Although the title of this special issue suggests a dichotomy between systems which compute in optics and systems which communicate in optics, this distinction is not as clear as it may seem. Optical computing generally suggests free space systems in which the output of laser arrays is directed by physical optics through spatial light modulators and then to arrays of detectors. Optical interconnections suggest optical or electro-optical networks consisting of switched channels in the time, space, or wavelength domain. Yet, fundamentally, all of these systems face the same challenge of reconciling the high bandwidth of optics with a relatively slow control speed. Specifically, a fundamental aspect of modern digital systems is the concept of state. The use of feedback signals allows for the recording of the state history and thus permits decisions to be made based on that history. Feedback represents a direct interaction of data signals with control signals. Although such an interaction is very common in electronic circuits, its implementation in purely photonic systems is rather difficult because of the absence of fast and efficient optically controlled photonic switches.