Methane concentration measurement using tunable diode laser in near infrared spectrum

The main element for a successful laser-based gas sensing system significantly relies on the availability and performance of tunable laser sources in the measurement spectra. In addition, an appropriate detection scheme should be adopted to obtain a sensitive measurement. Wavelength modulation spectroscopy (WMS) is considered as a sensitive measuring technique in a gas monitoring applications. The paper investigates the experimental results of laser-based methane detection system using WMS technique. Methane absorption lines in near infrared spectrum are targeted using tunable distributed feedback laser (DFB) by modulating the laser current over the absorption lines. Methane concentrations in the range from 0.1% to %5 volume concentration in mixtures with nitrogen as a background gas have been successfully measured.