October 5, 2009

10G PON Moves Ahead

No surprise that ITU-T standards-based PON technology prevailed at last week’s Fiber to the Home (FTTH) Conference in Houston.

After all, Verizon dominates this industry. Three out of five homes—or 3.1 to 5.3 million—in North America that take FTTH subscribe to FiOS Internet. In Houston, Verizon EVP and CTO Dick Lynch was the keynoter. (For more, click here).

As for technology, Verizon first deployed FiOS over ITU-T based (G.983) BPON. In late 2007, it began using GPON (G.984), capable of 1.5 Gbps upstream, and 1.2 Gpbs downstream.

What was surprising was how often 10Gbps—which is on both ITU-T and IEEE roadmaps—surfaced as a topic for discussion.

IEEE vs. ITU-T

In terms of the standard, the IEEE is ahead of the ITU-T, having approved a 10G-Etherent (E) PON amendment to its 1 Gbps EPON standard three weeks ago.

Apart from standards work, existing IEEE PON technology is also leading in terms of deployments. According to the IEEE, 1G EPON-based products currently serve more than 30 million users worldwide.

At a certain level, the two groups are collaborating, with one ITU-T study group having adopted IEEE 10G EPON as a foundation for its NG-PON (or X-PON) recommendations. The NG PON (G.987) standard, both 10/2.5Gpbs asymmetric and 10/10Gbps symmetric phases, is expected to be in “consent” phase until June 2010.

While this roadmap is raising issues of future “coexistence,” it is possible to over-state the degree of convergence today. “We’re firmly in the ITU GPON camp,” Lynch said in a Q&A session with reporters in Houston.

If EPON continues to dominate the global market, however, at some point the cost structures at the component level will shift accordingly. The hard edge between the ITU-T and IEEE followers could soften as a result.

“We’d like to get silicon synergy,” Verizon SVP, Technology Mark Wegleitner said in a follow up, meaning “a common chip set for both.”

Video and fiber bends

Is this talk of 10G premature? “For a standard to move ahead,” said Motorola Senior Product Manager Craig Pasek in presentation at the FTTH Conference, “people really have to answer the question, ‘What’s the driver?’”

“The simple answer is video,” Pasek continued.

Anticipating a world as early as 2015 in which HD has supplanted standard definition television, with ultra (u)HD (consuming 40 Mbps per channel) coming on fast, Pasek had a clear bottom line. Higher split ratios will help, but only 10G PON can deliver at least 100 uHD channels to a single-family residence and an acceptable numbers of HD and uHD programming to subscribers within a multiple dwelling unit (MDU).

For business services, in which video conferencing becomes a larger component, Pasek said the case for 10G PON, targeting 400/400 Mbps per business, is likewise strong.

Meanwhile, there are practical coexistence questions to consider. John George, director technical marketing at OFS, who delivered a paper titled, “Optimizing PONs for 10 Gigabit—and Beyond,” addressed the implications of adopting more and higher optical wavelengths in the new standards (including RFoG).

Filtering technologies could address the increased number of wavelengths, but George said the susceptibility of loss in the higher wavelengths—“(those) from 1550nm to 1610 nm will double the bending loss”— calls for a new class of fiber.

George said that these new “ultra-bend insensitive” or “resonance assisted” fibers seem to be especially called for in the MDU access market where “there’s a desire to do stapling, and bending around corners.”

Data shared by George indicated that OFS has figured out how to minimize this loss. “We’ve got a solution today, for building GPON and emerging 10 GPONs,” he said.

—Jonathan Tombes