A Novel Fiber CAN Hub and Its Networking Schemes

The overall behavior of some twisted-pair CAN systems may be improved by use of optical fiber as physical medium. In this paper, a novel fiber CAN hub and the schemes of constructing CAN network based on it are proposed. The working principle of the hub is discussed in detail. WDM (Wavelength Division Multiplexing) technology is utilized to realize duplex signal transmission on one fiber link. By replacing the “Wired-AND” in twisted-pair CAN bus with the logic “AND” in CPLD (Complex Programmable Logic Device) and ensuring each node's bus monitoring function by sending the “ANDed” signal back, the fiber CAN network thus formed is fully compatible with the CAN standard above physical layer. Methods of expanding fiber CAN network are also discussed. An eight-port prototype hub is implemented and tested to prove the feasibility and practicability of the proposed schemes. Features of the fiber CAN network are summarized and future works are pointed out.