An in-line fibre-optic polarising beam splitter, consisting of a fused birefringent-fibre coupler, is reported. Splitting of the orthogonally polarised lights was accomplished by increasing the difference of coupling ratios for the two polarisation modes. When a light at 1.402 μm wavelength was coupled to the input lead, each polarisation was split on to different output leads, showing extinction ratios of more than 17 dB in both leads.