Fibre Optics

How Do Fibre Optics Work?

Fibre Optic Cabling Compared to Copper

Fibre Optic, Basic Cable Design

Fibre Optic Glossary and Term

How Do Fibre Optics Work?

A Quick Lesson In Optical Transmission

Where copper cabling uses electricity to transmit signals from one end to another, fibre optics use light pulses to accomplish the same purpose. The fibre cable is made of a transparent glass core surrounded by a mirror like covering called cladding. Light passes through the cable, bouncing off the cladding until it reaches the other end of the fibre channel, this is called total internal reflection.

The diameter of the core corresponds directly with the angle of reflection. As this diameter increases, the light requires more reflections and in turn a greater amount of time, to travel a given distance. Single mode fibre optic cable has a smaller diameter core which lends itself to long distance, higher bandwidth runs. Multi-mode fibre has a larger diameter core and is more commonly used in shorter cable runs. Multi-mode cabling is more economical and easier to work with; it is the choice for most local area networks.

At one end of the system is a transmitter. This is the place of origin for information coming on to fibre optic lines. The transmitter accepts coded electronic pulse information coming from copper wire. It then processes and translates that information into equivalently coded light pulses. A light-emitting diode (LED) or an injection-laser diode (ILD) can be used for generating the light pulses. Using a lens, the light pulses are funnelled into the fibre optic medium where they transmit themselves down the line.

Think of a fibre cable in terms of very long cardboard roll from the inside roll of paper towel, that is coated with a mirror.
If you shine a flashlight in one you can see light at the far end, even if bent the roll around a corner.

Light pulses move easily down the fibre optic line because of a principle known as total internal reflection. "This principle of total internal reflection states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in. When this principle is applied to the construction of the fibre optic strand, it is possible to transmit information down fibre lines in the form of light pulses.

Fibre Optic Cabling Compared to Copper

Fibre optic cabling has many advantages that cannot be matched via copper or wireless transmission. First, optical fibre can transport more information to much longer distances in less transmission time. This is because fibre has less attenuation (loss) and more bandwidth (capacity). Aside from distance and speed, optical transmission cannot be affected by electromagnetic radiation (noise), making it handy to use in environments where this is a problem. Fibre is also relatively secure since the optical transmission cannot be tapped as easily as electrical transmission.
In recent years, opto-electronic circuitry has become more standardised and economies of scale have greatly reduced their cost. Due to this, optical transmission is becoming much more common.