The present invention is related to a Fourier-transform spectrometer arrangement comprising a first polarizer, a birefringent plate, a pair of birefringent wedges, a second polarizer, a photo detector, and a control unit. According to the invention, the cross sections of the two birefringent wedges of the birefringent wedge pair are similar triangles, the first wedge is fixed, the second wedge is capable of linearly movement along the side, the optic axes of the pair of birefringent wedges are parallel to each other and orthogonal to the optic axis of the birefringent plate, the polarization of the first polarizer is in 45 degrees with the optical axis of the birefringent plate, the polarization of the first polarizer is also in 45 degrees with the optical axis of the pair of birefringent wedges, the polarization of the second polarizer is parallel, or orthogonal, to the polarization of the first polarizer.