PROCEEDINGS ARTICLE | November 30, 2011
Proc. SPIE. 8201, 2011 International Conference on Optical Instruments and Technology: Optoelectronic Measurement Technology and Systems
KEYWORDS: Fabry–Perot interferometers, Methane, Optical amplifiers, LabVIEW, Fiber lasers, Data acquisition, Attenuators, Gas lasers, Sensing systems, Absorption
Detection of pollution, inflammable, explosive gases such as methane, acetylene, carbon monoxide and so on is very
important for many areas, such as environmental, mining and petrochemical industry. Intra-cavity gas absorption sensing
technique (ICGAST) based on Erbium-doped fiber ring laser (EDFRL) is one of novel methods for trace gas with higher
precision. It has attracted considerable attention, and many research institutes focus on it. Instrumentation and
optimization of ICGAST was reported in this paper. The system consists of five parts, which are variable gain module,
intelligent frequency-selection module, gas cell, DAQ module and computer respectively. Variable gain module and
intelligent frequency-selection module are combined to establish the intra-cavity of the ring laser. Gas cell is used as gas
sensor. DAQ module is used to realize data acquisition synchronously. And gas demodulation is finished in the computer
finally. The system was optimized by adjusting the sequence of the components. Take experimental simulation as an example, the absorptance of gas was increased five times after optimization, and the sensitivity enhancement factor can reach more than twenty. By using Fabry-Perot (F-P) etalon, the absorption wavelength of the detected gas can be obtained, with error less than 20 pm. The spectra of the detected gas can be swept continuously to obtain several absorption lines in one loop. The coefficient of variation (CV) was used to show the repeatability of gas concentration detection. And results of CV value can be less than 0.014.
