40G passive optical networks take shape

July 18, 2012 // By Rick Merritt
The Full Service Access Network, an alliance of about 85 telecom providers and their vendors, picked a technical proposal for 40 Gbit/second passive optical networks. The group is hammering out details of its recommendations in hopes they can be ratified as standards next year and emerge in shipping systems in 2015

The FSAN group culled more than a dozen proposals down to one supported by several companies including Alcatel-Lucent, Huawei and ZTE that calls for use of time and wavelength division multiplexed (TWDM) technology. The proposal includes optional support for a wavelength division multiplexed overlay backed by Nokia Siemens Networks among others.

The group will submit its recommendations to the International Telecommunications Union for inclusion in the so-called NG-PON2 standard. It is the follow on to today’s XGPON technology that delivers 10 Gbits/s downstream and 2.5 Gbits/s upstream.

The proposal calls for supporting a stack of at least four wavelengths each carrying 10 Gbits/s of data. Engineers have discussed versions of the technology using as many as eight wavelengths to deliver 80 Gbits/s to end users and a quarter of that capacity upstream to the carrier network.

“The easiest thing about TWDM is it’s a known, proven technology and at least some components are already available for aspects of the system,” said Martin Carroll, chairman of FSAN and a distinguished member of technical staff at Verizon. “Operators unanimously agreed that was the technology we wanted to focus on,” he said.

Engineers must now fit which wavelengths the new technology will use into existing optical spectrum bands operators have dedicated to PONs, RF video and other applications, said Carroll. The proposal is expected to support distances of 40 kilometers without field amplifiers.

“That’s a huge challenge with the technology today,” he said.

The FSAN group is one of a handful working on bolstering next-generation optical networking speeds.

An IEEE group is meeting this week to discuss the future of Ethernet. One working group is debating multiple proposals for lowering the costs of today’s 100 Gbits/s Ethernet to accelerate deployments of the technology. Another is continuing work to assess the next big leap which has included a debate between advocates of 400 Gbits/s and those favoring a terabit/s.

Meanwhile, the Optical Internetworking Group