[cm2187]

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.

[midasuni]

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)

[anonymousiam]

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...

[repiret]

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, there must be some other reason to not run fiber for new installations.

[Aloha]

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.

[rodgerd]

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.

[Aloha]

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

[robocat]

I was initially a skeptic of the cost of Fibre-To-The-Premises, but in hindsight for New Zealand (≈Oregon) I think a national rollout of fibre was very effective[3][4].

AFAIK fibre is more resilient to catastrophes (like earthquakes[1][2] in Christchurch or California), and having a high speed residential fibre network definitely helped during Covid.

I am uncertain what you mean by “efficient”. Perhaps link to something that backs up your opinion?

[1] https://az659834.vo.msecnd.net/eventsaircancprod/production-...

[2] https://www.researchgate.net/profile/Sonia-Giovinazzi-2/publ...

[3] https://news.ycombinator.com/item?id=29791864

[4] https://news.ycombinator.com/item?id=25339491

[rodgerd]

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.

[LargoLasskhyfv]

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...

[GreyStache]

Regarding the termination: our local fiber provider handles the termination with some optical precision connector (forgot the name). Both to the sunken-in-sidewalk multiplexer and in the home to the optical termination point (both gpon). So for mass deployments fiber connections do not require fibre welds are not required.

I have to see it play out in practice and I'm not a fan of the idea that one telco controls controls (ie stifles competition) in a gpon scenario. The conduit has recently been placed in our street, so "soon"...

[Aloha]

I'm still a fan for cost reasons of FTTN, because I think with Coax in the last mile, you can deliver fantastic performance, so long as you're not also trying to delivery video too.

Furthermore if you actually run Coax in duct for buried circuits, its easy to replace with fiber later.

[bayindirh]

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 and use existing equipment (which can handle 350mpbs), rather than bringing in fragile fiber into the home.

[toast0]

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.

[jcrawfordor]

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 <100 customers) requires an OLT which is relatively large and needs separate power provisioned. You can put OLTs in serving area cabinets but this is costlier compared to cable equipment.

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.

[upofadown]

... also lightning strikes hitting the ground somewhere in the area. That can induce large voltage differences between the power grounds on the buildings. The voltage difference might be large enough to arc across any isolation provided by the physical network implementation.

[kevin_thibedeau]

My neighbor's house was hit by lightning last year and it took out the ethernet ports on two of my devices. Nothing else was affected though. Those devices still work. They're on a PoE switch (though not using PoE) so that may have been part of the cause.

[madaxe_again]

Then you just install a lightning arrestor on your comms circuit - I have a mast way up the hill to provide our connectivity here, and use one on the Ethernet line down to prevent issues (like a house fire) from a strike.

[dboreham]

There's really no "just" concerning lightning protection. You can just add some protection, to code or above, but it may not work. Nature can be unforgiving.

[Aloha]

You have to assume a direct hit by lightening will fry your hardware, period, full stop - proper grounding and lightning protection however will mean that the hardware does not catch fire.

[Animats]

There are lightning protectors that will absorb a direct lightning strike. Most antennas on hilltops and tall buildings have them. They take lightning strikes routinely. Here's some ARRL material on lightning protection.[1]

It's not difficult, but it's not miniature. A classic design was a soup-can sized device with a coax connector on each end and a hulking big ground connection on the can. Inside was a spark gap with dime-sized silver contacts, and a few turns of copper busbar as an inductor to smooth out the spike that got past the spark gap. That goes where the cable enters the building. Similar units today tend to be smaller. There will still be serious metal boxes.[1]

You need a serious ground. As in hulking big copper cable to a long ground rod. Grounding to a pipe is no longer allowed; there might be plastic pipe somewhere in the system, either now or in the future.

The next stage is a "central office protector". This is a gas tube with three terminals - both sides of the line, and ground. So it's an enclosed spark gap in an inert gas. An overvoltage will ionize the gas and short it to ground. Telco central offices have one of those on each line. They're plug-in devices that sometimes have to be replaced.

There's a lot of obviously fake stuff on eBay and Amazon in this area. 2D logos superimposed on curved surfaces, even. There's a standard, UL 497B. If it doesn't have that certification, don't buy.

[1] https://www.polyphaser.com/search?Category=Data+Surge+Protec...

[1] http://www.arrl.org/lightning-protection

[Aloha]

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 the 16-20ga wire in the cable itself at the first point its near a ground. Carbons, Glass Tubes, and other similar hardware will protect you in the event of a nearby strike (like to a lightning rod on a tower, or building) - but wont save you if the infrastructure is struck itself.

Generally the point of lightning protection systems is to well ground the tower, to draw the lightening away - so the tower and grounding system can protect the equipment - that isn't a direct strike by what I'm saying here - a direct strike would be if it struck the antenna itself.

Thats the perspective I have from cleaning up from strikes at well grounded and protected tower sites.

[Animats]

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 flickering. I've seen that in Florida.

Worst case is probably is an AM broadcast station where the tower is isolated from the ground at the base. WSM in Nashville TN is like that. They had a pipe ground vaporized and windows blown out in a lightning strike in December 2019. They lost the tower lighting and some transmission components were damaged, but they apparently stayed on the air.

The Empire State Building takes about 25 lightning hits a year. I wonder what their lightning protection looks like.

[aidenn0]

Magnetic coupling removes any issues with potentials, and if it's not AC at the same frequency as what's in the wall, the phase is irrelevant.

[willglynn]

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 the pair on the secondary side, no problem. If a wire pair suddenly measures a thousand volts across… well, Ethernet transformers are typically wound 1:1.

_Ideal_ magnetic coupling removes issues with potentials. Ideal transformers behave as above, but real transformers have parasitic effects, particularly winding capacitance. Fast transients (including ESD) can and do capacitively couple across the transformer from primary to secondary.

Magnetics are important but do not solve the problem on their own. It is possible to design and manufacture electrically robust copper Ethernet systems – for a given definition of robustness (typically defined as passing some specific EMC test) – but even then real world electrical faults can and do destroy robust Ethernet systems. Fiber has none of these concerns.

[aidenn0]

All very true; good clarifications. In context my point was that it would be totally safe to run a copper Ethernet cable between two houses on separate electrical grids (or even an un-earthed battery powered computer).

[Aloha]

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 fashioned ground return systems.

Indeed, measurement of voltage and continuity of T-G and R-G is a standard way to check for faulty cable

[bcrl]

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.

[dekhn]

Any long run like this would use optoisolaters.