A new fiber optic oxygen sensor based on the fluorescence quenching of Ru(phen)3Cl2 has been fabricated by thermo-polymerization method. The ruthenium dye is immobilized in N,V-methylene bisacrylamide (MBBA) polymer by physically trapping while MBBA is covalently cross-linked on the glass micro-pearls by NaHSO_3-O_2-MnSO_4 initiator system. The immobilization stability of ruthenium dye and performance of the sensor are improved by the new polymerization system. The polymerization reactivity is enhanced by optimizing the concentration of NaHSO_3, MnSO_4, MBBA, Ru(phen)3Cl2 and the best diameter of the glass micro-pearls. An absolute detection limit of 5* 10~(-6) (V/V) and the response time of 10 s can be achieved. The sensor is fully reversible and highly reproducible. The standard deviation of around ± 1 % within 50 min consecutive measurements has been observed for various oxygen concentrations.

Key words: SENSORS, OXYGEN, FLUORESCENCE QUENCHER, CROSSLINKING, OPTICAL FIBER, PROPENAMIDE P, PHENANTHROLINE, RUTHENIUM COMPLEX