KEYWORDS: Sensors, Fiber optics sensors, Absorption, Cladding, Active remote sensing, Fiber optics, Signal attenuation, Optical fibers, Refraction, Chemical species
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.
This paper reports the development of a hydrazine fiber optic reversible sensor that operates, for the first time to our
knowledge, in the lowest attenuation wavelength range of commercial silica fibers. A pentacenediquinone (PDQ) and
polymer mix, with an index of refraction adjusted to closely match that of silica, was used as an active sensing material
replacing the cladding of a silica core optical fiber. The optical signal passing through this modified cladding type fiber
sensor exhibited a reversible intensity change in the presence hydrazine at different concentrations.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.