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Comment by TrainedMonkey | Hacker News Reader

"In contrast, XG-FAST uses an increased frequency range up to 500 MHz to achieve higher speeds but over shorter distances. Bell Labs achieved 1 Gbps symmetrical over 70 meters on a single copper pair. 10 Gbps was achieved over a distance of 30 meters by using two pairs of lines (a technique known as “bonding”). Both tests used standard copper cable provided by a European operator."

30 meters with bonded pair for 10 Gbps. While this is pretty cool, due to distance limitation we are not getting telephone line modems that can outstrip fiber optics.

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> While this is pretty cool, due to distance limitation we are not getting telephone line modems that can outstrip fiber optics.

From the article:

"XG-FAST can help operators accelerate FTTH deployments, taking fiber very close to customers without the major expense and delays associated with entering every home."

So you actually are getting a modem, hooked up to your telephone line, that goes up to 70m over telephone cable to the street, and then fiber the rest of the way. Makes a lot more sense than literally doing fiber to every home.

> So you actually are getting a modem, hooked up to your telephone line, that goes up to 70m over telephone cable to the street, and then fiber the rest of the way. Makes a lot more sense than literally doing fiber to every home.

This is exactly how AT&T Uverse works in brownfield retrofits.

Much more than 70 metres typically.

I've seen this kind of setup in Japan more a few years ago, with vsdl as the technology for "the last meters": fiber optic was used by service providers down to neighborhood/building concentrators, and then the signal was carried over phone copper lines down to the office. We had a vdsl modem there, instead of a fiber one (I've seen those as well for business and homes).

Yeah it's still extremely common in Japan in anything that's not a new construction, they call it "mansion type". Supposedly up to 100 Mbit/s.

Afair, we had close to 100Mbit/s on our lines. The building wasn't very old, apparently we had good copper wires (I can't comment on the average quality of those across the country, but knowing Japan, it should be good).

I'm not sure how distances like 70 and 30 meters are actually useful. In my home there is certainly more than 30 meters of cable between phone socket and phone company's junction box in the basement, add another 10 meters from this junction box to where the cable actually enters the building and then at least 20 to actually get to the street.

This is for Fibre to the Curb, Fibre to the Cab (junction box ) is what is more commonly used and you can already get plenty fast enough bandwidth for consumer's with VDSL or SDSL at that range.

Btw Cab is UK tlco slang for it not sure what the USA Telco term is

How is fiber to the curb that helpful though? Why not just run it up and put the box on the side of the house like they currently do? This requires an extra modem.

much shorter run of copper so you can get faster speeds

So do you install a router on the sidewalk?

I think we call it Fiber to the Node.

Hardly. You are forgetting that most people's copper cabling is degrading quite rapidly or is already of very poor quality. Furthermore the number of nodes required on the street due to the 70m limitation would be a lot higher than with FTTP.

Exactly - this changes nothing. You'd still be paying workcrews to go street-to-street digging things up and running things through conduit.

At the point you're doing that, the marginal cost of getting them there is much higher then the cost of the equipment or cabling they'd be installing.

Running cable on poles or pulling it through conduit is much, much, much cheaper than fiddling around in someone's attic or crawlspace. The appointment has to be scheduled (i.e., the homeowner has to be there), you have to worry about the three hundred pounds of boxes they've got stored in the way, the crawl space or attic may be brutally hot or cold, have wasps, raw sewage, mud, or any number of other hazards. It's a slow and expensive job.

Not to mention legal hooplah and potential billing. Digging up the streets requires permission from the city, and maybe you send them a bill for some of your services.

Digging up people's front lawns requires permission from every homeowner, and if you are offloading cost you have to bill each homeowner...

You have to have permission from the home owner to switch them over from ADSL to VDSL and to give them a new modem. Here in Australia the plan was to run Fibre to the outside wall termination point on each person's house by default (opt out). Then someone comes shortly after to patch it through the wall etc if and when the customer wants it. There was no legal hooplah at all.

FTTdp is the technical term. It makes a lot of sense, especially if the telco rolling it out has ownership and maintenance of both the copper and fibre end.

But none of this would make sense or is in any way indicative of the pile of shit the coalition is set to be responsible for here in Australia, lest anyone think that.

> While this is pretty cool, due to distance limitation we are not getting telephone line modems that can outstrip fiber optics.

I doubt anyone is under any illusions that the copper is going to outstrip fiber. However, it is still an important result: There are many places that are stuck with old-fashioned twisted pair and it takes literally an act of gov't to lay down fiber. Rather than leaving that population out in the cold, this result gives hope that they may have cutting edge connectivity.

The real issue is commercializability, which has not been Bell's traditional strength.

Not to mention the fact that telephone lines are bandlimited at about 3000 Hz.

That only applies to voice calls, not DSL.

It applies to any call outside of the local loop. From the dsl wikipedia entry:

Because DSL operates above the 3.4 kHz voice limit, it cannot pass through a load coil. Load coils are, in essence, filters that block out any non-voice frequency. They are commonly set at regular intervals in lines placed only for POTS service. A DSL signal cannot pass through a properly installed and working load coil, while voice service cannot be maintained past a certain distance without such coils. Therefore, some areas that are within range for DSL service are disqualified from eligibility because of load coil placement. Because of this, phone companies endeavor to remove load coils on copper loops that can operate without them, and by conditioning other lines to avoid them through the use of fiber to the neighborhood or node

It does apply if you've got a pair gain system sitting in the middle, but you're essentially right.

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