Self-Fault Isolation in Transparent p-Cycle Networks: p-Cycles as Their Own m-Cycles

As society grows, our dependence on our communication networks increases. Not only this, but our demands on the network increase. Telecommunication companies have been using optical networks for years to provide the bandwidth we need for the real time communication that keeps our society connected. The body of this bulletin is based on [1].

Two types of optical networks are opaque and transparent. In an opaque network, optical signals are converted to electrical signals at each node. The signal is regenerated and sent optically across a fiber span to the next node. In a transparent network, however, all regeneration and switching is done optically.

One challenge of survivable networking with optically transparent switching is that the failure of a fiber span is not easily and quickly localized to the span at fault. In an opaque network, every optical line signal is electronically processed for switching and failures are inherently identified at the span of origin. However, in an optically transparent network, loss-of-light will propagate along the entire length of the path. Methods are available following the failure to sectionalize the fault, but they are generally slower than required for a protection switching response.

Combining the promising idea of monitoring cycles (or “m-cycles”) for fault localization, proposed and studied by Zeng, Huang, and Vukovich [2][3], with p-cycles, TRLabs has developed a novel idea for fault isolation in optical transparent networks by using p-cycles as m-cycles. This scheme can provide the rapid fault-localization needed to activate p-cycles with little or no extra cost.

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