Within the past 15 years there has been significant progress in the development of two-dimensional arrays of optical and optoelectronic devices. This progress has, in turn, led to the construction of several free-space digital optical system demonstrators. The first was an optical master-slave flip-flop using Hughes liquid-crystal light valves as optical logic gates and computer-generated holograms as the gate-to-gate interconnects. This was demonstrated at USC in 1984. Since then there have been numerous demonstrations of free-space digital optical systems including a simple optical computing system (1990) and five switching fabrics designated System/sub 1/ (1988), System/sub 2/ (1989), System/sub 3/ (1990), System/sub 4/ (1991) and System/sub 5/ (1993). The main focus of this paper will be to describe the five switching fabric demonstrators constructed by AT&T in Naperville, IL. The paper will begin with an overview of the SEED technology which was the device platform used by the demonstrators. This will be followed by a discussion of the architecture, optics, and optomechanics developed for each of the five demonstrators.>