The fabrication and characterization of an optical fiber oxygen sensor based on oxygen fluorescence quenching are described. The sensors are prepared by coating the oxygen sensitive indicator (tris-BP ruthenium (II) chloride and platinum octaethylporphyrin) that is immobilized by the sol-gel route onto the uncladded middle portion of a multimode plastic optical fiber. A design of experiment based on two parameters which are the uncladded coated length and withdrawal rate was carried out in order to identify the optimum setting that gives the highest fluorescence emission which leads to better sensitivity. The sensitivity of the optical oxygen sensor is quantified in terms of the ratio I0/I where I0 and I represent the fluorescence intensities in pure nitrogen and pure oxygen environments, respectively. Both ruthenium and platinum coated fiber produced a linear Stern-Volmer relationship which indicate the homogeneous environment of the luminophore. The experimental result reveals that the optimized setting for ruthenium sol-gel coated fiber is 5 mm decladded length and 120 mm/min withdrawal rate while for platinum sol-gel coated fiber is 8 mm decladded length and 160 mm/min withdrawal rate.