Detection of gas temperature using a distributed feedback laser at O_2 absorption wavelength 760 nm

Direct absorption spectroscopy for gas temperature monitoring in a tube furnace is proposed over the temperature range 300–900 K with intervals of 100 K. This detecting technique is based on the relationship between two lines’ absorption strength and temperature. The gas temperature can be inferred from the ratio of the integrated spectral area of the oxygen absorption features measured with a distributed feedback diode laser near 760 nm. Compared with the thermocouple measured results, the direct absorption spectroscopy approach also provides a temporal resolution. The results show that the accuracy is better at low temperatures than at high temperatures. In the future, we hope to improve the detection accuracy and demonstrate the utility of the diode laser absorption sensors operating for active combustion diagnostics and optimizations, simultaneously.