Specifically, EPL rate changes will only require edge interface
(transponder) upgrades and possibly selected changes to amplifier and dispersion
module placements. This contrasts with EoS or EoMPLS, which require comprehensive
node upgrades throughout the network to run increased interface speeds. Optical
transparency also enables full-rate EoWDM services to co-exist with other network implementations
over the same fiber-plant (EoS, EoMPLS, and even legacy TDM private
line). This is of crucial importance to incumbents since it allows them to complement
subrate EoS systems and achieve staged, timely migrations. Finally, the physical-layer
separation of WDM channels ensures high-security/confidentiality between clients.
As mentioned earlier, EoWDM replicates ???five nines??? resiliency and sub-50ms recovery.
Although EoS and EoRPR can also achieve these bounds, their switchover capacities
are much more limited. For example, DWDM-layer protection can restore well over
a hundred 10 Gbps EPL connections in one span switch. However, EoWDM recovery
is very coarse, and hence, carriers may have to perform some form of higher-layer
grooming to achieve service selectivity.
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