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10mbps over 1km on a single pair of wires

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Re: 10mbps over 1km on a single pair of wires

#211

Post by jcrawfordor »

repiret wrote: post #135
midasuni wrote: post #89

Earlier quoted context omitted.

The biggest problem is lightning strikes hitting the cable. The phase wouldn’t matter - and even different earthing wouldn’t matter as long as you only connect any shield at one end. But fibre is so much more versatile if you’re running new cables (unless you want to run power)

Last summer the local cable company replaced all their cables in town in order to begin offering digital cable and internet service. I was flabbergasted that they they spent all that money on linemen but still ran coax rather than fiber. As far as I can tell talking to their linemen, its not even FTTN, just FTT-central-office. Assuming its not run by morons, which I'll accept is a bit of a stretch for a cable company…

DOCSIS is capable of 3gbps over coaxial cable and there is more room to improve, so fiber doesn't have a significant advantage in terms of possible bandwidth. Because DOCSIS was designed to operate on the cable network, which was designed to reach a very large number of homes, the architecture of the system tends to be more cost-effective than fiber. The fiber equivalent of a cable-like topology, and what is used by fiber ISPs, is PON, but PON is actually relatively limited in terms of both range and number of service points compared to DOCSIS on cable. A typical PON installation requires more field equipment to serve the same customers at the same rate compared to DOCSIS.

This is made worse by the issue of power distribution: the field equipment for DOCSIS consists of distribution amplifiers which are powered over the coaxial cable itself, allowing the battery-backed power supplies to be placed at convenient locations. There's not really any equivalent of this for PON, so extending PON networks beyond a single loop (depends a lot but typically a few KM and Another major factor is the customer premises: most homes already have coaxial cable distribution installed that is either compatible with DOCSIS 3 or can be made compatible with DOCSIS 3 by replacing the distribution amplifier or passive tap, which is a fairly cheap and fast operation. Installing PON to customers requires getting fiber to their house, and then either an outdoor ONT (troublesome from a maintenance perspective) and ethernet into the building or fiber into the building. The equipment here doesn't necessarily cost much but the labor of running new lines into customer homes is substantial and makes signing up new customers much higher-friction.

Most of the time when a cable provider upgrades to introduce DOCSIS 3 for digital voice and internet they aren't really replacing any cable anyway, just distribution amplifiers and nodes. The cost of this work is significantly lower than running new cable and it doesn't require new pole attachment agreements etc.

In general, in urban environments with existing cable TV plant there are few upsides to fiber. Urban fiber in existing areas is usually only cost effective when it's a new ISP competing with the cable company.

Finally, most DOCSIS networks are in a process of transitioning from CMTS (cable modem termination system, the upstream end) in the cable headend to a compact serving area CMTS at each amplifier point. This is called "Node+0" architecture, meaning there is a fiber node and then zero distribution amplifiers before the customer. One of the nice things about the cable "HFC" or hybrid fiber/coaxial network is that it is relatively easy to make this transition progressively as you sign up additional customers, since CMTS nodes have been made very small. PON is less forgiving this way and requires more up-front capacity planning, especially since network expansion means the permitting process on relatively large curb cabinets or enclosures.

Re: 10mbps over 1km on a single pair of wires

#212

Post by jcrawfordor »

unwind wrote: post #74
gandalfian wrote: post #70

I'm 1km of copper to green box, then fibre rest of way to telephone exchange. VDSL 40mb down and 6mbs up. That's on a 1980's buried copper cable.

Neat, but is that copper a single pair?

One catch is that ISPs rolling out VDSL, such as CenturyLink, are often using pair bonding. So despite a typical performance limit of 40/10, CL offers 80/20 in VDSL markets by taking advantage of the fact that homes are typically wired for two lines.

Re: 10mbps over 1km on a single pair of wires

#213

Post by hinkley »

jagger27 wrote: post #175
hinkley wrote: post #171

Earlier quoted context omitted.

Or a fat old conduit that you can run a new wire through...

I can't imagine a scenario where you already have a 1km long conduit that doesn't already have copper or fibre in it. Why would you choose to push a kilometre of brand new copper twisted pair line down an existing conduit just to squeeze 10 Mbps out of it? The hard part is already done and fibre equipment is pretty cheap. If the conduit already has a phone line in it that isn't being used, sure.

In the context of the current thread, I'd say that's fair. If you're talking urban infrastructure, my understanding is that things are good until the existing (fairly large) conduits fill up, and then everything stops until someone digs up the street for blocks and blocks.

Do you happen to know, for these long conduits is it typical to do a solid run or to put access panels at regular intervals? If you're running a new cable are you actually trying to run a 1km snake through a pipe, a 100m snake 10 times, 50m x20, or something in between?.

I've never seen anyone run a 1km cable, but I've seen buildings be rewired with tens of kilometers of new cables a couple times.

Re: 10mbps over 1km on a single pair of wires

#214

Post by fragmede »

Aloha wrote: post #188
xenadu02 wrote: post #181

Earlier quoted context omitted.

This sounds like post-hoc rationalization. I have Sonic fiber in SF. 1Gbps symmetric, over a "fragile fiber" run directly into my home. It works quite well. The drop cable is pre-made in standard lengths with weatherproof connectors. The glass is embedded in a large-ish diameter substrate that resists sharp bends naturally so the installers don't need to take special care to prevent losses, just don't try to force th…

Does Sonic own their own fiber network?

They own some fiber. They'll also sell you service using AT&T's fiber if that's what's there.

Re: 10mbps over 1km on a single pair of wires

#215

Post by DannyBee »

bufferoverflow wrote: post #173
DannyBee wrote: post #48

Earlier quoted context omitted.

The fiber is much cheaper because it's so much more common. For example: I/O fiber is about 0.10 cents a foot or less for 2 fiber cable. (12 fiber is only 20 cents a foot). OSP gel-filled direct burial is 0.55 cents a foot or less for 2 fiber cable. (12 fiber is only 65 cents). This is micro-armored OSP cable, resistant to chewing/damage as well. Basic 18 awg single pair shielded direct burial wire is about 0.80 cent…

Aren't you off by a factor of 100? Maybe dollars per foot, not cents per foot?

It's dollars per foot, yes. Honestly though, since they are all in the same relative scale, and the point is what was cheaper and by what percent, this feels like pedantry.

Put another way - outside of being technically correct, why does it matter to the point at hand?

Re: 10mbps over 1km on a single pair of wires

#216

Post by DannyBee »

xenadu02 wrote: post #182
Aloha wrote: post #142

Earlier quoted context omitted.

When everyone prices fiber, they fail to include the termination costs. How much are the termination costs on that fiber, per run? Also, you'd never install single pair direct burial, and almost never shielded (unless its audio and not phone type) - it'd be 4/6/12 pair direct bury gel-filled cable.

Besides what DannyBee says about termination being a lot cheaper and easier when you can tolerate small losses (which is most people): Big infrastructure often orders the cables pre-terminated, eg an ISP will order their arial cable with built-in termination at certain intervals. No muss, no fuss. You're right about single pair though. If you're putting in two strands might as well do 6. If you need 6 might as well d…

Yeah, from a cost/redundancy/etc perspective it rarely would make sense to run 1.

I will get pre-terminated for MTP runs, but not for anything else. Fusion splicing connectors just isn't slow (and if i need to go quick, i'll just splice a pigtail onto it until it fails)

I agree for redundancy, etc, better to just add more until loss-of-ROI occurs, but will say doing something for extra capacity for home users/even business users feels like massive overkill these days.

Even 2km 100G duplex transceivers for SMF are <$200 a piece now. Cost is dropping crazily fast. (bidi simplex ones now also exist on fs.com as of a month or two ago, but are still way too expensive)

Re: 10mbps over 1km on a single pair of wires

#217

Post by eru »

voakbasda wrote: post #81
eru wrote: post #36

Earlier quoted context omitted.

I don't think the wire itself would be the expense, but the laying of it?

The cost of laying wire is virtually the same as laying fiber, so the difference really comes down to the material costs. The only good reason to use wire would be existing installations, as you sidestep that cost entirely.

Whatever EUROCARE said about existing installations applies.

Though what I had in mind was that when I was handling optical fibre as a layman (we have fibre to the living room here in Singapore), that fibre is a lot more delicate, so would require a bit more care to handle than copper. But I guess that's probably not a major cost factor, if eg you have to dig a trench for your cable.

Re: 10mbps over 1km on a single pair of wires

#218

Post by toast0 »

Aloha wrote: post #138
repiret wrote: post #135

Earlier quoted context omitted.

Last summer the local cable company replaced all their cables in town in order to begin offering digital cable and internet service. I was flabbergasted that they they spent all that money on linemen but still ran coax rather than fiber. As far as I can tell talking to their linemen, its not even FTTN, just FTT-central-office. Assuming its not run by morons, which I'll accept is a bit of a stretch for a cable company…

Cost and Fragility. You can push around 1GHz of bandwidth on the normal hardline-feed line with taps system cable uses, each node is designed to pass by a certain number of households. Coax is.. cheap, forgiving, easy to terminate, and inexpensive to replace - Fiber is more expensive, unforgiving, and much harder to terminate.

When AT&T did a fiber overlay in San Jose (GPON), they had neighborhood cables that were factory terminated to go from wherever to each pole. The linemen had to setup the pulleys? and pull the cable through, and attach them, but they didn't have to terminate them. When they ran a line to my house, they did do a field termination, but it seemed like they had a tool and it went quickly (mine was the tech's first time, or at least pretty early, but it only took a minute or so).

Of course, for repair work, if a tree or something breaks a multi fiber bundle, splicing is going to be a lot harder than coax. Probably harder than traditional phone lines, but I think PON is setup so that you don't need to care which wire connects to which other wire, and if you do that for end-user traditional phone lines, you'll have a big mess, so you'd really want to match the wires up before you junction them. Coax is just one big wire, so way simpler.

Re: 10mbps over 1km on a single pair of wires

#219

Post by toast0 »

DannyBee wrote: post #179
jandrese wrote: post #97

Earlier quoted context omitted.

This product makes sense if you are reusing existing copper lines.

in which case unless you have 18awg copper lines around, you can't do 1km :) I would be shocked if anyone has those. Maybe alarm wire I guess?

I've got a 3 pair run[1] to my gate with a keypad gate controller. Two pair are used for voice communications, and one pair is idle. The gate controller has 10 base T ethernet (for management), but you need two pair, and it's maybe a touch outside the distance spec for 10baseT. I'm not quite ready to spend $350 to get it on ethernet though.

[1] Actually, it's 4 pair to an in-ground junction box, where it splices to 3 pair to the gate controller. For $350, I have maybe some other other options around the junction box (I've already got some passive 10baseT single pair devices, but they don't work at the full distance. Probably would work at the junction box, if I had a powered ethernet switch there, but I need weatherproofing.

Re: 10mbps over 1km on a single pair of wires

#220

Post by bayindirh »

xenadu02 wrote: post #181
bayindirh wrote: post #158

Earlier quoted context omitted.

Our telco converted all its infra to FTTN via fiber. So, I've actually have fiber connection up to the front of my building, then it's terminated and distributed via VDSL to the street. I have a 50/8 mbps connection at home and, it gives all the performance it can give. The telco keeps the speeds a bit higher to handle VDSL overhead, so we have a real 50/8 mbps IP connection at premises. I'd rather not rewire my home…

This sounds like post-hoc rationalization. I have Sonic fiber in SF. 1Gbps symmetric, over a "fragile fiber" run directly into my home. It works quite well. The drop cable is pre-made in standard lengths with weatherproof connectors. The glass is embedded in a large-ish diameter substrate that resists sharp bends naturally so the installers don't need to take special care to prevent losses, just don't try to force th…

> This sounds like post-hoc rationalization.

Uhm, no, it's not.

I'm using a 1gbps symmetric connection at the office, for the last decade or so. The network speed is limited by my NIC and the cabling to the switch. The network at the office has more bandwidth (we're the network backbone).

We have fiber ran into our apartment buildings. My apartment's termination box is at the wall across my flat door. On the other hand, the speed I can get from that fiber is not higher than the current VDSL offerings, and they both cap at 100mbps downstream (upstream is probably limited at the same speeds with VDSL). Since the FTTN box is also outside, the speeds and stability from that VDSL connection is rock solid.

For no apparent speed advantage, I need to terminate a thick fiber, and need to run it in the open across the house, drilling walls in the process, or move my house's whole internet infrastructure near it. Both are illogical given the floor plan of my house.

Then comes the equipment part. Again, I'll need to change my core router at home and change everything (I have a mesh network at home), or cascade it to ISPs fiber router, which is another box, more cables, and more management. If the ISP allows me to use my own router, I'd need a media converter from fiber to copper. Which's again more cables, more boxes, more management.

As a result, I'd rather use my house's in-wall cabling to get the speeds I'm happy with instead of getting a shiny (pun intended) technology with no speed advantage.

If the speeds offered here changes over time, I can re-evaluate my choices, but as the xDSL technology gets better, I'm guessing that it'll keep the same speeds with fiber offerings, at least for residential stuff in my area. So, I project that I can upgrade my network speeds at least for a decade without changing my network equipment or cabling.

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