Polarization mode dispersion (PMD) causes pulse broadening and power fading of the received signal in optical fiber transmission. Most research uses the waveplate model in mimicking first-order PMD effects on optical fiber links. However, the waveplate model is only capable of providing static PMD effects. The thesis propose a method to provide time varying effects into the waveplate model, by applying Brownian motion properties to the appropriate parameters in the waveplate model. This provides the means to investigate PMD effects in more extreme cases, such as changes of PMD effects due to changes in temperature at different periods of time. The thesis also investigates the performance of the proposed time varying model compared to the original waveplate model.