The construction and performance of a Fourier transform spectrometer designed for the far infrared spectroscopy is described. The spectrometer has a combined optics of Michelson's and Martin -Puplett's. Some cooled high sensitive semiconducting detectors are used. Gaseous absorption spectra and the optical constants of dielectrics including some new materials have been measured and the results are presented. Resolution of 0.03 cm-1 and accuracy of wavenumber within ±0.001cm-1 are obtained.
