Liquid crystal modulators are optical components that can be used in free-space optical communication. FOI has been studying this technique for some years and has developed a new generation of modulators in co-operation with Chalmers University of Technology. To make the most of them it is important to know their optical and electrical properties. The modulators consist of a thin ferroelectric liquid crystal layer between two ITO surfaces and modulate the polarisation of the radiation by means of their birefringence. The unique axis of the liquid crystal can be steered by an electric voltage over the ITO surfaces. The angle of the axis depends on several factors like temperature, voltage and frequency. The voltage is in turn influenced by the resistances and capacitances of the modulator. An experimental set-up at FOI has been used for measuring the optic and electric properties. Models have been developed in the mathematics program Matlab for analyse of measurement data and simulation of the modulators. The angle of the unique axis has been determined at various temperatures and to some degree frequencies. The variation of signal strength has been measured as a function of temperature, voltage and frequency, and the bandwidth has been studied. The bandwidth was notably larger in the new generation of modulators.