A dissolved oxygen (DO) sensor based on U-shape plastic optical fiber (POF) and dichlorotris (1, 10-phenanthroline) ruthenium ([Ru(dpp)<sup>3</sup>]<sup>2+</sup>) as an oxygen indicator was described. Fluorescence intensity and lifetime were measured when the sensor was soaked into a water bath blasted with air with varied O<sub>2</sub>/N<sub>2</sub> ratios. The influence of Ru concentration, annealing time and U-shaped POF curve radius on the system sensitivity was also studied. A two-layer model was proposed to analyze the deviation from linear relation described by Stern-Volmer equation, and to explain the deviation and the dependence of the fluorescence on curvature of U-shape POF. By fitting the experimentally measured sub-linear relation of <i>τ</i><sub>0</sub>/<i>τ</i> ratio versus oxygen concentration, the proportion of effectively sensitive layer and the Stern-Volmer coefficient can be evaluated to be <i>f</i>=0.59 and <i>K</i><sub>SV</sub>=0.61 typically.
© 2008 Chinese Optics Letters
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
(130.6010) Integrated optics : Sensors
Fenghong Chu, Haiwen Cai, Ronghui Qu, and Zujie Fang, "Dissolved oxygen sensor by using Ru-fluorescence indicator and a U-shaped plastic optical fiber," Chin. Opt. Lett. 6, 401-404 (2008)