Electrically tuneable micromachined fabry-perot interferometer in gas analysis

This paper describes an optical gas concentration measurement system, which is based on an electrically tuneable micromachined Fabry-Perot interferometer (FPI). The operating principle of the system is NDIR Single-Beam Dual-Wavelength measurement. The FPI is tuned so that the pass band coincides with the absorption band of the measured gas; a detector records the strength of the signal getting through the measurement chamber. The pass band of the FPI is then shifted to either side of the absorption band; the detected signal constitutes the reference signal. The ratio of these two signals indicates the degree of light absorption and so the gas concentration. Properties of the FPI are discussed, as well as the performance of the measurement system.