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We have developed a high speed vehicle communication network, that can be used in the real time control of ECU'S (Electronic Control Units: for example anti-lock brake systems, traction control systems etc.). This network is constructed using 6 Mbps optical links, an 8*8 passive type star coupler and access controller. Each node access in this system is controlled by the token bus method. The access controller in each node was originally designed for this network. The results of the operating test have shown that the maximum data communication time from node to node is only 300 μ s. This network has been designed so that the breakdown of any one node does not affect the other 7 nodes, and we have confirmed that this recovery system works well.

Fiber-optic data links have been developed for use in vehicle navigation systems, especially for the communication of CD data. The links consist of transmitters, receivers, and cable assemblies. The transmitters, which include only LEDs, must have driver circuits on their exteriors. In the receiver section, a PD, an amplifier, and a TTL compatible comparator are all integrated into the custom designed IC which is hermetically sealed into an originally developed metal package. Small optical connectors and heat-resistant plastic fiber cords with sufficient reliability and good operability for automotive uses have also been developed.

An optical receiver IC for fiber-optic data links has been developed for use in multiplex wiring harnesses. This IC consists of a PD (Photodiode), a transimpedance, an amplifier, and a comparator to be compatible with TTL. A PD and these circuits are all integrated into one chip, the size of which is 3 mm square, by using the Si-bipolar process. It is hermetically sealed in a can package. It operates at a data rate up to 1 Mbps (Mbps = 106 bits per second). It also has no requirement of sensitivity adjustment for its wide dynamic range (25 dB).