Real-time Ethernet based on passive optical networks

A passive optical network (PON) based real-time Ethernet (PONRTE), which can take advantage of PON features such as broad bandwidth, high reliability, and easy maintenance to satisfy the determination and real-time requirements of high performance industrial applications, is proposed. The protocol model and network architecture having a compatible physical layer and MAC layer with Ethernet passive optical network are presented for the proposed PONRTE. A fixed periodic time slot allocation mechanism including a synchronic time division multiplexing transmission and an asynchronic data transmission is adopted to guarantee the determination and real-time of the communication. A simple and easy to implement time synchronization approach, where the starting time of the first transmission slot of an access node is synchronized by a relative time synchronization while the starting time of subsequent slots is determined by the fixed period and a dynamic time synchronization, is designed to support the fixed time slot allocation mechanism and avoid the collision in PONRTE. A 100 Mb/s PONRTE experimental testbed with 16 access nodes and a time allocation period of 240 mu s is demonstrated. The results show that the experimental PONRTE can work stably and reliably with a frame loss ratio less than 10(-7). (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.52.2.025007]