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

Sensors

Qi Zhang¹  Natale J. Ianno¹ 

[1] Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, NE 68588, USA;

关键词: fiber gratings;    optical fiber sensors;    optical resonators;    refractive index;   

DOI  :  10.3390/s130708827

来源: mdpi

【 摘 要 】

We present a compact and highly-sensitive fiber-optic refractometer based on a high-Q π-phase-shifted fiber-Bragg-grating (πFBG) that is chemically etched to the core of the fiber. Due to the π phase-shift, a strong πFBG 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 πFBG 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 πFBG 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.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.