Tunable Diode Laser Absorption Spectroscopy is short for TDLAS. It adopts a specially-made semiconductor laser source, which locks its wavelength to a near-infrared absorption peak of gas, and analyzes the change of optical signal passing through the gas to realize concentration detection. The measured gases include CH₄, NH₃, H₂O, N₂O, O₂, CO, CO₂, H₂S, HCl and some hydrocarbons. Because the absorption peak of gas in the near infrared spectrum is usually very sharp, the measurement is not easily interfered by coexisting gas, and has excellent specificity. Compared with traditional technology, the detection limit and sensitivity have obvious advantages. In addition, TDLAS technology can realize new applications such as remote measurement and distributed optical fiber measurement, which is a promising optical gas detection technology.