Abstract

Logarithmic-conversion data processing used in wavelength modulation spectroscopy (WMS) with a current-modulated diode laser as its source is analyzed and compared with second-to-first ratio de tection. Analytic Fourier coefficients of logarithmic-converted residual amplitude modulation (RAM) of a light source are given. An experimental setup for methane absorption detection at $1650\mathrm{nm}$ is described. It is shown theoretically and experimentally that logarithmic-converted WMS cannot only eliminate the fluctuation of received light power, but also improve the signal-to-noise ratio significantly.

© 2009 Optical Society of America

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