?– EPONs are based on highly cost-effective components, where relaxed hardware
requirements and increased guard-bands both in downstream and upstream channels
allow for application of lower grade lasers and receiver modules with wider
176 Chapter 7
quality margins. A number of choices, in terms of EPON physical layer (PHY)
parameters, have allowed this type of PON system to become one of the most promising
solutions, as far as cost and service delivery are concerned. Native support
for Ethernet framing and re-use of existing 1 Gbps Ethernet MAC chipsets, as well
as the dramatically increasing number of deployed Ethernet ports, make EPONs a
technology of choice for interconnecting Ethernet-based LANs, SANs, or other types
of Ethernet-based networks.
?– EPON systems are agnostic as far as transported data format is concerned. Recent
add-ons to the generic Ethernet technology, in terms of pseudo-wire emulation,
standard telecommunications quality of service (QoS) measures, VLAN tagging,
and transmission system protection mechanisms, allow current EPONs to deliver
any type of data (including digitized voice, video, etc.) with full QoS support, using
a single framing format that perhaps has proven to be not the most efficient, as
far as encapsulation overhead is concerned, but definitely the most robust among
other existing data packet transmission protocols.
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