Fourier Transform Spectrometer (FTS)
Fourier Transform Spectrometer (FTS) is an interferometric spectrometer, which is usually built based on a Michelson interferometer with (at least) one moving mirror and a broadband light source. The moving mirror provides the interference between the two beams at different optical path differences (OPDs). This interference pattern (widely known as “interferogram”) is recorded by a photodetector and the Fourier Transform of the interferogram yields the optical spectrum. In absorption spectroscopy, the sample is placed in the path of the broadband beam, usually before the spectrometer. The transmitted light is sent to the spectrometer and the absorption features of the sample will be visible in the measured optical spectrum.