We have studied, assembled, and tested several different types of phase-modulated optical polarimeters capable of transient stress and molecular orientation angle measurements in complex optically anisotropic fluids and materials. The main difference in the instrumentation lies in the applied modulation technique. Three different phase modulation techniques are studied in this paper: the photoelastic effect, the transverse electro-optic effect, and liquid-crystal variable retardation modulation schemes. The precise measurement of a material's retardance and average molecular orientation angle depends on an accurate alignment and calibration within the range of the chosen modulator. Therefore, we address some of the issues associated with the choice of phase modulator as well as applicable alignment and calibration techniques. We also study and test several methods that may be used to ameliorate these issues.