Effective suppression of transient-induced impairments in transparent optical networks

In transparent networks, fiber cuts can generate severe penalties: Sudden disappearing of channels in one lightpath may affect channels on joint lightpaths and even channels in disjoint lightpaths. We propose a simple and cost-effective scheme that is able to fully suppress these power transients in a realistic network environment. Using the symmetric counter-propagating wavelength-division-multiplexing (WDM) signals, the missing channels can be effectively replaced. In the experiments, we obtained a very short replacement time, complete suppression of any power transient, and full recovery of system penalty in joint and disjoint lightpaths. The scheme was found to be also robust to power unbalance and spectral difference between the missing and replacement WDM signals.