As carriers prepare for 40G/100G, so do test vendors

SEPTEMBER 27, 2010 By Stephen Hardy -- Only a few carriers have deployed 40-Gbps links in their networks; less than a handful have deployed 100-Gbps technology. But that doesn’t mean there isn’t interest in data rates above 10 Gbps. In a recent interview with Lightwave, Paul Brooks, a product manager in JDSU’s Communications Test and Measurement business segment, described how the increasing attractiveness of high-speed transmission technology has driven new developments in test equipment.

For many carriers evaluating high-speed technology, the first area of concern is which rate to focus on first, 40 or 100 Gbps. “For a lot of people, 100G is where they want to be -- and they want to be there pretty quickly,” Brooks reports.

For long-haul applications, that likely means fielding systems using the emerging combination of dual-polarization quadrature phase-shift keying (DP-QPSK) and coherent detection, the format the Optical Internetworking Forum (OIF) has made the focus of its long-haul DWDM ecosystem efforts. This modulation scheme has begun to filter down to 40 Gbps as well, with companies such as CoreOptics (recently purchased by Cisco) announcing 40G products and others, such as Mintera (now part of Oclaro) and JDSU promising to deliver their versions soon.

The allure of DP-QPSK and coherent detection is the ability to overcome the effects of both chromatic and polarization mode dispersion. However, Brooks asserts the fielding of systems using this technology will not decrease significantly the demand for dispersion testing at 40 and 100 Gbps via instruments such as the company’s T-BERD/MTS-6000 and MTS-8000. Carriers will want to confirm the ability of the logic and algorithms within the transmission system to detect and counter the dispersion on a particular route, he believes.

“What you’re seeing with these modules is a second-order, DSP-based measurement of what it thinks it is, but it could be fooled by other things,” Brooks explains. “These algorithms are still novel. So having proper, accurate, stable test tools gives you a much better baseline. So they’ll still play a part.”

Carriers also will remain interested in other basic measurements. “Jitter and the whole timing still play a big part as well,” adds Brooks. “We see no drop off in demand for 40-Gig jitter test sets. In fact, we’re having a lot of inquiries about next-generation -- how do you do it, what does it mean for jitter in complex modulation schemes.”

In the lab, carriers likely will have interest in the new generation of optical modulation analyzers. However, the usefulness of such capabilities in the field currently is a question in Brooks’ mind. “The biggest issue with them is that it’s not tied to any standards. So people think it’s quite useful in the lab to see how you’re tweaking your Mach-Zehnder modulators for a nice, clean I/Q diagram. But in terms of the field, it doesn’t really help you to say what it looks like when there’s no standard testing,” he says.

Regardless of whether a carrier is thinking of going straight to 100 Gbps or stopping at 40 Gbps along the way, the value of Optical Transport Network (OTN) management has become a common theme, Brooks reports.

“People who traditionally wouldn’t have looked at OTN now see it as perhaps a very attractive technology from the management perspective,” Brooks says. “ODUflex and ODU0s allow people to have a very flexible network where you can have a very efficient carrying of revenue-generating traffic and manage that traffic very effectively. And that’s really caught the imagination of carriers.”

And what catches carriers’ imaginations naturally interests test equipment vendors. “To put it mildly, this year we’ve probably put 50% or 60% of our R&D efforts into our OTN portfolio this year,” Brooks reports.

The results can be seen in JDSU’s lab and field test portfolios. For example, the company has added OTN capabilities to complement the SONET/SDH features supported within its portable ONT 503 for 40G/43G field and lab use. Meanwhile, the company’s ONT 100G module tests OTU3/OTU4 as well as 40 and 100 Gigabit Ethernet; it can be housed within the ONT 503G for use in the lab and field, as well as in the ONT 506 laboratory platform. In addition to OTN applications, the ONT 100G supports Layer 1 through 3 testing for 40 and 100 Gigabit Ethernet as well as enables evaluation of CFP and future 40G/100G transceivers.

Brooks sees the interest in OTN management as more than just a fad. “With the higher rates, the whole OTN management makes a lot more sense. So we’re seeing a lot stronger backbone value proposition for OTN there -- all the way down from ODU0s to carry GigE clients through to OTU3s,” he concludes.