Optical fiber and DSL find a meeting place

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Optical networks everywhere? The savviest vendors know this isn't practical. So they're moving to secure relationships that will let them play a part in the hybrid high-speed networks that even new local service providers are building.

A good example is Quantum Bridge Communications, the first vendor out of the gate with product and customers in the new generation of passive optical networking (PON) gear. On Monday, Quantum Bridge announced what it calls the second phase of its Access Alliance Program. The first phase dealt with makers of integrated access devices for customer premises. This second phase involves perhaps an even more important group: makers of termination gear for the hot multi-tenant unit (MTU) market.

In the company's announcement, four MTU vendors -- Tut Systems, AccessLan, Copper Mountain and Accelerated Networks -- signed on to make their equipment interoperable with Quantum Bridge's QB5000 optical access switch and to co-market to MTU service providers.

What's interesting here is the breadth of the market Quantum Bridge is trying to address. Often optical equipment vendors tout their ability to foster user-to-network interfaces such as Gigabit Ethernet, optical lambdas and other ultraband technologies.

But in briefings about the new MTU alliance, Quantum Bridge officials go immediately to a lower common denominator. Many, if not most, office buildings don't have enough internal fiber or Category 5 cabling to support native broadband services all the way to the tenant suite or desktop. Instead, the folks at Quantum Bridge note their MTU partners' support for DSL over Category 3 wiring. After all, DSL isn't just a network service provided publicly by carriers, it's a technology that can just as easily -- perhaps more easily -- be used within a facility for private purposes without the barriers often found in telco copper loops.

There's an irony here. PON vendors such as Quantum Bridge are sometimes superficially viewed as the anti-DSL crowd. They believe that fiber is the only long-term solution to the challenge of the public edge network, and that it should be built deep into residential neighborhoods and office parks with electronics removed and traffic shipped "passively" back to concentration points further upstream. They view central office-fed DSL as a service that will fall prey to its typically asymmetrical, sub-T-1 limitations, eventually maxing out below users' needs, the way ISDN essentially has.

But in-building, Quantum Bridge says the company and its partners can achieve SDSL or VDSL two-way high speeds at multiples of T-1s for each subscriber. The Access Alliance program is also careful to mix scaling options, with the four MTU partners providing anywhere from 12 to 72 ports of DSL connectivity in-building and T-1 to OC-3 links on the trunk side.

One thing that Quantum Bridge does have left to figure out is what precisely to do about metro Ethernet connections for those carriers and users positioned to take advantage of them. It's basically a build, buy or partner decision. Co-founder Jeff Gwynne says that Quantum Bridge could develop a Gigabit Ethernet connection for the box internally, but for multiple 10/100 ports, "it's a question of how many physical interfaces we're going to put on our device."

There's obviously more "phases" of the Quantum Bridge alliance program coming, so we'll see. More information about this program is available on Quantum Bridge's site.

This story, "Optical fiber and DSL find a meeting place" was originally published by Network World.

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