TORONTO – What’s not to like about RfoG, asked speakers at the SCTE Canadian Summit Tuesday morning at the Metro Toronto Convention Centre?
Suppliers, of course, offered a number of compelling reasons for cable operators to deploy Radio Frequency over Glass technology as a way to reduce operating costs while extending the capacity of their existing hybrid fibre-coaxial infrastructures.
As explained by Mike Emmendorfer, senior director of solution architecture and strategy for Arris, RFoG leverages traditional HFC components already in place, increases both upstream and downstream bandwidth capacity, supports DOCSIS services, enables easy migration to Ethernet Passive Optical Network (EPON) and Gigabit PON (GPON) where and when needed, and results in reduced operational expenses and increased service reliability.
“The costs to install RFoG have become competitive with traditional HFC,” Emmendorfer said. “When comparing it to traditional HFC, we think the great application for RFoG would be greenfield applications, new developments or planned plant upgrade scenarios.”
He added that RFoG infrastructure cost advantages currently do not justify rebuilding an existing HFC infrastructure that is fully functional today. “So it is not a replacement technology for existing HFC infrastructure,” Emmendorfer said.
However, he noted RFoG architectures are more cost effective to build and activate in lower-density communities than traditional HFC infrastructures. Specifically, the enablement costs for deploying RFoG will be lower than HFC deployments for scenarios with node densities of fewer than 105 homes passed per mile, he said.
In addition, the reason RFoG is able to reduce ongoing operational costs is because the technology is completely passive in the outside plant, Emmendorfer explained. “
One potential market where Canadian cable operators may find RFoG technology to be a sensible solution is in small or remote population centres currently served by satellite competitors, Emmendorfer said.
He explained RFoG technology currently supports a standard 32 fibre splits at 20 kilometres. However, using repeater technology, this could be extended to 80 kilometres. “So by adding a repeater or a node in the outside plant, the operator would have the flexibility to leverage an existing facility, but serve the extended communities of these new build opportunities,” Emmendorfer said. “It doesn’t force an operator to add facilities to meet the distance constraints of RFoG.”
Ketan Gadkari, director of RF and optical systems for Alloptic (recently acquired by CTDI), spoke during the same breakout session and shared information about some RFoG field trials conducted by his company last year in Canada. Typically, the field trials were greenfield scenarios that were extensions of existing HFC plants, with deployment densities between 200 to 500 homes, Gadkari said.
In the case of one Ontario cable operator he declined to name, the challenge was reaching a new 300-home housing development that was 45 kilometres away from the operator’s hub. “In our experience, almost every deployment that we’ve done has had a meeting point in the middle, because it has been longer than 20 kilometres in terms of distance,” Gadkari said.
He explained the two common fibre splitter approaches are either to use cascading splits or to house the splitters in a central cabinet and run fibre from the cabinet to each home.
“In this particular case, all of the splitters were housed within the cabinet. The reason for that is it adds a little more flexibility to how you want to offer your services going forward,” Gadkari said. “If you have fibre going from the cabinet to the home, then you can offer other services to that specific customer on an as-needed basis.”
During a second presentation held later in the day, Fritz Amt of Amt Consulting, a consultant for CommScope, advocated using distributed architectures for RFoG deployments, rather than a centralized-splitter approach.
He explained a distributed-tap architecture uses eight 4-port taps cascaded along one fibre, accommodating 32 homes per fibre. In comparison, a distributed-splitter architecture uses eight 4-port splitters each served by its own fibre from an eight-way splitter, thereby serving 32 homes via a combination of splitters and increased fibre use. As already explained, a centralized-splitter infrastructure requires one fibre for each home served.
One concern on the minds of attendees and speakers alike was the issue of optical beat interference (OBI) which is a potential problem for RFoG deployments.
Emmendorfer explained that because RFoG ONUs share the same optical frequency, if two or more RFoG ONUs in close proximity were to transmit at exactly the same time, there is the potential for interference.
“One of the things we’re examining, and really the whole industry through the SCTE working groups, is this OBI issue – how often it comes up, and what some of the mitigation techniques are,” Emmendorfer said.
Added Gadkari: “From an experience standpoint, we have more than 60,000 RFoG ONUs deployed in the field now, and [OBI] hasn’t been an issue.”
