17 May 2011 Hydrazine concentration fiber optic reversible sensor
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Proceedings Volume 7753, 21st International Conference on Optical Fiber Sensors; 77535A (2011); doi: 10.1117/12.886074
Event: 21st International Conference on Optical Fibre Sensors (OFS21), 2011, Ottawa, Canada
Abstract
This paper reports the development of a reversible fiber optic leak sensor capable of detecting the presence and the concentration of traces of hydrazine. The sensor operates in the lowest attenuation wavelength range of commercial silica fibers. The sensing material utilized in this sensor is a mix of organic compounds that contains pentacenediquinone (PDQ) as an active sensing element. The index of refraction of this mix is adjusted to closely match that of fiber's silica core. In the absence of hydrazine this mix exhibits a weak absorption in the near-infrared. When the PDQ reacts with hydrazine, oxygen atoms from the PDQ are replaced by a molecule of hydrazine resulting in water as a by-product. This replacement significantly increases the absorption of the mix specifically at wavelength between 1310 and 1430 nm. This absorption was found to be proportional to hydrazine gas concentration. The reaction however is a self-reversible i.e. in the presence of water; the by-products of the reverse reaction would be PDQ and hydrazine. A modified cladding fiber sensor was fabricated by replacing part of cladding with the PDQ sensing mix. Due to evanescence-wave absorption by the modified sensing cladding, the optical signal passing through this sensor exhibited a reversible intensity change in the presence hydrazine at different concentrations. Sensor's percentage response magnitude and response time were found to be proportional to HZ gas concentration. Hence, in addition to low loss operating wavelength advantage, this sensor is capable not only to detect HZ presence of but also its concentration.
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Alfred Andrawis, Yuelin Peng, XingZhong Yan, Barun Ranjitkar, "Hydrazine concentration fiber optic reversible sensor", Proc. SPIE 7753, 21st International Conference on Optical Fiber Sensors, 77535A (17 May 2011); doi: 10.1117/12.886074; https://doi.org/10.1117/12.886074
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KEYWORDS
Sensors

Fiber optics sensors

Absorption

Cladding

Active remote sensing

Fiber optics

Signal attenuation

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