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I was reading a similar question about cables here which claimed the max length you'd be able to use a CAT5 ethernet cable at would be 2.5km. Is there a rating of ethernet cable that would work well up to 5km? It looks as though fiber optic is used frequently for super long distance however I don't think that will work in my case as I'm unsure how the laser that produces the light impulse will fair under conditions. Additionally to communicate up to 5km would I need a special transmitter? And is the limiting factor noise, latency or something else?

I apologize if my questions are self evident but if I try to follow other sources from the initial link I quickly get lost.

Thanks for the help!

haxonek
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    maximum supported length is 100 meters.....https://en.wikipedia.org/wiki/Category_6_cable#Maximum_length – Moab Mar 13 '19 at 02:19
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    *the max length...a CAT5 ethernet cable...would be 2.5km*... Go back and read that a bit more closely. It says Ethernet over **coax**. – I say Reinstate Monica Mar 13 '19 at 02:20
  • Maximum supported length is 100m per segment. Then you need a router, repeater, etc. Cant remember how many segments you can have. Still don't think you'd get 2.5km. – Scottie H Mar 13 '19 at 03:13
  • @TwistyImpersonator I apologize then, I meant over coax cable. Is there a type of cable that will allow for more than 2.5km though? Perhaps using a thicker gauge of copper? Or is the only way forward with an intermittent router? – haxonek Mar 13 '19 at 03:30
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    @ScottieH: With switched Ethernet, as there is no collision detection anymore, I'm not sure why a router would be necessary – so I would guess infinite as long as you keep stacking repeaters (or ordinary switches). – u1686_grawity Mar 13 '19 at 06:05
  • Coax might be better for signal attenuation but there are no standards for fast modern ethernet that use coax cabling. At a high enough frequency (which this might be) everything is just bad coax. The advantage of twisted cabling is both sides of the pair are equally sized bad coax so they tend to get the same interference which cancels out when the difference between sides of the pair is measured. I don't think thicker cabling will help the signal quality in any important ways. – davolfman Feb 27 '23 at 20:38

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Some of the Ethernet over single-mode fiber optic cable standards can reach 10km (e.g. 1000BASE-LX10), and some nonstandard but multi-vendor interoperable conventions claim distances up to 70km (e.g. 1000BASE-ZX).

If you want to do Ethernet over more than 100m distance, you shouldn't use copper, you should use fiber. For in-building runs (say 300m) you can use multi-mode fiber, but for longer runs between buildings (or between cities) you should use single-mode fiber.

Spiff
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