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By providing several parallel high-capacity channels in the same fiber, WDM technology is commonly considered to be one of the fundamental solutions for future high speed computer networks. By means of WDM the potential THz bandwidth of the optical fiber can be multiplexed into channels with transmission speed compatible with opto/electronic and electro/optic converters -- e.g., transmitters and receivers. However, a fundamental scalability problem has to be solved in order to build larger than LAN size WDM packet switched all- optical networks. Current solutions can not be scaled by simply adding nodes to the existing system due to the limited number of wavelengths and/or the available power budget. The lack of modular solutions, similar to those used in traditional electronic networks, can be attributed to the unavailability of optical technology that can support switching of WDM channels on a per packet basis. Recently, a novel approach was proposed to obtain a packet switching WDM network which is scalable in coverage area, size and number of wavelengths. The approach is based on the combination of two ideas -- use of a backbone that connects (bridges) multiple LAN segments, where bridging is done using the new concept of photonic slot routing (PSR). In this concept, packets transmitted simultaneously on the WDM channels in any 'photonic' slot are switched jointly in the bridge between the LAN segments and the backbone. Thus packets in a given slot remain transmitted on the same path, from their source LAN to the destination LAN and consequently, the bridge is only required to handle complete slots, i.e., all WDM channels jointly. The aim of this work is to present the first analytical model developed to evaluate the performance of the photonic slot concept applied to a single fiber ring backbone system, independently on the interconnected LAN segment topologies, e.g., ring, folded bus, star.
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