My ISP says they bring optical fiber to their junction box outside and they bring the copper cable inside from the junction box. And they're promising a symmetrical bandwidth with a speed upto 50MBps. Is this even true? Can we really do that optical to copper conversion and get that speed?

I've gone through the internet searching for the answers but I've not come across this conversion anywhere. Please help me out here.


2 Answers 2


Fiber media converter is a small device with two media-dependent interfaces and a power supply, simply receive data signals from one media, convert and transmit them to another media. It can be installed almost anywhere in a network. The style of connector depends on the selection of media to be converted by the unit. The most common being UTP to multimode or single mode fiber. On the copper side, most media converters have an RJ-45 connector for 10BASE-T, 100BASE-T, 1000BASE-T and 10GBASE-T connectivity. The fiber side usually has a pair of SC/ST connectors or SFP port. Media converters may support network speeds from 10 Mbps to 10 Gbps, thus there are Fast Ethernet media converters, Gigabit Ethernet media converters, and 10-Gigabit Ethernet media converters.

Fiber media converters change the format of an Ethernet-based signal on Cat5 into a format compatible with fiber optic cables. At the other end of the fiber cable run, a second media converter is used to change the data back to its original format. One important difference to note between Cat5 and fiber is that Cat5 cables and RJ45 jacks are bidirectional while fiber is not. Thus, every fiber run in a system must include two fiber cables, one carrying data in each direction. These are typically labeled transmit (or Tx) and receive (or Rx).

Illustration: enter image description here

Media converters may be simple devices, but they come in a dizzying array of types. Newer media converters are often really just a switch. Smaller compact switches offer various interfaces on both RJ45 and fiber, which gives a great overall platform to convert from.

Source: https://community.fs.com/blog/how-fiber-media-converter-works.html

  • That's some good information. Can you elaborate a bit on the bandwidth while converting?? Will it decrease or remain the same?
    – iamgr007
    Commented Jun 6, 2019 at 13:34
  • 1
    @Nuwanda there's no loss in the bandwidth, when converting. New equipment will switch at line speed.
    – Cow
    Commented Jun 6, 2019 at 13:39
  • Alright! Thanks for the clarification
    – iamgr007
    Commented Jun 6, 2019 at 13:42
  • are bidirectional while fiber is not That is wrong. There's en.wikipedia.org/wiki/Gigabit_Ethernet#1000BASE-BX10 to allow the use of a single strand of fibre (and there's similar variants of 40G Transceivers mapping their 4 lanes of 10G to different wavelengths). 1000BASE-BX is commonly used in FTTH deployments. Commented Jun 6, 2019 at 22:16

"copper" is a rather vague term. it could refer to Twisted pair Ethernet, docsis (cable TV coax), various types of DSL, or various legacy telco technologies.

But yes there are plenty of technologies that can deliver 50 megabits per second or more over shortish distances on various types of copper cable. The most obvious to us non-ISP folks being twisted pair Ethernet which commonly delivers gigabit speeds at distances up to 100 meters and can in principle deliver 10Gbps. ISPs may preffer DSL or DOCSIS though because of longer ranges and/or the ability to reuse existing infrastructure.

How best to provide "fiber" Internet services to homes and small business premises is something of an open question. Many providers are reluctant to install fiber right into the customer premises due to concerns about installation costs/difficulties (you can't treat fiber the way telco installers treat copper and expect it to work reliablly). Others believe that not taking the fiber all the way is a false economy that will result in expensive re-engineering as the demand for speed rises.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.