Presentation
14 March 2018 An integrated optical fiber device for harsh environment refractometry at indices above silica for monitoring hydrocarbon fuels (Conference Presentation)
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Abstract
Integrated Optical Fibre (IOF) allows for robust planar integration and seamless monolithic coupling. Fabrication is achieved through an adapted Flame Hydrolysis Deposition (FHD) technique, which forms a ruggedized glass alloy between the fibre and planar substrate. It has been previously demonstrated as a low linewidth external cavity lasers diode and a hot-wire anemometer, inherently suitable for harsh environments. This work looks at implementing the platform for harsh environment refractometry, in particular monitoring hydrocarbon fuels in the C14 to C20 range (e.g. Jet A1 and diesel). The platform uses SMF-28 fibre and direct UV written Bragg gratings to infer refractive index and thus the quality of the fuel. A challenge arises as the refractive index of these fuels are typically greater than the refractive index of the waveguide. Therefore, the guided mode operation of FBG refractometers is unsuitable. This work uniquely reports leaky mode operation and a regression analysis, inferring propagation loss through changes in amplitude of successive gratings. In effect, the proposed methodology utilises the imaginary part of the effective index as opposed to the real part, typically used by such sensors. Initial results have shown a 350 (dB/cm)/riu sensitivity is achievable above a refractive index of 1.45. This was measured for a SMF-28 fibre wet etched to 30 µm and planarized. Considering a 0.01 dB/cm propagation loss resolution, refractive index changes of the order 10-5 can be approached. Work will be presented on the fabrication of an IOF platform for refractometers as well as metrics for survivability in harsh environments.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Alan Gray, Alexander Jantzen, Naruo Yoshikawa, Paul C. Gow, Corin B. E. Gawith, Peter G. R. Smith, and Christopher Holmes "An integrated optical fiber device for harsh environment refractometry at indices above silica for monitoring hydrocarbon fuels (Conference Presentation)", Proc. SPIE 10535, Integrated Optics: Devices, Materials, and Technologies XXII, 1053507 (14 March 2018); https://doi.org/10.1117/12.2287728
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KEYWORDS
Refractive index

Integrated optics

Refractometry

Fiber Bragg gratings

Environmental monitoring

Environmental sensing

Fabrication

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