RFoG Meets DOCSIS 3.1
ORLANDO — Traditional thinking in cable has been that when it comes to fiber-to-the-home (FTTH) architectures, radio frequency over glass (RFoG) is a transition technology leading to the eventual migration to Ethernet passive optical networks (EPON). New DOCSIS 3.1 features combined with next-generation RFoG enhancements are challenging this assumption, according to panelists speaking at the SCTE Cable-Tec Expo yesterday.
Bill Dawson, vice president of business development and product strategy for ARRIS Access, Transport & Supplies, noted DOCSIS 3.1 eventually will support downstream rates of 10 Gbps and upstream capacity of 2.5 Gbps.
“When we combine advances with DOCSIS 3.1 and RFoG, they will ultimately offer capacity and performance equal to or better than EPON or GPON,” Dawson said. “It’s much more cable-friendly and evolutionary. It’s forklift-free to get to higher capacity and higher service levels.” He urged cable operators to consider seriously RFoG both as their short-term and long-term roadmaps for FTTH.
Donald Gall, CTO at Pulse Broadband, noted RFoG offers several benefits compared to traditional HFC networks. These include single-mode fiber-optic cable with more bandwidth, distributed tap architecture that supports drops in excess of 1,000 feet, no CLI testing needed, and direct feeds with no active devices between the headend/hub and customers.
The architecture is especially cost-effective for greenfield deployments and in less densely populated areas like rural settings. Gall noted Pulse currently is building a RFoG network for an electric cooperative. “The network has two to 10 homes passed per mile,” he said. “We can build a RFoG plant for that at really reasonable costs.”
Gall added that the crossover point for greenfield deployments of RFoG versus 1 GHz HFC generally is between 75 and 100 homes per mile. Once an operator reached critical mass of homes passed, HFC becomes more cost-effective, mainly due to the cost of the network interface unit (NUI). “Without the NIU, this is way cheaper than anything you can do with HFC,” Gall added. “If you’re doing an upgrade without replacing the coax, then that will be cheaper. But you have to allow for the fact that the HFC is 15 years old.”
When considering the costs of switching to a RFoG architecture versus relying on your HFC plant going forward, Zoran Maricevic, senior director/Solution Architectures and Strategy at ARRIS Group Inc., said it’s essential to keep in mind high-bandwidth-consumption growth rates. Maricevic noted that, historically, compound annual growth rates of bandwidth consumption is about 50 percent a year. His financial analysis showed that a system with 1 million homes passes and with 2000 service groups of 500 homes each, will need to be segmented to accommodate demand in 4.1 years. Furthermore, additional segmentation will be required every 1.7 years after that. This segmentation requirement translates to a cost of roughly $50 for every home passed per year, or a net present value of roughly $315.83 million dollars in 10 years.
— Jennifer Whalen