (SMF) through the use of twophoton polymerization (2PP) process and a solmer resin. A femtosecond fiber Bragg grating (FBG) is also inscribed close to the 3D printed FP cavity using the Point-by-Point (PbP) direct writing process. This structure is then tested at temperatures ranging from 20°C up to 600°C in order to determine the thermal sensitivity of the FP and FBG to temperature. Using similar femtosecond FBG and 3D printed FP cavity but written on separate test fibers, a characterization in pressure is also performed. The FP cavity exhibits a sensitivity to pressure of 430 pm/bar at ambient temperature and a thermal sensitivity starting at 0.15 pm/°C at 20°C and 1.37 pm/°C at 600°C. The femtosecond FBG shows a pressure sensitivity of -0.364 pm/bar at 20°C, and a thermal sensitivity of 9.8pm/°C and 15.4pm/°C at respectively 20°C and 600°C.