I hope that this is not an ignorant or misinformed question, I am new and I'm trying to learn more about internet provision.

I have read that DSL has a maximum distance of 18,000ft (or 5.5 Km) before a loop extender has to be established to keep the speed from degrading. What are cable and fiber optic's maximum distances before a loop extender must be established, if any? I have also read that fiber optic lines do not degrade over the distance between the ISP and the customer, is that true?

If I need to provide any more information to my question, just let me know and thank you.

  • This question is really far too broad to answer here. You need to edit to be more specific. Is it for ethernet your your business? If so, to which ethernet standard are you referring? The different fiber type and transceiver combinations will all have different limits. Please edit your question to be specific.
    – Ron Maupin
    Jul 16 '18 at 2:53
  • Fiber can reach and exceed 100 km, depending on the used technology.
    – Zac67
    Jul 16 '18 at 7:14

It varies massively depending on the media in use, and even the DSL use-case you're mentioning is going to be dependent on the type of DSL, bit rate and line quality.

In terms of fiber optics it's similarly variable. Older types of fiber running higher speeds might be limited to 20-25 meters maximum (..and even that's a terrible idea), while there are WDM systems that can push spans literally thousands of kilometers long if using appropriately doped fiber (ex: trans-oceanic cables).

Here is a decent article describing multi-mode fiber, which is often used for short-distance runs within facilities like data centers. The corresponding single mode article (single mode can be used within facilities and is also a better choice between sites) also lays some useful basics out. The general article lays out some of the distance/speed records for long-haul WDM gear.

Ultimately, though, the real limit has more to do with what you're trying to transport. The problem of running optical to a terminal on the side of a residential installation is quite different than undersea cabling, and neither is very similar to running Ethernet within a data center.