Abstract
This paper reports a technique to enhance the magnitude and high-temperature stability of Rayleigh back-scattering signals in silica fibers for distributed sensing applications. With femtosecond laser radiation, more than 40-dB enhancement of Rayleigh backscattering signal was generated in silica fibers using 300-nJ laser pulses at 250 kHz repetition rate. The laser-induced Rayleigh scattering defects were found to be stable from the room temperature to 800 °C in hydrogen gas. The Rayleigh scatter at high temperatures was correlated to the formation and modification of nanogratings in the fiber core. Using optical fibers with enhanced Rayleigh backscattering profiles as distributed temperature sensors, we demonstrated real-time monitoring of solid oxide fuel cell (SOFC) operations with 5-mm spatial resolution at 800 °C. Information gathered by these fiber sensor tools can be used to verify simulation results or operated in a process-control system to improve the operational efficiency and longevity of SOFC-based energy generation systems.
Highlights
Solid oxide fuel cell (SOFC) technology is a promising and versatile energy generation scheme
The distributed fiber sensor demonstrated in this paper provides a new and valuable tool to measure the constantly-evolving solid oxide fuel cell (SOFC) temperature profile, which will lead us towards optimizing the efficiency and longevity of SOFC-based energy systems in the future
While the ultrafast lasers have been used previously to fabricate fiber Bragg grating (FBG) point sensors, this paper presents a far simpler technique to produce distributed fiber-sensors to perform continuous temperature sensing with 5-mm spatial resolution in high temperature, highly reactive hydrogen-containing environments
Summary
Solid oxide fuel cell (SOFC) technology is a promising and versatile energy generation scheme. This paper presents a manufacturing method to produce distributed fiber sensors with high spatial resolution using ultrafast laser pulses to perform continuously scan of the fiber cores It does not require point-by-point periodic laser writing or holographic laser exposure to form fiber Bragg gratings with nanometer precision in grating periods. The resultant fibers with laser-enhanced Rayleigh scattering profiles, due to the formation of nanogratings, can perform distributed temperature sensing with 5-mm spatial resolution at 800 °C in highly reactive fuel gas (hydrogen) stream. Using this powerful sensing tool, we demonstrate distributed temperature measurement in an operating SOFC system. Information gathered by this fiber sensor tool can be compared with simulation results to aid in SOFC system design, and improve the operational efficiency and longevity of the SOFC system
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