A Compact Noise-Immune TDLAS Temperature Sensor using Intensity Modulation

In this paper, a noise-immune method with light intensity modulation was proposed by using a Mach-Zehnder fiber interferometer. Meanwhile, the fiber interferometer was reused as an etalon to make the sensor configuration more compact. Compared with direct absorption spectroscopy (DAS), the optical path for measuring the absorption spectrum and the optical path for measuring wavenumber were combined. It combined the advantages of measuring the absolute absorbance profile from the DAS method with noise suppression ability of the amplitude modulation. Experiments showed that the new method is more robust than the DAS method in case of background light interference. It provided a new way to detect the actual temperature in a harsh environment, such as backgrounds interrupted by fluctuating thermal radiations.