High-temperature, chemically harsh processes underpin a wide range of applications ranging from power generation, infrastructure monitoring, chemical manufacturing, and many others. For such processes, in situ sensor data is a valuable tool for both optimization and safety, however, traditional sensor platforms can be limited in terms of stability at high temperatures or under highly corrosive, reducing, or oxidizing chemical conditions. Optical fiber-based sensing offers a unique tool for this type of harsh environment sensing application. Off-the-shelf silica fiber itself is highly stable up to ~800 °C, under a wide range of chemical conditions; while single crystal optical fiber expands this operational range even further, to temperatures well above 1000 °C. Work will be presented on the utilization of n-type semiconducting oxide thin films on single crystal sapphire fiber for the evanescent field-based sensing of reducing gas streams at temperatures up to 900 °C. The role of oxygen defects on the electrical and optical properties of the relevant films will be discussed, providing a theoretical background for the observed sensing response, time-dependence, and stability. Doped SrTiO3 systems (LaxSr1-xTiO3) will be discussed for hydrogen sensing at high temperatures. Strategies and challenges associated with pushing sensor and single crystal fiber performance above 1000 °C will also be discussed.
To achieve high-efficiency turbine engine operation, turbine combustors must operate with a finely controlled fuel-air ratio near the flame extinction limit, informed by feedback from reliable in-situ temperature measurements. Distributed temperature sensing up to 900-1000 o C using Raman optical-time-domain-reflectometry (ROTDR) with single-crystal optical fiber is demonstrated in a combustion test rig. The distributed temperature sensing (DTS) system utilizes sapphire and yttrium-aluminum-garnet (YAG) fibers which were optimized to improve the signal-to-noise ratio (SNR) of collected Raman signals. Estimation of the SNR of recorded signals and predicted errors were analyzed to simulate the effect of a variety of system parameters and experimental conditions. Enhancement of the SNR through selective doping of the singlecrystal fiber was investigated. The expected Stokes and Anti-Stokes collection efficiencies using high-sensitivity avalanche photodiodes were calculated for the optimized optical path. Denoising algorithms of the SNR were developed by exploring noise sources which constrain detection capability via uncorrelated and multiplicative noise. Calibration techniques have been implemented to correct the dynamic variation of the optical loss with temperature in the singlecrystal fibers to obtain the calibration parameters and temperature profile.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.