Different methods of obtaining high birefringence in optical fibres are analysed, especially for elliptical core fibre,PANDA type and bow tie fibre. New analytical method of boundary elements /BEM/ has been adopted for strenght component calculation and accuracy of 0,05% in comparision with cylindrical fibre calculation has been obtained. Fibre with elliptical core and elliptical inclusions has been analysed. Three experimental methods for state of polari-zation /SOP/ in the fibre have been developed namely compensation, dynamical and external magnetic field method. Obtained experimental results for different types of fibres are displayed.