MSO APPLICATION CHALLENGES
Fiber-to-the-Home in the MSO Community
Successes in HFC system have led to MSOs generally not as
enthusiastic as Telcos in FTTH development activities.
However, Fiber is being perceived as the ultimate transmission
medium and Fiber-to-the-Home access will some day in future be
preferred by customers when choosing service provider.
Most PON-based FTTH systems (EPON, GPON) available today
were developed to suit the Telco network environment. There are
some challenges in adopting such system in MSO’s environment.
This presentation highlights some of those challenges to promote
dialogues for their resolutions between MSOs, Vendors and
Recently, some systems are available for MSO to carry HFC signals
on PON. But over the long term, HFC has its own set of challenges
which is outside the scope of this presentation.
Main Challenges for EPON/GPON Adoption by MSO
Upstream RF Channel for STB Return
Back Office Support
Fiber Counts Required
(Note – This is not an exhaustive list)
The Upstream RF Channel Challenge
The ‘standard’ way of supporting TV broadcast in EPON/GPON
system is by mean of RF overlay using an additional wavelength.
(The next slide shows the configuration)
The current ‘standard’ only supports RF overlay in the Downstream
direction using 1550nm wavelength. RF return in the Upstream
direction, which is needed for Video-on-Demand service, is not
Currently, there are vendor specific solutions available that convert
the RF from customer’s STB to Ethernet and then transport the return
channel as Data. This requires operating the DNCS in a different
mode that may be incompatible with existing configuration.
It is highly desirable that a non-vendor specific solution be designed,
commonly adopted by all vendors, and included as ‘standard’.
EPON/GPON RF Overlay Configuration
Headend Passive Optical Netowork (PON)
Up to 20 km
(1:16~32) ONT TP
1310nm ONT TV
IP Network Home
Analog Chs Analog
BC DTV Transmitter
Current Vendor Specific RF Return Solution
OLT PON ONT Cat.5
1490nm nm RF to Eth.
The In-House Wiring Challenge
‘Standard’ EPON/GPON ONTs deliver service by separate
– TV service at Coax port
– Data service at RJ45 Ethernet port
– Telephone service at RJ11 POTS port
MSO’s existing practice is to have all services delivered on Coax
MoCA is one possible solution that would enable Data service to be
carried on the Coax wiring, but this requires MoCA gateway devices
at home and complicates installation.
A common solution (whether MoCA or something else) advocated by
the MSO community will help vendors improve on ONT functions to
better serve our needs at lower costs.
The Back Office Support Challenge
Back Office Support includes:
– Service Provisioning / Activation / Deactivation
– Traffic volume accounting
Since MSO are typically delivering services by DOCSIS platform, the
Back Office systems are tailored based on DOCSIS parameters.
EPON/GPON FTTH platforms work on different set of protocols and
will be different in control plane structure and reporting parameters.
It will not be desirable to have a separate Back Office System to
support DOCSIS service delivery and another one for FTTH service
Harmonizing the two different platform with one Back Office support
is a major undertaking and it requires substantial resources and time.
The Distance Limitation Challenge
The current distance limit in EPON/GPON standards is 20km.
20km is not adequate for MSO since CATV hubs typically serve
distances up to 50~60km.
Most vendors can support service distances much longer than 20km
if there is no requirement for the RF Overlay.
Video quality requirements on the RF Overlay channel limit the
service distance in the following ways:
– Optical launch power limited by the SBS (Stimulated Brillouin
Scattering) threshold which is around +18dBm
– Optical receiver sensitivity limited by the CNR requirement to
about -6dBm for channel loading of 80 analog plus 20 QAM
– Passive splitters required for 1:32 split already consume
16~17dB of the available optical budget.
The Trunk Protection Challenge
‘Standard’ EPON/GPON configuration does not provide diverse path
protection on the PON line
MSOs need to cover typical service distances of 50~60km; and
leaving such distance unprotected is risky
The need for trunk protection should be advocated to the Vendor
Community should be made at each possible opportunity
Even more desirable is that the PON line protection requirement be
included in the respective EPON and GPON standards so that
protection schemes across different vendors are compatible.
The Fiber-Counts Challenge
The ‘Standard’ 1:32 split EPON/GPON model imposes the needs for
very high count fiber cable in the serving area
For example: an community of 10,000 homes will need a minimum of
313 fiber-strands homing at the OLT site
While the costs for installing high count cable is not prohibitive in
Greenfield area, it is not the same case in areas where the optical
fiber infrastructure has been laid
Some vendor do offer the option of using 1:64 split in the PON line,
however this will also mean a further reduction of service distance to
much less than 20km
Fiber connection all the way from Service Provider to Customers is
the ultimate future proof access medium.
MSOs’ existing access method may still be adequate, but its never
too early to start investigating challenges ahead and planning for next
Although EPON/GPON FTTH solutions have been proven by Telcos
around the world, it will not be just a simple adoption if MSOs choose
to use the same solution.
The willingness of vendors to tailor FTTH systems towards MSO’s
application environment depends on potential demand. Continuous
dialogue between MSOs on this subject will help developing common
demands which in turn will lower the costs for those tailored changes.