We propose and demonstrate an adaptive quality of transmission (QoT) restoration scheme combining the methods of lightpath rerouting and modulation-format switching to overcome real-time impairments in elastic optical networks. A hybrid objective algorithm is designed to minimize the spectral consumption and the interference that the rerouting imposes on the other parts of the network. Simulation results show the algorithm achieved more than 50% reduction in blocking probability and 75% decrease in the spectral consumption on the bypass links compared with the rerouting-only method. Testbed experiments demonstrated successful real-time QoT restoration in the presence of time-varying optical signal-to-noise ratio impairment for two simultaneously impaired 100 and 200 Gb/s quaternary phase-shift keying superchannels.
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