Optical communications in the presence of atmospheric turbulence are affected by the tubulence-induced optical scintillation. The optical scintillation makes the communication quality, i.e. bit error rate (BER), degrade. Because of the intrinsically narrow optical beam, the random pointing-jitter also generates additional signal fading on the communication signal. A broader optical beam could mitigate the signal fading, but would require greater transmitted power than that for the original beam to achieve the same required BER. In this paper, the average BER is derived from the probability density function (PDF) of the optical signal in the presence of atmospheric turbulence and random pointing-jitter. The joint PDF, of the lognormal PDF caused by atmospheric turbulence and the beta PDF of the random pointing-jitter, is derived by using the characteristic function of each PDF. It is shown that an optimum beam divergence of the transmitting laser beam exists, and the optimum value changes slightly with the atmospheric conditions. The beam divergence angle should be about 7 times larger than the random pointing-jitter of the optical tracking system. An example of the optimum link estimates for the tracking and communication channels are shown for a ground-to-satellite optical communication link.