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Comment by zrm | Hacker News Reader

> If you're connecting a single device, why the hell would you use that when you could slap a copper SFP or SFP+ module in the switch's cage and run a cable?

The problem to be solved is that you want to be able to put fibre inside the walls of the building instead of copper. Running a new cable to the switch closet is the thing to be prevented.

But if the wall jacks are fibre then you need some economical way of hooking them up to every printer and single-purpose device with a network port. If you have to buy another $100+ switch just to get from fibre to copper even when there is only one device near that jack, people aren't going to go for that.

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> The problem to be solved is that you want to be able to put fibre inside the walls of the building instead of copper. Running a new cable to the switch closet is the thing to be prevented.

...why would you ever not run copper alongside fiber for new construction? If nothing else, PoE is extremely useful, and nothing says that you actually have to connect all of that copper cable to your switch... you can connect it as-needed. I also can't imagine that most refits only have room for exactly one cable in their conduit. [0]

I'd expect to hear the sort of plan you propose from a PHB or Highly Paid Consultant, not someone who actually has had to use that sort of configuration.

Regardless, the scenario you're now proposing is one where noone other than a PHB would use that Amazon Special that you linked for media conversion.

[0] If there's no conduit and cables are all flopping around in the wall, then there's even more room for cabling.

The original problem was that everyone runs copper instead of fibre because there are too many existing devices that only have copper. Running both everywhere would require you to buy and terminate twice as much cable as you expect to use, which leads people to running only copper again.

If you chose PCs to begin with that come with fibre ethernet or put quality cards in the ones that matter then you could make fibre the default instead of copper. Until you have a number of devices like printers or VoIP phones or Raspberry Pis that have no need for 10Gbps or even 1Gbps connectivity, they just need a way to be plugged in at all. If you need to add $100+ in conversion expense to each of those devices, you're back to using copper by default.

> Running both everywhere would require you to buy and terminate twice as much cable as you expect to use...

Ah. Let's play with that logic a bit:

"Running Ethernet cabling everywhere would require you to buy and terminate far more than twice as much cable as you expect to use. Just run power cables and wire up one extra outlet for a HomePlug in each room.".

Yeah, that checks out. "Powerline Ethernet" devices are actually pretty good these days, and are right around your magic price range... Amazon has them at ~13 USD per unit. [0] Why would anyone bother running a second cable to each room? Thirteen bucks per room has to be way less than the materials and labor cost for the cable run. Doing anything else is, like, really stupid. Don't you agree?

Anyway. You expect to use the cabling that you plan to install... plus some extra for screwups, man.

[0] <https://www.amazon.com/Linksys-PLEK500-Homeplug-AV2-Powerlin...>

Running a new cable is easy. You just use the old cable to pull the new cable. You can run composite cable if you desire copper, fiber and power.

> You can run composite cable if you desire copper, fiber and power.

Oooh. Cool.

By "power" do you mean 120/240VAC, or do you mean much lower voltage DC? I've found some Belden cabling that I think provides mains power and Ethernet, and I've found fiber cabling that I guess carries lower voltage DC, but am having a tough time finding a cable that combines fiber and copper data with mains power. Do you have an example of such a cable handy?

(Full disclosure: I'm refusing to spend more than like five minutes on the search... so I might have been able to dig up examples of such a cable.)

Which is why people run only copper because that costs less than running multiple types of cable everywhere when most drops only have one device, and then pull fibre through using the existing copper cable in the rare instances where they find a need for 40Gbps or more.

But then the copper gets used for 10Gbps connections instead of fibre because it's what's already in the building.

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