Atmospheric turbulence is the main impairment in free space optical communication links. To mitigate the effect of turbulence spatial diversity techniques are used. In this paper, we analyse the performance of Gamma-Gamma channel model with spatial diversity and compare it with K-distribution. The modulation techniques assumed here are on-off keying, binary PPM and binary phase shift keying and the bit error rate and Gain performance with single input single output (SISO), single input multiple output(SIMO), multiple input single output (MISO) and multiple input multiple output (MIMO) are presented.