Test vendors 'tweak' devices for European FTTx market

by Meghan Fuller Hanna

But, as Stéphane Chabot, director of optical product line management at EXFO (www.exfo.com), notes, "The customer is always driving demand." And customers in Europe began to demand more advanced video services like video-on-demand and high-definition TV—services that typically generate a higher average revenue per user (ARPU), often double the ARPU of traditional services.

As a result, says Chabot, "We discussed [fibre to the home] with carriers in Italy, France, Spain, Sweden, and Germany, and they all acknowledged and agreed that for carriers to differentiate themselves, FTTH is the way to go."

While the increase in FTTH deployments in Europe has created numerous challenges for test equipment vendors, these challenges are reminiscent of those faced when Asian and North American carriers made their first forays into FTTH. The test vendors confirm they sell the same basic FTTX equipment into all markets around the world, although the devices themselves may be somewhat tailored to each market.

For example, thanks to the continent's extensive legacy copper infrastructure, European technicians are highly skilled in DSL testing. But many are new to fibre—and the region certainly does not have enough fibre technicians to support "the volume necessary to deploy these technologies very quickly," argues Chabot. "The numbers [European carriers] have published are quite aggressive; they are talking about 10 million users in three years. We've really seen the impact on European carriers' testing needs quite quickly."

The single-ended test device of choice is the tried-and-true optical time domain reflectometre (OTDR), says Chabot. Today's FTTx OTDRs are portable and lightweight and provide technician-friendly, one-button pass/fail tests. They may feature graphical user interfaces (GUIs) in a language native to whatever region they have been sold into, but, for the most part, the basic OTDR features and functionalities are the same around the world.

From an OTDR perspective, then, the challenge in Europe is the same as it is elsewhere: To see beyond the splitter, OTDRs must feature short dead zones combined with a short pulse width and a large dynamic range. At this point, every vendor has its own method for achieving these seemingly paradoxical parametres. But while all FTTx OTDRs today feature short dead zones, that need may be more critical in Europe.

In the U.S., carriers have committed to providing a backup battery for the optical network unit (ONT), which is why it is most often located outside the house. "In Europe, we don't have this specification," reports Jérôme Laferrière, fibre-optic product manager at JDSU (www.jdsu.com). "The ONT is located inside the house very close to the TV set or the PC. Therefore, as far as testing is concerned, the tools will be equivalent—we would be using the OTDR—but [the technicians] will be looking at very short links inside the house. So it can be more critical to have shorter dead zones on the European OTDR compared to the American OTDR.

"Moreover," says Laferrière, "that's another difference between the U.S. and Europe. In the U.S., the recommended test procedure is done either by an OTDR or by a loss test set. And in Europe, most of the test, if not all of the testing except in some very specific countries, is done with an OTDR only."

The optical loss test set or OLTS has a major drawback, explains Laferrière: It requires two technicians to run the test, whereas the OTDR is a single-ended test. While the OTDR itself may be more expensive than the OLTS, it results in cost savings down the road because only one technician is required to use it.

Chabot confirms that EXFO's OTDR, while similar on the hardware side to those sold elsewhere around the world, is "tweaked" to accommodate architectural differences in European FTTH networks. In typical North American networks, for example, you will find connectors both before and after the splitter, before and after the drop terminal, and at the ONT, he says. European networks, by contrast, are "spliced almost all the way. The impact is that troubleshooting points aren't necessarily the same because you don't have access to connect those fibres at every point in the network as you do in the Americas," he says.

Chabot confirms that the troubleshooting capabilities have been optimised to mitigate the limited access to European FTTH networks, which is, "most of the time, either at the ONT or at the splitter site." He says EXFO's OTDRs enable technicians to find faults more easily, even if they do not have access to the fibre between the splitter and the ONT.

Laferrière cites another architectural difference that alters the way in which OTDRs are used. Thanks to the prevalence of multi-dwelling units in Europe's larger cities, network operators must run fibre both horizontally to the building as well as vertically to the individual dwelling units.

"And you may have two different types of contractors," he says. "You have the contractors that will be installing the horizontal part of the fibre, and then later on, you have maybe a different contractor that will be installing the vertical part of it. As far as testing is concerned, that's a bit more complex because instead of making the test only once on the distribution path, like you do in the U.S., in Europe, you will probably need to do it twice because the contractors would be quite different."

As it is around the world, video is driving bandwidth growth in Europe, which has led to more carriers embracing FTTH technology. In the past, says Stefan Loeffler, product marketing manager at Agilent Technologies (www.agilent.com), there was simply no money in IPTV, whereas today, "there is high-definition content that you can buy and sell. You still can receive satellite television, but it's all standard definition, and the satellites are getting weaker and weaker because of their age. So IPTV as a competing business is gaining traction, and this has driven FTTH projects, at least as far as I can see, in France and in the Czech Republic."

Many North American carriers, by contrast, still rely on an RF video overlay in the 1550-nm wavelength to deliver at least some of their more basic video services. But in Europe, "most service providers are going from ADSL2, ADSL2+, and VDSL [to] FTTH, and most of the time, they won't choose video overlay," adds Laferrière. He attributes this difference, in part, to the unique television viewing habits of North Americans versus Europeans.

"In Europe, we watch much less TV than you do in the U.S. per home," he explains. "It is very rare in Europe to find two people within the same house watching two different TV sets, for example. That's the reason why IPTV, so far, has been very well accepted even when using ADSL or VDSL applications."

As a result, says Chabot, "the 1550-[nm window] downstream is not a big requirement" for European carriers deploying PON technology. They use the 1310-nm wavelength upstream and the 1490-nm wavelength downstream and, therefore, only require a two-wavelength power metre for testing their PON networks versus the three-wavelength power metre that is the norm in North America. Both EXFO and JDSU say they sell a two-wavelength power metre into the EMEA market.

Looking ahead, the European market may have an opportunity to differentiate itself further; although it lagged behind North American and Asia in terms of initial FTTH deployments, many European operators are already starting to look at what comes after today's GPON and EPON, most noticeably next-generation PON or NG PON. And the European Union has funded two separate WDM-PON research initiatives. "Being late on the technology may help them moving forward," says Laferrière, "going directly to the next-generation PON compared to the classical GPON that some operators are starting to implement."

And, of course, the next generation of FTTH technology will bring with it new test challenges.

Meghan Fuller Hanna is senior editor at Lightwave.