We report on a thermal stability study of the resonant wavelength of fiber Bragg gratings fabricated by femtosecond laser. We propose a new method to analyze the decay of the central wavelength shift of Bragg gratings based on isothermal and isochronal processes up-to a maximum temperature of 800°C. The obtained thermal decay follows a typical power-law function, which allowed us to fit theoretical equations to our experimental data and simulate the refractive index decay. A method to mitigate this decay is proposed and the results demonstrate the potential of using femtosecond fiber Bragg gratings as high temperature sensors.
In this work, an optical fiber hydrostatic pressure sensor based in Fabry-Perot micro-cavities is presented. These micro structures were generated by the recycling of optical fiber previously damaged by the fiber fuse effect, resulting in a cost effective solution when compared with the traditional methods used to produce similar micro-cavities. The developed sensor was tested for pressures ranging from 20.0 to 190.0 cmH<sub>2</sub>O and a sensitivity of 53.7 ± 2.6 pm/cmH<sub>2</sub>O for hydrostatic pressures below to 100 cmH<sub>2</sub>O was achieved.