This paper proposes a next-generation optical access architecture supporting machine-to-machine (M2M) communication in large-scale sensor-actuator networks. Especially, in this paper, we focus on a smart grid system, which is an application of the large-scale sensor-actuator networks. As a communication infrastructure in the smart grid, optical communication has many advantages over other communication technologies such as wireless communication and power line communication. However, the current optical access systems, e.g. Ethernet passive optical network (EPON) systems, cannot satisfy all requirements for the smart grid communication. In this research, some applicable optical access technologies are discussed from the viewpoint of capacity, reliability, security, energy efficiency and so on. In addition, the existing power-saving mechanism for EPON systems is evaluated using M2M traffic. The proposed architecture can be applied to a communication system in future smart communities including the smart grid, intelligent transport systems and other Internet services.