Copper vs Fiber

In the networking world, there are two distinctive kinds of communication mediums as far as last mile connectivity is concerned.

Copper based networks

Transmission using copper based networks works on the principle that dual copper pairs work in twisted pair forms to transmit data from one point to another. These involve transferring of data from one point to another using existing local telephone networks. The term most commonly referred to this technology is "Digital Subscriber Line" or DSL.

An explanation of DSL Technology from Wikipedia is as follows:

"Digital Subscriber Line (DSL) is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL uses a second, higher frequency band (greater than 25 kHz) above the low frequency regime (5 kHz and below) used by voice communications. On customer premises, a DSL filter is installed on each outlet for telephone handsets to remove the high frequency band, eliminating interference with the operation of the telephone set, and enabling simultaneous use. "

Suffice to say, that the maximum speed generated in worldwide over for copper based twisted pair networks is 1 Gbps.

However, this speed has a distance limitation of 100m cable length, after which the signal has to be repeated using a switch or power over Ethernet (POE) adaptor.

Despite this, it is unlikely that copper based networks will eventually be replaced completely by their fiber optic counterparts. This is evident through the research of Nokia Siemens Networks, who proved that the use of an innovative concept could expand existing copper based networks. This concept is called phantom dsl.

Phantom dsl uses the creation of a virtual/phantom channel to supplement the dual twisted copper wires existing as the base for the copper network.

Using this technique, a speed of 825 Mbps was recorded over a distance of 400 m, with a sustainable speed of 750 Mbps over a distance of 500m.

This represents a huge breakthrough for copper networks, since the traditional distance limitation of 100m was considered to be one of the main factors by which fiber optic networks were introduced to replace copper based transmission mediums as the last mile technology of choice.

Fiber Based Networks

Fiber-optic lines are strands of optically pure glass as thin as a human hair that carries digital information over long distances. They are arranged in bundles called optical cables and used to transmit light signals over long distances.

A single optical fiber consists of the following parts:

• Core - Thin glass center of the fiber where the light travels
  
• Cladding - Outer optical material surrounding the core that reflects the light back into the core
  
• Buffer coating - Plastic coating that protects the fiber from damage and moisture
  

Hundreds or thousands of these optical fibers are arranged in bundles in optical cables. The bundles are protected by the cable's outer covering, called a jacket.

Optical fibers come in two types:

• Single-mode fibers
  
• Multi-mode fibers
  

Single-mode fibers have small cores (about 3.5 x 10-4 inches or 9 microns in diameter) and transmit infrared laser light (wavelength = 1,300 to 1,550 nanometers).

Multi-mode fibers have larger cores (about 2.5 x 10-3 inches or 62.5 microns in diameter) and transmit infrared light (wavelength = 850 to 1,300 nm) from light-emitting diodes (LEDs).

Some optical fibers can be made from plastic. These fibers have a large core (0.04 inches or 1 mm diameter) and transmit visible red light (wavelength = 650 nm) from LEDs.

Principle of Fiber optics

The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection.

Because the cladding does not absorb any light from the core, the light wave can travel great distances. However, some of the light signal degrades within the fiber, mostly due to impurities in the glass. The extent that the signal degrades depends on the purity of the glass and the wavelength of the transmitted light.

So, which technology is better in terms of last mile connectivity? Both have their pros and cons. I'll leave it to you to decide.