40G moves back onto the agenda

June 30, 2004 Berlin, Germany -- As StrataLight ramps up the supply line for its 40-Gbit/sec optical system, FibreSystems Europe's Tami Freeman checks out whether the operators are once again ready to evaluate 40-Gbit/sec technology.

German optoelectronic component maker u2t Photonics has bagged a deal to supply its 43-Gbit/sec photodetectors to StrataLight Communications, a Campbell, CA-based OEM provider of high-capacity, long-haul transport subsystems. The components are slated for use in StrataLight's OTS-4000 subsystem, a rack-mounted shelf containing 40-Gbit/sec line cards that can replace existing 10-Gbit/sec line cards in order to upgrade the capacity of any 10- Gbit/sec DWDM transport system.

StrataLight has selected u²t's 50-GHz photodetector and photoreceiver products for its transport subsystems. According to Terry Smith, CEO of StrataLight, the firm picked u²t's products because they combine high bandwidth with very low distortion.

"The main advantage of our devices is the vast amount of bandwidth that they offer and their very clean frequency response," says Andreas Umbach, u²t's CEO. "For long-haul communications you require a very clean photodetector response. Another advantage is the power performance--you need high optical powers to overcome noise limitations in the system." u²t's products provide 3 dB bandwidth of typically more than 50 GHz and exhibit a linear response up to an optical input power of 13 dBm.

The first application of the OTS-4000 will be to upgrade the capacity of existing 10-Gbit/sec long-haul DWDM networks. The platform can upgrade on a channel-by-channel basis, offering carriers a smooth migration path from 10 to 40 Gbits/sec. "Because the OTS-4000 retrofits into existing systems, you can simply upgrade the network speed and capacity as a maintenance-type activity," explains Smith. "Our 40-Gbit/sec product competes directly with adding 10-Gbit/sec wavelengths to an existing lit fiber."

StrataLight also announced that it has chosen US manufacturer iolon (San Jose, CA) to supply widely tunable lasers for use in the OTS-4000, in a supply agreement extending through mid-2005. The manufacturer's lasers have a tuning range of more than 40 nm, enabling the 40-Gbit/sec signals to be carried on any of 80 optical wavelengths.

So does this renewed activity herald a return of interest in 40-Gbit/sec transmission? Michael Kneier, u²t's vice-president of sales and marketing, says that while there is not a large level of deployment at the moment, many systems vendors have 40-Gbit/sec trials running. He also reckons that the carriers have serious intentions to deploy 40-Gbit/sec technology sometime around the second quarter of 2005.

The StrataLight contract represents a significant win for 40-Gbit/sec specialist u²t: "I can't comment on exact figures," says Kneier, "but we have closed a deal that will last until at least the middle of 2005, with the option to extend further. This considerably contributed to the increase of our bookings by 100% from Q1 2003 to Q1 this year."

Market resurrection?

While 40 Gbits/sec was a hot topic a few years back, the downturn saw many systems vendors cancel their 40-Gbit/sec development programs or put them on hold indefinitely. But since the fourth quarter of last year, u²t's customers have renewed their interest in product development programs. "StrataLight, for example, is addressing real commercial applications," says Umbach. "This is an important deal for us and also a good sign for the 40-Gbit/sec market in general."

He continues: "There will always be places in that network where it makes a lot of sense to deploy 40-Gbit/sec applications. It won't be that the whole long-haul market will come back in a big way, but there will be upgrades needed in congested parts of the network. And in many cases the most economical solution is to use 40 Gbits/sec to upgrade these connections."

Another factor driving 40-Gbit/sec upgrades is the emergence of a new breed of IP core routers that work more effectively when they are interconnected at higher speeds. The core routers are designed to be located at the edge of different cities, routing traffic between them. "This is an application where 40-Gbit/sec long-haul transport will be more visible next year," says Umbach.

Smith echoes that view: "The new core routers are becoming an important 40-Gbit/sec market driver, especially among carriers who are field testing our subsystems. Such carriers get an important benefit from these new, extremely scalable routers, accelerating the deployment of our product." StrataLight has completed successful interoperability tests with most 10-Gbit/sec DWDM systems vendors, although it has not made public announcements of its OEM relationships.

The re-emergence of 40 Gbits/sec could also be helped by the fact that many of the previous technical concerns have been sorted out. StrataLight has tackled the issue of dispersion, for example, by using a modulation method that narrows the spectral width of the 40-Gbit/sec signal. This enables the signal to pass through 10-Gbit/sec optical filters and also improves the dispersion tolerance by a factor of three to four times compared with conventional 40-Gbit/sec signals.

"Every carrier is now well aware of the capabilities of 40 Gbits/sec and knows that their systems can handle this data rate," explains Umbach. "The systems suppliers can just replace a 10-Gbit/sec terminal with a 40-Gbit/sec terminal and achieve the same performance but with more capacity."

So this just leaves the biggest issue of the lot--cost and value for money. "We have a simple product architecture that helps keep our costs down," says Smith. "There are a small number of high-speed optical components, including the u2t photodetectors. The overall cost is then driven by volume, which is in turn driven by new applications, such as core-router interconnection."

StrataLight is currently working with its systems integrator customers to bring the cost of 40- Gbit/sec line cards down to approximately two-and-a-half times that of a corresponding 10-Gbit/sec version. The OTS-4000 is currently undergoing trials in North America and Europe, with full traffic-carrying field deployment slated for 2005.

Tami Freeman is deputy editor, FibreSystems Europe in association with LIGHTWAVE Europe.

• This article originally appeared in FibreSystems Europe in association with LIGHTWAVE Europe, May 2004, p.23.