10G PON Technologies: Where Do They Make Sense?
Operators that have chosen a passive optical network (PON)-based fiber access network strategy should find that residential Internet services can be more than satisfied by GPON access technology for many years to come.
GPON, which offers downstream speeds of 2.5 Gbit/s on the PON, is, according to vendors of optical access kit, easily capable of supporting the requirements of residential subscribers even during busy hours, using a typical split of 1:32.
PON-based access networks -- GPON and EPON (which offers 1 Gbit/s on the PON) -- are relatively simple to deploy compared with Active Ethernet. They can also be used for backhaul in situations where FTTH is not a market imperative, for instance where loop lengths are short and VDSL2 and future fast copper technologies are appropriate.
On the face of it, Gigabit and 2.5-Gigabit PON have a solid business and technical case in residential access. Indeed, the 10Gbit/s standard for GPON (XG-PON1) hasn't really taken off outside a couple of Asian markets -- largely because the asymmetric speeds it offers limit its use for business applications.
So why are vendors that are developing the next generation of PON systems -- specifically, NG-PON2 -- so optimistic about its prospects?
The principal reasons are: The same optical distribution network (ODN) can be used for NG-PON2 and GPON, so providing vendors with a ready market and a straightforward overlay; and it allows stepwise upgrading of the capacity of the ODN to include symmetric 10Gbit/s services on dedicated wavelengths (the NG-PON2 standard is a hybrid of time- and wavelength-division multiplexing approaches) if required. This enables operators to introduce business services over the same infrastructure as their residential services and be prepared to offer faster residential services in the future when the market demands it.
With NG-PON2, the advantages of flexibility and upgradeability that Active Ethernet has over PON-based networks are narrowed.
Furthermore, optical access vendors expect a very large market to emerge for fronthaul and backhaul applications in 4G and 5G mobile networks during the next few years. Remote radio heads and basestations will need connecting over very large numbers of low-latency, high-capacity links and its proponents say NG-PON2 is well placed to deliver this at lowest cost (though some technical challenges remain to be resolved on issues, such as synchronization).
But however well the NG-PON2 advocates paint it, the picture will not make sense unless there are advances in optical technology that can bring down the cost of the new components needed to deliver WDM. This is something that has held back the use of (non-standardized) WDM-PON approaches during the past few years, largely limiting their appeal to data center connectivity. And if these optical component issues are solved, then we may see WDM-PON and NGPON-2 challenging for the same market opportunities.
The latest Heavy Reading Insider report, "Next-Generation PON: Status and Prospects," examines technology developments and standardization efforts for the next generation of PON, and considers which technologies will be used and for what. It looks at how specific markets for next-gen PON will evolve, and compares the focus and portfolios of vendors. Finally, it profiles 13 of the leading suppliers of PON equipment.
— Danny Dicks, Analyst, Heavy Reading Insider
Next-Generation PON: Status and Prospects, a 22-page report, is available as part of an annual subscription (12 monthly issues) to Heavy Reading Insider, priced at $1,499. This report is available for $595. To subscribe, please visit: www.heavyreading.com/insider.