FIBER-TO-THE-HOME: MSO APPLICATION CHALLENGES 2 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 Standards communities. 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. 3 Main Challenges for EPON/GPON Adoption by MSO Upstream RF Channel for STB Return In-house wiring Back Office Support Distance Limitations Trunk Protection Fiber Counts Required (Note – This is not an exhaustive list) 4 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 supported. 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’. 5 EPON/GPON RF Overlay Configuration Headend Passive Optical Netowork (PON) Up to 20 km ONU ONU Voice Passive Cat.5 PC Optical Splitter (1:16~32) ONT TP Telephone Coax Data OLT STB Switch Internet 1310nm ONT TV 1490nm Customer IP Network Home 1550 IPTV nm ONU Analog Chs Analog Combiner RF Optical Network BC DTV Transmitter 6 Current Vendor Specific RF Return Solution Headend Telephone TP Data Switch OLT PON ONT Cat.5 PC 1310nm 1550 1490nm nm RF to Eth. BC+NC+QPSK (Optical) Coax BC+NC STB (RF) DNCS TV QPSK Optical Mod. Xmtr. HFC Customer Home QPSK Optical Demod. Rcvr. 7 The In-House Wiring Challenge ‘Standard’ EPON/GPON ONTs deliver service by separate interfaces: – 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 home wiring. 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. 8 The Back Office Support Challenge Back Office Support includes: – Service Provisioning / Activation / Deactivation – Traffic volume accounting – Billing 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 delivery Harmonizing the two different platform with one Back Office support is a major undertaking and it requires substantial resources and time. 9 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. 10 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. 11 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 12 Summary 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 generation solutions. 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.
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