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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

#191

Post by anonymousiam »

midasuni wrote: post #89
cm2187 wrote: post #87

Earlier quoted context omitted.

Fiber doesn’t conduct electricity, a wire does. I remember reading somewhere to be careful with running a wire over any long distance between two houses that are not connected to the grid with the same meter. Something to do with phase or different potential, can’t remember, but the point was it could fry your equipment. Fiber sounds a lot safer to me.

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)

Lots of comments about lightning, but I believe you are referring to a "ground loop" where the ground/neutral at one site is offset from that of a different site tens or hundreds of meters away. This is why all commonly used RJ-45 Ethernet connections use differential signalling and have the tx/rx pairs isolated by transformers. (Note that PoE Ethernet can still create similar problems if one is not careful.)

Here's a relevant news article about a lawsuit related to this phenomenon:

https://easyreadernews.com/edison-stray-voltage/

https://www.dailybreeze.com/2013/03/19/redondo-beach-woman-a...

https://www.nydailynews.com/news/national/woman-wins-4m-verd...

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

#192

Post by rasz »

transistor-man wrote: post #75

Awesome project! This would be fairly great fit for underwater UAV's, or like security camera way out on the edge of property. May be a good idea to post on ardu-sub related discussion forums. I'm not aware of an off the shelf module that's point to point ADSL, almost every modem is intended to yell at a ADSL / ADSL2+ host. Did you run into any issues with consumer-grade gigabit switches negotiating 10Mbit?

ROV community zeroed in on hacked homeplug devices long time ago. $30 a pop 100Mbit 1km links.

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

#194

Post by rodgerd »

Aloha wrote: post #172
rodgerd wrote: post #169

Earlier quoted context omitted.

https://www.chorus.co.nz/tools-support/broadband-tools/broad... New Zealand has fibre to the home for the majority of a country the side of the eastern seaboard of the US, with only 5 million people, and a lower per-capita GDP. It's doable. It's just a question of wanting to.

Its just not as efficient, you can deliver similar classes of service by HFC networks.

Australia and New Zealand have helpfully agreed to provide a case study in which works best. Mixed fibre and copper in Australia is slower and ended up costing dramatically more than it was supposed to.

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

#195

Post by zbrozek »

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?

Yes.

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

#196

Post by LargoLasskhyfv »

Aloha wrote: post #172
rodgerd wrote: post #169

Earlier quoted context omitted.

https://www.chorus.co.nz/tools-support/broadband-tools/broad... New Zealand has fibre to the home for the majority of a country the side of the eastern seaboard of the US, with only 5 million people, and a lower per-capita GDP. It's doable. It's just a question of wanting to.

Its just not as efficient, you can deliver similar classes of service by HFC networks.

I think it's just inertia. At higher speeds you have to do so much signal processing going over copper, that it iss costing more and more energy compared to optical. Which is limited to 2.5 Watts per port and end of the fiber, at least in common prosumer facing gear. While you can push up to 80KM(or meanwhile even more!) in one run with such stuff, depending on the used fibre and wavelength.

Speaking about optical modules in this formfactor: https://en.wikipedia.org/wiki/Small_form-factor_pluggable_tr...

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

#198

Post by ajsnigrutin »

vicek22 wrote: post #43

- 1km of fiber optic cable - https://www.amazon.com/Jeirdus-Launch-Singlemode-Measuring-O... - 1Gb modem - https://www.amazon.com/TP-Link-Ethernet-Converter-Multi-Mode... The price for two modems and the cable is just under $120

I think this is more a usecase for places where you already have a copper cable available (eg. telephone cable between buildings). If you have to dig and pull a new cable, doing fiber is the only logical choice now, but the price for all that is way way above $120.

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

#199

Post by bcrl »

Animats wrote: post #161
Aloha wrote: post #156

Earlier quoted context omitted.

Well, Howdy! I'm a licensed radio amateur since 1996, I've spent about 20 years working in the cellular/telecom/two way radio industry, and I've done Motorola R56 inspections (as well as other proprietary grounding standards). I respectfully disagree, a direct lightning strike almost certainly will take out gear at a cell site, even when properly grounded. Similarly a direct strike to telco cable will certainly fuse…

Yes, few antennas really need to remain operational against direct hits. Nor do they usually need to be the highest thing on the tower. Data cables aren't usually up that high, fortunately. Power cables, though, are. In some areas high tension towers carry a ground wire between the peaks of the towers for lightning protection. It's impressive to see those systems take repeated direct hits without the lights even flic…

Clearly you have never seen a phone line fried by a direct lightning strike before: the cable vaporizes and blows up the ground over top of it. Direct strikes are rare enough that most people will never see them. On overhead lines the neutral and communications strand are grounded and will take most of the strike over the twisted pair communications cable. Underground cables have some benefits by being in non-conductive conduit, but none of that matters if it's a direct strike. All insulators will break down in a strong enough electric field.

There's also the issue of ground bounce. A lightning strike near a house will feed back into the telecommunications and power equipment via the ground rod/plate. I've had experience with plenty of modems getting fried over the years. Some places are just lightning magnets.

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

#200

Post by bcrl »

Aloha wrote: post #136
willglynn wrote: post #102

Earlier quoted context omitted.

I'd like to add a few asterisks: Magnetic coupling removes issues with potentials _up to the dielectric breakdown voltage_. Ethernet magnetics are considered high potential components, and even the entry level options will isolate at least 1.5kV, but fault events often exceed that figure. Magnetic coupling removes issues with _common mode_ potentials. If the + and - side of a pair are both a thousand volts away from…

Inductive pickup (foreign voltage) from even fairly long runs (20kf +) of well maintained copper is usually much less less than half a volt, measuring either T-R, or T-G/R-G. It's supposed to be floating to ground - nothing on a twisted pair should be ground referenced, if you do have voltage to ground, you have a short. If it was not floating, you'd get atmospherics, hum, and other issues that you saw in old fashion…

Unless the telco cut the outer shielding on the twisted pair cables everywhere a terminal was installed. That was one of the remediations the incumbent had to undertake here when they started deploying 50Mbps VDSL2 FTTN service. Oops.
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