Wavelength modulation spectroscopy method and system

摘要

In a wavelength modulation spectroscopy method and system the wavelength of a light source is modulated with a frequency f₀. The light of the light source is passed to a sample for interacting and thereafter detected and demodulated at a higher harmonic Nf₀. To suppress non-linearities in the modulation of the wavelength of the light source a portion of the light ( 15 ) of the light source ( 14 ) is passed to a monitor detector ( 17 ). The monitor detector output is demodulated at said higher harmonic Nf₀, and the modulation of the light source ( 14 ) is predistorted at said higher harmonic Nf₀ in dependence on said demodulated monitor detector output.