Phase 1: GPON
Phase 3: adding XGS-PON
Phase 2: GPON full capacity
Phase 4: fully upgraded
2.5G DS/1.25G US
2.5G DS/1.25G US
time-domain reflectometer (OTDR) measurements can be performed in-band
without service interruption.
Ratified as part of IEEE 802.3’s Ethernet
in the First Mile project, 1G EPON is a
1-Gbit/sec Ethernet passive optical network
standard. The 10G EPON standard was
also developed to support 10G/10G symmetric downstream and upstream speed.
Currently, the IEEE 802.3ca task force
is working on 25G/50G/100G EPON standards development. All EPON standards
are developed to be backward and forward compatible to support legacy service and new higher-speed service over
the same ODN.
Radio frequency over glass (RFoG) network design was developed by the Society
of Cable Telecommunications Engineers
(SCTE) under IPS 910 and later became
Mainly deployed in North America,
backward compatibility with RFoG is
also required in some PON deployments
Different PON systems can overlay on the same ODN with a CEx that
supports PON system forward/back-ward compatibility.
• Multiple OLTs of different generations
and service types can be overlaid over
the same fiber.
• In the downstream, signals from multiple OLTs are combined at CEx and
simultaneously sent to the ONT side.
Each ON T receives its signal with a
wavelength filter in the optical module. ON Ts also have wavelength
block filters (WBF) to block future
• In the upstream, wavelengths from different ON Ts are separated at CEx and
WDM mux/demux to different OLTs.
PON system coexistence allows the reuse of existing fiber resources for fast deployment without a new investment; a
system upgrade to high-bandwidth services can be done by simply replacing or
adding OLT line cards.
POLAN deployment and migration
The step-by-step process of deploying a
POLAN is: 1) the first splitter is installed
in the splitter cabinet next to the OLT
rack; 2) the second splitter is installed
on each floor for a dedicated distribu-
tion group; 3) ON Ts in the work zone can
be standalone devices like WiFi routers,
or conversion devices equipped with RJ45
outlets to provide data services and PoE.
Upgrading a typical POLAN from
GPON to XGS-PON takes place in
Phase 1: Deploy the ODN, install the
GPON OLT line cards and gradually add
GPON ON T devices at endpoints.
Phase 2: The GPON OLT line cards
reach full capacity; additional services
need to be added with new XGS-PON
equipment and end devices.
Phase 3: Install the XGS-PON OLT line
cards and add the CEx to the same ODN;
install the new XGS-PON ONT devices
with the legacy GPON OLT line cards and
some GPON ONT devices still in operation.
Phase 4: Add/replace with new XGS-PON ON T devices gradually until the system is fully upgraded. Some legacy ON T
devices will still be in operation for designated applications.
Deployment challenges of
When comparing POLAN to tradi-
tional LAN technologies, it is not neces-
sarily a “better” replacement solution for
all the new access network deployment;
Upgrading from GPON to XSG-PON typically is carried out as a four-phase process. Once the network is completely
upgraded, some legacy ONT devices likely remain in operation for designated applications.