Paramagnetic oxygen measurement using an optical-fiber microphone

The oxygen molecule has a strong paramagnetic property compared with other gases. Several methods have been developed to detect oxygen concentration in the air based on this property. In this study, an alternative magnetic field was used to generate an acoustic air pressure signal. This pressure signal is proportional to oxygen concentration in the air, and it is treated as an index of oxygen concentration. To prevent interference of magnetic field on the air pressure sensor, an optical-fiber microphone was used to detect the magneto-acoustic signal. This measurement system was calibrated by gas samples with known oxygen concentrations, and the correlation coefficient of calibration is over 0.99. Mainstream measurement could be possible by using this type of sensing probe.