July 18, 2012
Next-Generation PON will Support at Least 40 Gbps Downstream
By Joan Engebretson
What the next generation of fiber-to-the-premises networks will look like is becoming clear, now that members of the Full Service Access Network (FSAN) have reached an agreement on what they’re calling NG-PON2.
The agreement is not actually a standard, but instead outlines the direction that standards efforts will take, explained FSAN Chair Martin Carroll, who is also a distinguished member of the technical staff at Verizon (News - Alert).
As FSAN considered the next generation of FTTP, various members proposed a wide range of approaches, including some that were “more elaborate and on the bleeding edge” and some that were “more current and readily available,” Carroll said.
Members ultimately settled on what they’re calling time and wavelength division multiplexing (TWDM) because the group believes that approach will meet target bandwidth and other requirements and can be developed relatively quickly. Standards could be ratified by as early as 2013 and products could be deployable by 2015, FSAN says.
Like today’s FTTP networks based on GPON, TWDM will rely on time division multiplexing but in addition will “use multiple wavelengths to stack TDM streams,” said Carroll.
The minimum bandwidth goal for an individual NG-PON2 is 40 Gbps downstream and 10 Gbps upstream, with total bandwidth shared among multiple subscribers. Noting that the current highest-speed PON, XG-PON, operates at 10 Gbps downstream, Carroll said the minimum target bandwidth levels should be easily reachable by using four wavelengths.
He added that systems with downstream bandwidth as great as 160 Gbps could be part of the standard, but he believes the 40 Gbps system will be considerably more cost effective.
The 40 Gbps requirement was driven by the per-customer bandwidth goal of 1 Gbps and apparently envisions each PON continuing to serve about 32 customers as with typical PONs deployed today. But bandwidth will not have to be allocated equally between all of the customers served from a single PON. Carroll believes network operators are likely to give residential customers service at rates below 1 Gbps, while business customer data rates will start around 1 Gbps.
Operators envision a wide range of use cases for NG-PON2, including support for mobile backhaul and potentially as a replacement for Sonet and SDH-based data services. Because NG-PON2 will use a point-to-multipoint approach, Carroll expects it to be more cost effective than point-to-point alternatives.
I asked Carroll whether the people creating the NG-PON2 standard would consider home run wiring – an approach that is gaining in popularity because some operators believe it is more future-proof than PON. Carroll said the emphasis is on PON, but he noted that the group also wants to have some wavelengths available for using WDM technology in more of a point-to-point configuration.
“It would be a PON architecture on the fiber side, but when you look at what the signal itself does, it would be more of a point-to-point allocation of the wavelength,” he said.
FSAN initially was primarily a North American organization dominated by the former RBOCs, but over the last decade it has become a much more global organization – and that reality has driven some of the requirements for NG-PON2. Carroll noted, for example, that NG-PON2 must co-exist not only with GPON, which has been widely deployed by Verizon, but also with XG-PON. The latter requirement was driven largely by China Telecom and China Unicom (News - Alert), Carroll said.
FSAN expects to work through the International Telecommunications Union in creating the NG-PON2 standard – another example of the global nature of the technology.
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Edited by Braden Becker
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