Metro 100G: An OFC/NFOEC Reporter's Notebook

As is the case every year, OFC/NFOEC 2012 in Los Angeles last week featured a variety of technology and application themes. “Cost-effective 100G in the metro” was among the most prominent.

As is the case every year, OFC/NFOEC 2012 in Los Angeles last week featured a variety of technology and application themes. “Cost-effective 100G in the metro” was among the most prominent. Since a combination of a hectic schedule and the (allegedly temporary) inability of our new content management system to support blogging prevented me from posting my standard Reporter’s Notebook trade show items, I thought I’d compensate by filing a few post-show notebook-style stories, of which this is the first.

While 100-Gbps technology has only recently begun deployment in long-haul networks, Ihab Tarazi, vice president, global network planning at Verizon, heralded the advent of metro deployments when he told the audience at the OSA Executive Forum March 5 that he expected to roll out 100G in the metro early next year. Tarazi didn’t say exactly where this might occur, but sources at the show agree that the general opportunity is in links from about 40 km to maybe 600 km (although some suggested even longer runs). Data center interconnect will provide the greatest catalyst for such deployments, most believe, with wireless backhaul offered in explanation as well.

The difference in reach isn’t the only area in which 100G metro will differ from 100G long haul. Whereas the industry rallied around the OIF long-haul DWDM specifications – including the use of dual-polarization quadrature phase-shift keying (DP-QPSK) with coherent detection as the modulation format of choice – the metro appears more of a free-for-all. Four primary options have emerged: DP-QPSK, 16-QAM, 4x25-Gbps (or, really, 4x28G if you include overhead) using optical duobinary (ODB) modulation, and 4x25-Gbps using on/off keying (OOK). And, just to add further spice, module vendors targeting 10x10-Gbps approaches have their eyes on the shorter-reach end of the metro spectrum as well.

[UPDATED] Camps have already started to form around the different approaches. Sources at Transmode and Fujitsu Network Communications told me that they’re fine with DP-QPSK. However, Alcatel-Lucent (Euronext Paris and NYSE: ALU) and Ciena (NASDAQ: CIEN) both touted the applicability of coherent 16-QAM to the metro as well as to 400-Gbps applications. Meanwhile, ECI Telecom announced that 4x25-Gbps development is underway in collaboration with chip vendor Multiphy, while ADVA Optical Networking used the show to demonstrate its previously announced 4x25-Gbps approach. ADVA's 4x25G efforts use ODB; contrary to what we previously reported, ECI Telecom will take an OOK approach.

Participants have described the OIF long-haul effort as a way to “avoid the mistakes of 40G” – that is, so many technology options that none could gain enough market traction to enjoy significant cost reduction. So is the industry in danger of repeating those mistakes in the metro?

Interestingly, few people with whom I spoke believe this to be the case. For example, Karen Liu, an analyst at Ovum, said at a Sunday evening seminar on 40 and 100 Gbps that she believes the 4x25G approach looks enough like what the IEEE has in mind for shorter reaches that it will be seen as an extension of that effort. And Christoph Glingener, CTO at ADVA Optical Networking (FSE: ADV), says that unlike 40 Gbps, 4x25-Gbps approaches don’t require high volumes to deliver cost savings. He asserted that ADVA’s approach is already delivering 100-Gbps capabilities to customers in the field at price points below 10x10 Gbps.

As for 16-QAM, Ciena’s Joe Berthold told the Executive Forum audience that 16-QAM line cards can use optical components designed to the OIF’s DP-QPSK specifications; other sources on the show floor corroborated that assessment. This means that metro 100-Gbps line cards could benefit from the cost-reduction possibilities presented by the entire 100-Gbps coherent marketplace.

Regardless, it appears that carriers will have several options to weigh when it comes time to bring 100 Gbps to their metro networks. Tarazi said he plans to use a coherent-based approach to blend with what Verizon is doing in the long haul. But given the interest in 4x25G approaches, it’s likely that carriers will prove as diverse in their technology selections as their systems suppliers.

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