Communication between cells is instrumental in coordinating population-level activity. In a process known as "quorum sensing," bacteria both secrete and sense autoinducer signaling molecules to enable synchronization of group gene expression paradigms. The synthetic biology community has rapidly adopted these quorum signaling pathways for use in programmed circuitry. However, chemical signals must diffuse between sender and receiver cells, limiting such communication to a common environment. In electronics, when electrical signals must be transferred between two circuits operating at incompatible voltages, electrical engineers use optocouplers, components that transfer information between isolated circuits via light. The 2015 Penn iGEM team presents a biological analog of the optocoupler, a cell-to-cell communication system in which a "sender" cell generates light via bioluminesence and a "receiver" cell expresses photoreceptors to enable light-dependent physiological responses. We show that light elicits a response in light-sensitive receivers and illuminated potential applications for this alternative form of cell communication.