Gigabit in-vehicle communication systems using AGF-harness

July 31, 2014 // By Hayato Yuki et al., Sumitomo
This paper focuses on comparisons of transmission characteristics between the Expanded-beam optics method (EBO) introduced by MOSTCO and the Direct coupling method (Butt-coupling) which is the proposed method by Sumitomo. AGF (All Glass Fiber) is used as a transmission medium for both methods. This paper discusses the comparison of two methods mentioned above.

Compared to Butt-coupling, it has been found that EBO exhibits higher insertion loss and significant manufacturing variations due to a large optical-coupling area, regardless of the sufficient tolerance against the dust. The next generation MOST system requires the gigabit communication. In the case of EBO, it was revealed that the performance capabilities of the fiber optic transceiver (FOT) are limited and the allowable loss-budget for the optical harness decreases significantly. The butt-coupling method has a proven optical stability and reliability. However, automakers have pointed out the inadequacies of dust tolerance although Butt-coupling meets all the requirements of vehicle environmental testing.

In this study, Sumitomo carried out an experiment to compare the dust tolerance of optical harness connectors on experimental data gathered from several optical coupling methods. The experiment verified the assumption that the feasibility of a high-speed communication system and dust tolerance could be improved. Thus, Sumitomo introduces their approach toward the realization of gigabit communication that remains very stable under the severe environmental conditions of vehicles. The experiment will hopefully contribute to further development of automotive high speed communication systems.

Improvement of environmental tolerance characteristics

Automotive components require high reliability and durability to withstand dense humidity, higher/lower temperatures, contaminants or external forces under severe stress exposure. In a particular use, strict requirements have been established which are intended for testing under the combined environmental stress of vehicles. Because the AGF-based optical harness had never been adopted for automotive use, comprehensive evaluations for environmental tolerance were required. There are no significant differences in methods and requirements for evaluations of the environmental tolerance in different countries although evaluation standards vary from country to country according to the automotive environmental conditions. At the MOST Forum 2013, Sumitomo reported that the AGF solution has been developed by Sumitomo to meet IEEE and European standards.

However, some issues and problems were addressed concerning the use of specialized components called “AGF”. For AGF, thin optical

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