In this letter, we investigate the performance of a coherent free-space optical (FSO) communication system with multiple receive apertures over atmospheric turbulence fading channels. In particular, we derive the average error probability and the ergodic capacity of the coherent FSO system with multiple receive apertures in series representations. To mitigate the atmospheric turbulence-induced amplitude fluctuations and phase aberrations, we use, at the receive apertures, the modal compensation technique. Numerical results confirm the derived average error probability and ergodic capacity expressions.