by Stephen Hardy
The IEEE doesn't expect to ratify the standard for 10-Gbit/sec Ethernet PON (10GEPON) until late in the fall of 2009. However, as has become customary in the optical communications arena, the technology required to build and test 10GEPONs should reach carrier labs in advance of that milestone. The technology trail starts at the IC level, and EPON chip vendors report that they've already launched their development programs.
PMC-Sierra (www.pmc-sierra.com), which leads the market in EPON chip sales, was the first vendor to unveil 10GEPON reference designs, one for the central office optical line termination (OLT) unit and one for the user-located optical network unit (ONU). The March 31 announcement touted PMC-Sierra's PAS8001 OLT and the PAS9001 ONT chips; however, the reference designs feature a pair of FPGAs in each instance. Gilad Aloni, product marketing manager at PMC-Sierra, says the current two-chip configuration is a result of headroom requirements and current FPGA limitations, rather than a harbinger of what PMC-Sierra plans to provide as finished product.
The reference designs support single-channel asymmetric -- 10 Gbits/sec downstream, 1 Gbit/sec upstream -- transmission, which most observers believe will garner most of the initial deployments. (The standard also will cover symmetric 10-Gbit/sec transmission.) Aloni says that the time is right for systems houses to begin working with reference designs because he expects 10GEPON trials to begin this year, well in advance of mass deployment, which he doesn't expect to happen until 2010. While Aloni wouldn't say when PMC-Sierra plans to release finished products, he said that he expects the company will be first to market at 10 Gbits/sec and in time to support expected deployment milestones.
Loyal opposition
While representatives from PMCSierra's competition expressed general agreement with Aloni's timetable for initial trials and mass deployment, they don't feel the need to rush finished chips to market before next year. The IEEE 802.3av 10GEPON draft will remain open to technical changes until this November, notes Zino Chair, vice president of marketing at chipmaker Cortina Systems (www.cortina-systems.com). "On the reference designs, people are not expecting silicon on those things," he says. "Even if you see [silicon before next year], there will have to be a re-spin for sure."
Of the sources contacted for this article, Chair has the most relaxed view of when he needs to have reference designs and chips in place. "You might have some people just playing with it in the lab on the research side of things, but we have not really seen our customers pushing to start working seriously with reference designs," he says."I think more likely late this year, early next year, that's where we'll see the demand." To get a jump on the task at hand, Chair says Cortina's engineers currently have focused on the analog aspects of 10GEPON transmission requirements, with the idea of moving to the digital elements once the standards process closes to technical changes.
Conversely, Greg Caltabiano, president and CEO of Teknovus (www.teknovus.com), reports that his company is "getting a lot of pressure" from its customers for 10GEPON reference designs. As a result, Teknovus -- which is second in EPON chip market share -- is "deeply engaged" with its customers on the development of FPGAs with 10GEPON features, with an eye toward having silicon available at the beginning of next year.
Centillium Communications (www.centillium.com) CTO Sriraman Chari, whose company supplies chips used in NTT's EPON deployment, also feels comfortable putting his engineers to work on 10-Gbit/sec chips. In fact, they're working on developing the FPGA and ASSP versions simultaneously, he says, to ensure that the company has standard ICs available when customers are expected to require them. He says he foresees early proof-of-concept trials this year (likely not based on standard silicon), which will evolve toward more ambitious tests in 2009. Chari expects the first deployments to occur in Japan.
Bits and pieces
With only one company publicly offering access to its 10GEPON technology so far, the full roster of features designers can expect from chip suppliers remains unclear. However, our sources offered some hints.
The most direct indications, of course, came from PMC-Sierra. Along the lines of the expected 802.3av standards, the announced reference designs offer backwards compatibility with currently deployed GEPON technology and related autodetection and dynamic bandwidth allocation as well as support for up to 128 ONUs per OLT.
The reference designs also offer "standard encryption," according to the company. Full security features were not part of the original GEPON standards; Ethernet security specifications are part of other IEEE 802 standards. The lack of full security feature specifications in the GEPON standard led several countries (particularly in Asia) to develop their own security features that they imposed on their equipment suppliers; most of these involved the handling of encryption keys, according to Chari. Chip vendors therefore had to develop devices specific to individual markets.
Teknovus reports that security features based on IEEE P802.1AE, ratified in 2006, "is what 10GEPON vendors are targeting now and what carriers are asking for." Other sources aren't as optimistic about such a consensus. Several of them predict that countries will ensure backwards compatibility with fielded systems by sticking to the requirements they imposed for GEPON. However, they also expect that these countries will follow China's lead and publicly publish the specifications, which will make compliance easier to achieve.
Another salient feature of the PMC-Sierra reference design is its support for the single-channel XFI optical transceiver interface. Aloni and the other chipmaker representatives say that system vendors want their OLT blades to offer a high degree of density, which points toward the use of transceivers no bigger than the XFP. Support of the XFI interface should be a common feature of 10GEPON devices, OLT chips in particular.
Since they don't have announced products, PMC-Sierra's competition offered limited details about their upcoming devices. Chari noted that Centillium currently has Japanese requirements in focus, including the integration of PHY, router, and voice-over-IP functions in its ONU device. The company also expects the functions provided by their devices will dovetail with Japan's "next-generation network" initiatives, with support for the quality of service and service and provider segmentation requirements Japanese applications will demand. That said, Chari expects that Centillium will not be so focused on Japan that it misses the mark in other markets. Programmable aspects of the devices should aid in this effort.
Caltabiano did not tip Teknovus's hand very much, although he did underscore the spirit of flexibility incorporated into the GEPON standard should remain at 10 Gbits/sec -- and that 10GEPON chips should not get in the way of providing systems houses and carriers with options.
Finally, Chair says that Cortina will leverage its existing experience with the development of 10-Gigabit Ethernet semiconductors in the design of its 10GEPON devices. "In our case, for sure, we're very comfortable with multiple interfaces on the same silicon," he says by way of example. "The key is cost, so if you don't have density, I think you're going to have an issue with really hitting the costs. So our plan is that we're really going to be pushing for density."
Stephen Hardy is the editorial director and associate publisher of Lightwave.
The trouble with 10GEPON
While the sources quoted in this story all have active 10GEPON chip development programs underway, not every device supplier with EPON experience is galloping down that path.
"It's a market that we're monitoring closely. Right now our focus has been on GPON," says Pranay Aiya, director of marketing, central office, Conexant Systems Inc. (www.conexant.com). Conexant last year announced its Xenon III devices for PON residential gateways. The company debuted a IIIG version for GPON and IIIE version for EPON. Based on the company's ensuing experiences, it likes what it sees in the GPON space better than the emerging 10GEPON market.
"It seems, to us at least, that it's going to be a Japan-only market," says Aiya of the 10GEPON opportunity. "The rest of the world is probably going to transition to GPON for now. Just purely given that there are fundamental cost issues involved around the [10GEPON] technology, where the technology is, especially with the optics and then the coexistence of this technology and the prior generation of PON."
The other Asian markets, notably China and Korea, where GEPON has been deployed aren't ready for 10GEPON, Aiya believes. "I haven't seen even Korea or China -- they're working the 1G and even maybe looking at the 2.5G GPON as the solution," he explains.
Meanwhile, the costs associated with the optical requirements of increasing bit rates by a factor of 10 are enough to give the company -- and the market, Conexant believes -- pause when it comes to 10GEPON as well. Rajiv Dighe, Conexant's PON product line manager, points out that the move from BPON to 2.5-Gbit/sec GPON necessitated the use of avalanche photodiodes instead of less expensive PIN-based receiver technology for optical transceivers. The 10X leap from GEPON to 10GEPON likely will lead to a significant cost increase in the first technology generation, he believes, leading to questions about how ready the market will be to deploy the technology.
But Aiya makes clear that Conexant doesn't intend to dismiss 10GEPON out of hand. "There's definitely a market, in the sense that this has always been a bandwidth-conscious market. So if you can come in with 10X the speed, obviously there will be people signing up for it," he concludes. "But at what price is, I think, the question."