How does optical fiber work?

so again, as I was studying some optics I found something that interested me. This time it was optical fiber which is the cable that may be running under your way to work bringing you some interner connection.

Optical fibers are cables that are carrying signal. They are made of two pieces of glass with different indexes of refraction. When electromagnetic radiation (light) travels through this tunnel that is made by this cable it bounces off the sides if it is in big enough angle.

There is value called critical angle in which light will always bounce on the edge of two mediums. It depends on refractive index.

This kind of communication is very useful one because glass is very cheap compared to some metals and the communication can not be destroyed by some magnetization. Also

The optical fibre has to be protected in some material, the core itself may be in micrometers.

Optical fibres are usually packed in nice groups.






those tubes made up of glass are quite flexible.


By transmitting signal on one side usind some diode you can few kilometers away decode this signal based for example on the number of pauses and number of incoming light waves. Such a communication may reach amazing speeds of tens of gigabytes per second.

There are two main types of optical fibers. First one are multi-mode fibers.Those are the ones for a shorter distance, roughly 600-1,000 meters. There is lot of light running there and it is used to deliver signal in buildings. If you would use it for longer distance the light would stop traveling predictably.

The second type is single-mode fiber. This is much thinner and works on the distance of tens of kilometers. It is used between countries and cities.