In this paper, the performance of binary polarisation shift keying (BPOLSK) with the direct detection (DD) scheme is experimentally investigated. BPOLSK scheme is used to mitigate the atmospheric turbulence induced fading in a free space optical (FSO) communication link. For comparison the experimental and analytical results for the non-return-to-zero on-off keying (NRZ-OOK) have also been presented. The experimental Q-factors are verified in conjunction with theoretical values in weak turbulence regime to confirm the validity of the proposed scheme. The results have shown that BPOLSK offers higher Q-factor values compared to NRZ-OOK for the same transmitted optical power and the turbulence variance. For example, when the turbulence variance σ2l is 0.03, the Q-factors are 4.6 and 5 for NRZ-OOK and BPOLSK respectively.