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Fiber optical components such as fiber gratings, fiber interferometers, and in-fiber Fabry-Perot filters are key
components for optical sensing. Fiber optical sensors offer a number of advantages over other optical and electronic
sensors including low manufacturing cost, immunity to electromagnetic fields, long lifetimes, multiplexing, and
environmental ruggedness. Despite the advantages of purely passive optical components described above, fiber sensor
performance and applications have been limited by their total passivity and solid-core/solid cladding structure
configurations. Passive sensors can only gather limited information. Once deployed; set point, sensitivity, trigging time,
responsivity, and dynamic range for each individual fiber sensor cannot be adjusted or reset to adapt to the changing
environment for active sensing. Further, the fiber sensor sensitivity is also limited by the traditional solid core/solid
cladding configuration.
In this paper, we present a concept of active fiber sensor that can directly powered by in-fiber light. In contrast to a
passive sensor, optical power delivered with sensing signal through the same fiber is used to power in-fiber fiber Bragg
grating sensors. The optical characteristics of grating sensors can then be adjusted using the optical energy. When optical
power is turned off, in-fiber components can serve as traditional passive sensor arrays for temperature and strain
measurements. When optical power is turned on, the fiber sensor networks are capable of measuring a wide array of
stimuli such as gas flow, wall shear stress, vacuum, chemical, and liquid levels in cryogenic, micro-gravity, and other
hostile environments. In this paper, we demonstrate in-fiber light powered dual-function active FBG sensor for
simultaneous vacuum, hydrogen fuel gas, and temperature measurement in a cryogenic environment.
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