Nevertheless, a strong consensus exists in the group regarding the following
issues:
?– coexistence is mandatory to assure smooth transition path from 1 Gbps to 10 Gbps
equipment and to avoid a significant one time investment into such a cost-sensitive
market (CAPEX);
?– wavelength allocation plan for 10 Gbps EPON systems must take into account
existence of 1 Gbps equipment on the same PON plant for both downstream and
upstream channels;
?– the said wavelength allocation plan must also account for the existence of a downstream
analog video delivery service, which will most likely be maintained in the
future 10G EPON systems, mainly due to already existing equipment and significant
CAPEX investment;
?– due to incompatible data rates (1 Gbps EPONs use 8B/10B encoding increasing
the data rate to 1.25 Gbps while 10 Gbps EPONs will most likely use 64B/66B
encoding with PMD level data rate of 10.3125 Gbps), the downstream channels
for the two EPON systems will be WDM multiplexed, with 1 Gbps using 1490 nm
?± 10 nm window and the 10 Gbps using a currently undefined window, allocated
between 1500 and 1600 nm, depending on the laser availability, power budget,
Passive Optical Networks (PONs) 187
ONU triplexer design, filter requirements, and so on.
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