Theory and Instrumentation of Fourier Transform Spectroscopy

Fourier transform spectroscopy (FTS) has been widely used as an analytical tool for many applications in science and engineering. In this paper, we describe the operation principle and practical implementation of an FTS prototype. First, the structure of an FTS setup based on optical interferometers is introduced, and its optical and electronic components are identified. A simple theory is presented to show the Fourier transform relationship between the measured interferogarm signal at the detector and the spectral intensity of the source. Then, simulation results based on ray-tracing method are demonstrated to show the effect of coherent length of the source on the spectral intensity. Finally, various practical considerations to implement an FTS setup including noise/interference reduction are discussed, and the effect of alignment on the measurement accuracy is investigated. Since the design and implementation of an FTS measurement setup requires the knowledge from various parts of physics and engineering education, therefore, we believe that FTS can provide a very comprehensive educational tool for the last year undergraduate and graduate students.