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PON through a service provider’s eyes

Dec 10, 20026 mins

PON offers a lot of promise, but will it deliver what service providers need?

Service providers of all sizes and shapes are wondering if passive optical networks (PON) have finally come of age, and if they are ready for deployment in their networks. Regional Bell operating companies are actively investigating PON for “greenfield” and overlay networks, as are independents and overbuilders. Even municipalities are launching PON initiatives as an “economic infrastructure” designed to improve broadband deployment in their regions. And overseas, the push for PON is even stronger, particularly in Asian markets.

But PON is still a new technology, and despite some valiant marketing efforts, the industry as a whole is still awash in acronym soup – is Ethernet PON (EPON) the best solution? Or is Gigabit PON (GPON)? And what about ATM PON (APON) and Broadband Access PON (BPON)?

This PON shootout reminds us of the early days of DSL, when vendors lined up behind CAP or DMT, and fought it out to the very end. There’s also a whiff of the old ATM vs. Ethernet battles we fought back in the ’90s. Vendors are falling into various camps and making technical arguments about the superiority of their preferred protocols.

What’s really important, however, is how well these different PON camps’ products fit the service provider vision for PON services. We’ve spent some time talking with RBOCs about what they want out of a PON solution. Here are a few of the key things they have to say:

First of all, service providers buy off on the concept of PON. Particularly for their residential and small business customers, the fact that PON shares some of the most expensive parts of the outside plant – the fiber itself and the opex-intensive splices – makes it much more attractive than point-to-point fiber solutions.

Optics are a huge chunk of the overall cost structure – particularly at the level of individual subscriber ONUs. The big telcos want all PON vendors – regardless of which Layer 2 method they choose – to converge on a single Layer 1 optics solution. The only way prices are going to come down to a reasonable (to the telco) level is for a common optical standard to bring volumes up.

Speaking of prices, ONU prices for residential customers need to be in the sub-$500 range, and those for business customers not much more than double that amount. There are, however, huge variations in the capabilities of different equipment, so some gear can potentially cost more but do more, as well.

Support for legacy services such as TDM is essential. Telcos would love to have all their data customers migrate to Ethernet-based services (notice we said services, not transport), but realistically, that’s not going to happen overnight. And even if the majority of customers demand Ethernet service, telcos are bound by their tariffs to offer T-1 and other circuit-based services. A PON solution must robustly and efficiently support these services if it is ever to be deployed in an RBOC network.

Standards – completed standards – are important to telcos, particularly the RBOCs. The RBOC folks we talk to are still, officially at least, straddling the fence between EPON and GPON until the standards are fully gelled and they can examine how these systems fit their service requirements.

The IEEE and ITU-T have been active with PON standards efforts – the IEEE in conjunction with the Ethernet in the First Mile Alliance, the ITU-T with the telco’s own Full Service Access Network (FSAN) effort. None of the RBOCs are ready to commit one way or the other – they’d be happy to see either effort develop standards that fit their networks and deliver what their customers need. To quote Ralph Ballart, vice-president of broadband and infrastructure at TRI, SBC’s research arm: “By and large, FSAN and the ITU standards have been very reflective of carrier requirements.” At the same time, however, he says, “If the IEEE comes out with a solution that is cost effective, that’s a good thing, too.” SBC has been trialing a BPON deployment in Mission Bay, Calif., where it has learned a lot about these requirements.

Ballart expects that it’s going to take a couple of years to hit the volumes required to get to the low price points, but that is compatible with the rate at which the market and technology is developing. Until then, there’s a lot of work to be done to get ready for the ramp up, and greenfield deployments are providing that learning environment. “We installed more than 100,000 new builds each year in the residential arena, and that’s perfect for PON technology,” he says. The Mission Bay trial has provided SBC with some interesting lessons learned regarding PON, including:

• In residential deployments, it makes sense to use two downstream wavelengths – one for data services and a second for broadcast TV services.

• Power budgeting is a key constraint for video services, but advances in compression (like MPEG 4) are helping with this issue.

This trial has also provided SBC with some good real-world experience regarding the outside plant deployment of PON – plant engineering, splice point location and more.

Vendors in municipalities we’re dealing with agree on PON’s potential – and pretty wholeheartedly. “Municipalities are seeing broadband deployments for their economic development advantages, and we’re seeing a ton of interest in EPON in those applications because of the ability to provide high bandwidth on behalf of multiple service providers on a wholesale basis to both homes and businesses,” says Burnie Atterbury, senior director of product marketing at Alloptic.

“ [Deployments by municipalities] are going to provide a lot of the early experience in PON and give service providers a comfort level with mass deployments,” says Gary Lee, CEO of FlexLight Networks and chairman of the PON Forum. “But the carriers are not far behind. We’re deploying GPON into tests and trials in Asia now, and the economics of the next generation of PON are clearly much more compelling than those of earlier solutions.”

The bottom line for service providers isn’t raw bandwidth, or lowest cost – it’s a system with the right mix of these attributes that can also meet their service needs. Telcos are looking for a PON solution that won’t cost them an arm and a leg, but still offers sufficient capabilities to offer all the high-bandwidth services they envision. In future columns we’ll examine some of the factors that contribute to this decision-making process – including bandwidth efficiency, legacy services support and network integration.

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