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Taking baby steps toward fiber

Aug 03, 20043 mins
System ManagementTelecommunications Industry

The telecom industry in general is focused on fiber, but not everyone sees the same thing through the viewfinder. Some telcos are calling fiber-to-the-premise “fiber,” others are calling fiber-to-the-curb “fiber,” and still others are calling fiber-to the-neighborhood “fiber”. Poll a roomful of telco execs, and you’ll probably hear a dozen different definitions of what they mean by “fiber.”

Given this level of confusion, vendors are taking a page from the Tony Blair playbook and proposing a “third way” – providing new generations of DSL gear that straddles the fence between copper and fiber. DSL chip vendors and technology developers (whether they’re in the chip vendor’s employ or in a university lab somewhere) have been making this middle ground more feasible by improving the capabilities of copper rather dramatically.

 Vendors are starting to ship real quantities of ADSL2+ chips, and they’re shipping them at prices not significantly higher than “plain old” ADSL. Faster variants are available and are getting faster by the day. TI, for example, has recently proposed backward-compatible 100M bit/sec symmetric Uni-DSL.

Of course this is nothing new. DSL vendors have been talking about fiber upgrade paths for years and years — “futureproofing,” “Gig-E backhaul,” “video-ready.” You’ve heard these (and more) buzzwords for quite some time.

 And indeed broadband loop carriers (BLC) from a number of vendors have been ready, to varying degrees, for a fiber-to-the-user future. But the size of these units, and the way they are engineered into the network, means that while they’ll be close to the user, they won’t be really close. In other words, they’ll be good for true fiber-to-the-user deployments, but in situations where copper provides the final bit of access to the user, distance limitations may cause bandwidth shortfalls for services such as video.

 Which leads us to the newest development – the launch of small and inexpensive hardened DSLAMs/BLCs that can be mounted on a pole, pad, cabinet or even on the side of a building. These DSLAMs are weatherproof. One vendor, Pedestal Networks, demos its system submerged inside a tank of water at trade shows – always good for attracting attention. Add to the mix line power, removing a fairly significant amount of plant engineering and capital, and you end up with broadband that can get really close to the end user without busting the business case.

 The really cool thing about these new access devices (we almost hate to call them DSLAMs or BLCs) is their flexibility. All of the vendors we’ve spoken with recently are starting to ship their hardened mini-DSLAMs with ADSL2+ chipsets. Get the DSLAM within 4,000 or 5,000 feet of the user, and this can give you enough bandwidth to provide an MPEG-4 HDTV stream to the end user – something you might not be able to do with a larger BLC or a central-office-based DSLAM. Get even closer, and you can support a standard MPEG-2 HDTV stream.

 These line-powered DSLAMs are also designed to be upgraded to provide direct fiber-to-the-user connections. In most cases, a service provider can even maintain the line power while upgrading – so there’s a clear path from copper- or fiber-fed ADSL services today, to fiber-fed ADSL2+ higher bandwidth services in the mid-term, and on to a truly end-to-end fiber service in the future. That’s the kind of flexibility we expect any carrier can agree on.