Optical logic circuits: a new approach to the control of fiber optic LANs

The centralized filtering of the transmitted packets has been the base of a family of high-performance protocols for WDM star networks. Protocols of this family have been proved to achieve a significantly higher performance than the well-known contention-oriented or round-robin protocols. However, the need for electronic control of the filtering mechanism as well as the use of slowly tunable acoustooptic filters have been limiting factors in their performance. Furthermore, since the network hub of WDM star networks represents a single point of failure, the extensive use of electronic circuits at this point reduces the reliability of the system. In this paper, an all-optical centralized protocol is introduced. According to this protocol, the passing of the transmitted packets to the star coupler is controlled by means of optical logic circuits, without the need of optical to electronic translation or electronic processing of the network feedback information. In this way, the processing time is drastically reduced, while the need for acoustooptic filters is eliminated. Therefore, a significant performance improvement is achieved. Furthermore, due to the all-optical nature of the network hub, the reliability of the system is improved. The performance of the proposed protocol is studied via extensive analytical and simulation results which indicate that a WDM star network operating under this protocol achieves a high throughput-delay performance under any load conditions.