A novel Photon-Counting Spatial-Diversity-and-Multiplexing (PC-SDM) scheme is proposed for high-speed Free-Space Optical (FSO) transmission over shot-noise limited Poisson channels experiencing turbulence-induced fading. In particular, Iterative Parallel Interference Cancellation (Iter-PIC) aided Q-ary Pulse Position Modulation (Q-PPM) is employed. Simulation results demonstrate that our proposed scheme exhibits a high integrity and a high throughput, while mitigating the effects of multi-stream interference and background radiation noise.