We present a comprehensive model of a CO2 correlation spectroscopy based gas sensor. Predictions of the sensor response for typical fiber optic-coupled systems are made, taking into account effects of noise in detected signals.
Monitoring the concentration of gaseous O2, CO2 and CH4 is needed for many environmental, medical and industrial applications. We model the COSM method of correlation spectroscopy, where two broadband light sources are intensity modulated in antiphase, the first being directed via the measurement cell after first passing through the reference sample, the second being more directly-coupled. The subsequent difference in fractional attenuation in the measurement cell indicates the concentration of target gas in this cell. Using data from the HITRAN database, comprehensive analyses are presented to predict the optical modulation index and the signal to noise ratio at the detector, as a function of optical filter properties, and for various gas temperatures and pressures (concentrations). The predicted detection sensitivities are presented for each gas.