Abstract

In this paper we describe an open-air long-distance CO2 monitor that is based on Tunable Diode laser Frequency Modulation Spectroscopy. Traditionally, FM spectroscopy employs phase sensitive homodyne detection, i.e. the DC output depends on the phase ϕ between the detected modulation signal and the local oscillator. The presence of turbulence in the optical path of the instrument leads not only to fluctuations of detected laser power but also to fluctuations of phase [1,2,3].

© 2006 Optical Society of America