A natural gas leakage detector based on scanned-wavelength direct absorption spectroscopy is described. The sensor employs a multi-channel scanned-wavelength direct absorption strategy. It has the potential to simultaneously monitor methane and hydrogen sulfide in open path environment. Traditionally, scanned wavelength direct absorption spectroscopy is the technique choice for natural gas leakage applications because of its simplicity, accuracy, and stability. We perform the gas sensor using direct-absorption wavelength scans with isolated features at 1-kHz repetition rate and the center wavelength is stabilized at the center of the 2 \nu 3 band R(3) line of methane (1.65 \mu m) and the (\nu 1 +\nu 2 +\nu 3) combination band of hydrogen sulfide (1.57 \mu m), respectively. The influence of light intensity fluctuations can be eliminated by using scanned-wavelength direct absorption spectroscopy. Because of the fast wavelength scanning, the sensor has a response time of less than 0.1 s. The sensor can be configured to sense leakages in path-integrated concentrations of, for example, 100-ppm·m hydrogen sulfide and 10-ppm·m methane.
© 2010 Chinese Optics LettersPDF Article