Browsing by Author "Webb, David J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Measuring water activity of aviation fuel using a polymer optical fiber Bragg grating
    (Society of Photo-optical Instrumentation Engineers, 2014-06-02) Zhang, Wei; Webb, David J.; Carpenter, Mark D.; Williams, Colleen
    Poly(methyl methacrylate) (PMMA) based polymer optical fiber Bragg gratings have been used for measuring water activity of aviation fuel. Jet A-1 samples with water content ranging from 100% ERH (wet fuel) to 10 ppm (dried fuel), have been conditioned and calibrated for measurement. The PMMA based optical fiber grating exhibits consistent response and a good sensitivity of 59±3pm/ppm (water content in mass). This water activity measurement allows PMMA based optical fiber gratings to detect very tiny amounts of water in fuels that have a low water saturation point, potentially giving early warning of unsafe operation of a fuel system
  • Thumbnail Image
    ItemOpen Access
    Performances of PMMA-based optical fiber bragg grating sensor in extended temperature range
    (MDPI, 2021-05-23) Zhang, Wei; Webb, David J.
    PMMA based optical fiber Bragg grating (POFBG) sensors are investigated in an environmental chamber with controlled temperature and relative humidity at temperature extended to 70 °C. At below a critical temperature of 50 °C the POFBG sensor exhibits good linearity and sensitivity for both temperature and humidity sensing. Nonlinear responses are observed at higher temperature, giving rise to varying, reduced magnitudes of sensitivities. An important feature of POFBG humidity sensing is observed at above critical temperature where the POFBG humidity sensitivity turns from positive to negative. A theoretical model based on Lorentz–Lorenz equation is presented to estimate the dependence of POFBG refractive index on temperature and relative humidity. The experimental results qualitatively agree with the theoretical analyses