Abstract
In flexi-grid optical networks, fragmentation of spectrum resources
may significantly affect the overall network efficiency. Effective techniques
for defragmentation (i.e., re-optimization) are then required to limit the
wasting of spectrum resources. However, current defragmentation techniques
can only be implemented thanks to the presence of additional resources, such
as spare expensive transponders. In this study, we propose, discuss and evaluate
a novel defragmentation technique called push-pull. The technique is based
on dynamic lightpath frequency retuning upon proper reconfiguration of allocated
spectrum resources. It does not require additional transponders and does not
determine traffic disruption. All the relevant technological limitations that
may affect the push-pull applicability are discussed in the context of both
optically-amplified direct and coherent detection systems. The technique is
then successfully demonstrated in two different flexi-grid network testbeds,
reproducing the two aforementioned scenarios. In particular, the reoptimization
of a 10 Gb/s OOK lightpath is safely completed in few seconds (mainly due
just to node configuration latencies) without experiencing any traffic disruption.
Similarly, the push-pull is successfully performed on a 100 Gb/s PM-QPSK lightpath,
providing no traffic disruption.
© 2012 IEEE
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