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Sensors 2013, 13(7), 8827-8834; doi:10.3390/s130708827

Fiber-Optic Refractometer Based on an Etched High-Q π-Phase-Shifted Fiber-Bragg-Grating

Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
* Author to whom correspondence should be addressed.
Received: 28 March 2013 / Revised: 20 May 2013 / Accepted: 2 July 2013 / Published: 10 July 2013
(This article belongs to the Section Physical Sensors)
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We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q p-phase-shifted fiber-Bragg-grating (pFBG) that is chemically etched to the core of the fiber. Due to the p phase-shift, a strong pFBG forms a high-Q optical resonator and the reflection spectrum features an extremely narrow notch that can be used for highly sensitivity refractive index measurement. The etched pFBG demonstrated here has a diameter of ~9.3 μm and a length of only 7 mm, leading to a refractive index responsivity of 2.9 nm/RIU (RIU: refractive index unit) at an ambient refractive index of 1.318. The reflection spectrum of the etched pFBG features an extremely narrow notch with a linewidth of only 2.1 pm in water centered at ~1,550 nm, corresponding to a Q-factor of 7.4 ´ 105, which allows for potentially significantly improved sensitivity over refractometers based on regular fiber Bragg gratings.
Keywords: fiber gratings; optical fiber sensors; optical resonators; refractive index fiber gratings; optical fiber sensors; optical resonators; refractive index
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Zhang, Q.; Ianno, N.J.; Han, M. Fiber-Optic Refractometer Based on an Etched High-Q π-Phase-Shifted Fiber-Bragg-Grating. Sensors 2013, 13, 8827-8834.

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