Dynamic Light Trail Routing in WDM Optical Networks


Fiber optics have replaced copper as the primary transmission medium. Wavelength Division Multiplexing (WDM) networks effectively increase single-link bandwidth from 10Mbps to over 160Gbps, and have been considered as a promising candidate for the next-generation backbone network. All optical circuits each on a separate wavelength called lightpaths represent the first major method for optical communication. The granularity provided between a source and destination node is that of a complete wavelength. Once a lightpath is set up, the entire wavelength is used exclusively by the connection’s source and destination node-pair. No sub-wavelength sharing between nodes along the lightpath is allowed. However, it is often observed that the bandwidth requirement in today’s network is often dynamically varying and does not justify the need for allocating an entire wavelength. Therefore, the wavelength capacity may be underutilized. A new technology termed light trail was proposed to avoid the inability of intermediate nodes to use a connection wavelength, and the constant reconfiguration of switches. In this paper, we study dynamic light trail routing in a WDM optical network. We present an efficient algorithm for establishing a light trail routing for a new connection request, while using minimum network resources. We also study survivable network routing using the proposed light trail technology. We present an efficient heuristic for computing a pair of working and protection light trails for a dynamic incoming connection request. Simulation results are presented which demonstrate the advantages of our routing schemes.

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