ROADM advances: An OFC/NFOEC 2012 Reporter's Notebook

Despite what previous editions of this notebook series might lead you to believe, not everything announced or discussed at OFC/NFOEC 2012 in Los Angeles last month directly pertained to 100 Gbps. The addition of new capabilities to reconfigurable optical add/drop multiplexers (ROADMs) – particularly colorless, directionless, contentionless, and gridless features – also proved a major focus. Gridless and contentionless abilities in particular featured prominently.

The advent of gridless capabilities –the ability to move off of the ITU wavelength grid to allocate channel spectrum as needed – has arrived quickly since I first heard discussion of it at ECOC 2010. Finisar and Oclaro were the first to discuss wavelength-selective switches (WSSs) for such applications, with Finisar wresting a leadership role. However, by last month it seemed the gridless bandwagon was starting to fill.

JDSU showed off its 1x20 TrueFlex offering, which it had begun sampling early this year. The unit offers a twin WSS configuration and should begin commercial shipments in the second half of 2012.

Nistica jumped into the game with its FOURIER line of waveblocking arrays, including a 15-port device that supports 25-GHz channel spacing and gridless performance with sub-5-GHz granularity.

CoAdna also announced a twin 1x23 WSS with gridless capabilities, based on its new Gen-2 LightFlow technology. It offers 12.5-GHz granularity.

Generally speaking, carriers have associated gridless capabilities with data rates above 100 Gbps. Moving off the grid will likely be necessary for the complex modulation formats that 400 Gbps and 1 Tbps will require, as well as to support superchannels. At ECOC 2010, such requirements appeared a long way off. However, with Ciena and Alcatel-Lucent announcing 400-Gbps capabilities in the near term, it appears carriers may have that option sooner than one might have expected. Ihab Tarazi, vice president, global network planning at Verizon, told attendees as the Optical Society of America’s Executive Forum that his organization will test gridless ROADM capabilities this year with an eye toward possible deployment in 2013. I didn’t take this to mean that he expects to field 400 Gbps next year as well – but you never know.

Meanwhile, several companies offered looks at an important building block for contentionless ROADMs, the multi-cast switch. NeoPhotonics took the wraps off of its device, which will come in a dual 8x16 configuration out of the gate. The company expects its design could support 8x12 or 8x24 configurations as well.

JDSU offered its own take on the multi-cast switch as part of its TrueFlex family, while CoAdna unveiled the Twin BXC, which offers two multicast switches in one package. We can expect Calient to offer such a switch based on its MEMS technology in the fairly near future as well.

The jury still seems to be out as far as how much demand there will be for contentionless capabilities, but it appears that carriers with a demand for contentionless ROADMs will soon have plenty of options.