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ANALYSIS & OPINION CABLE TV NETWORKS
Figure 1: HFC Node+3 Network Line Extender Amp Taps Drop Node Premise Headend Node + 3
In addition, the FTTH network will require drop cables from the plant to each home. Another important consideration is fibre
Figure 2: HFC Node+0 Network New Mini-Nodes Taps
(Add 30 fibres or DWDM)
Headend Node + 0 Figure 3: PON Network Splitter PDOs (connector boxes)
64 home group
Fibre
Distribution point/Outdoor OLT location
Headend PON
In this example, each splitter feeds up to 64 homes. 1x64 PON requires one fibre per splitter, 1x32 PON requires 2 fibres per splitter location (2 splitter at each location)
At 2 fibres per splitter location, we require 24 fibres from the OLT to this group of 12
Fibre Drop Premise HFC
New Fibre cable
For this example, 14 Line Extenders
are converted into Mini-Nodes. If each Mini-Node requires 2 fibres, we require 28 additional fibres to the headend
Drop Node Premise
availability for business services. In a primarily residential network, many business services can ride the same coax or PON network used to serve homes. In some cases, however, the operator may require more. A business might demand their own dedicated fibre for security purposes, or for an unusually high bandwidth demand. Tey might require a wholly different
architecture, such as a ring, for route protection. For this reason, no matter what the required count for serving residential requirements, there should be extra fibres installed for future business services. Te amount will depend upon the commercial density of the particular geographic area. When it comes to cellular networks and
upcoming 5G, these networks traditionally use fibre, but with very small cell sizes, a Coax or PON network could accommodate the required bandwidth. Some Radio Access Networks (RAN) work with dark fibre connecting several radio heads to a common controller. Te bottom line is extra fibre strands should
be planned to accommodate any future requirements.
employing high-output nodes and reversing the tap strings in the coax, but these methods only have a slight effect in the overall node count while increasing the length of service outages involved in the conversion.
Overcoming challenges What if we create a PON network from the former node location instead? Figure 3 shows that the neighbourhoods previously served by a
line extender are now served by a splitter location instead. By remoting the OLT to this distribution point, we can overcome the fibre shortage and loss budget problems mentioned above. If we compare the diagrams for these two
network options, it is apparent that the required fibre counts are very similar, but the total sheath distance of fibre required is different because only the FTTH network requires installation of new fibre cable beyond the node/splitter location.
A future-ready network Ultimately, the architecture required to build advanced networks is remarkably similar between PON/FTTH and HFC Node+0. We can build lots of ‘transport’ plant to feed these fibre distribution clusters, or we can make prudent use of active and passive solutions, including Remote OLTs and DWDM, in order to keep the construction of new fibre cable to a minimum. By analysing the financial implications of the
various options, an operator can decide the best choice for their particular situation and be prepared for bandwidth demands that the future will bring.l
Vanesa Diaz is market development manager EMEA at Corning Optical Communications
Issue 20 • Summer 2018 FIBRE SYSTEMS 19 HFC
When faced with insufficient fibres to feed the aggregation point, the only option was to overlay more fibre cables from the headend out
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