An optical array receiver concept is developed and analyzed. It is shown that for ground-based reception, the number of array elements can be increased without incurring performance degradation, provided the array telescope diameters exceed the coherence-length of the atmosphere. Maximum likelihood detection of turbulence-degraded signal fields is developed for the case of pulse-position modulated signals observed in the presence of background radiation. Performance of optical array receivers is compared to single-aperture receivers with diameters ranging from 4 to 8 m, both in the presence of turbulence and in a turbulence-free environment such as space. It is shown that in the absence of atmospheric turbulence, single-aperture receivers outperform receiver arrays when significant background radiation is present. However, it is also demonstrated that for ground-based reception of deep-space signals, the number of array elements can be as great as several thousand without incurring any performance degradation relative to a large single-aperture receiver.