Transmission characteristics of free-space optical (FSO) data transmission systems are characterized. Issues of optical directionality, being related to the optical modulation depth, are investigated for a variety of retroreflecting structures. A composite solid retroreflector is introduced as a novel element for such optical wireless systems, and it is shown that this device has an omni-directional retroreflective angular response covering the full 4Πsteradians solid angle. Such a configuration is a particularly intriguing solution for point-to-point and line-of-sight (LOS) optical communication implementations, and these dynamic modulation characteristics are investigated