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Restoration mechanisms based on tunable lasers for handling channel and link failures in optical WDM networks

In this paper, we study restoration mechanisms to handle channel and link failures in an optical WDM wavelength-routed wide-area backbone network based on a mesh topology. The solution uses a small number of tunable lasers per link to provide restoration capability. In addition to link failures, we consider individual channel failures link-level mechanisms are presented: redirection algorithm (RDA) and disjoint path algorithm (DPA). These mechanisms use WDM-specific link information to compute the link restoration routes. We present results based on discrete-event simulations to understand the performance of the proposed mechanisms, in terms of restoration efficiency and restoration times. The results show that for networks of varying size and node degree with 32 wavelengths on each link, using as few as 8 tunable lasers per link provides good restoration efficiency under moderate traffic load. which might occur when one or more transceivers fail at the source of the lightpath or due to a failure in the switch fabric. Restoration is first attempted using the tunable lasers to transmit on the failed wavelengths. If all the failed lightpaths cannot be restored using the tunable lasers, unused wavelengths on the same link are used (this requires optical wavelength conversion at the nodes). For the remaining lightpaths requiring restoration, link-level restoration mechanisms are attempted. Two different