Fiber Optic Cable - Gopi Krishna's Blog

Fiber optics works a third way.
It sends information coded in a beam of light down a glass or plastic pipe.
It was originally developed for endoscopes in the 1950s to help doctors see inside the human body without having to cut it open first.
In the 1960s, engineers found a way of using the same technology to transmit telephone calls at the speed of light.

Optical Technology:

A fiber optic cable is made up of incredibly thin strands of glass or plastic known as optical fibers.
One cable can have a few as two strands or as many as several hundred.
Each strands is less than a tenth as thick as a human hair and can carry something like 25000 telephone calls.
Fiber optic cable carry information between two places using entirely optical technology.

Types:

It is a very thin core about 5-10 microns in diameter.
In a single mode fiber, all signals travels straight down the middle without bouncing off the edges.
Cable TV, internet, and telephone signals are generally carried by single mode fiber, wrapped together into a huge bundle.
It can send information over 100 km.

Each optical fiber in a multi mode cable is about 10 times bigger than one on a single mode fiber cable.
This means light beams can travel through the core by following a variety of different paths in other words in simple multiple different modes.
Multi mode cables can send information only over relatively short distances and are used to link computer networks together.

Working:

Light travels down a fiber-optic cable by bouncing repeatedly off the walls.
Each tiny photon (particle of light) bounces down the pipe like a bobsleigh going down an ice run.
Now you might except a beam of light, travelling in a clear glass pipe, simple to leak out of the edge.
But if the light hits glass at a really shallow angle (less than 45 degrees), it reflect back in again as though the glass were really a mirror, this phenomenon is called total internal reflection.
It's one of the things that keeps light inside the pipe.
The other thing that keeps light in the pipe is the structure of the cable, which is made up of two separate parts.
The main part of the cable in the middle is called the core and that's the bit the light travels through.
Wrapped around the outside of the core is another layer of glass is called cladding.
The cladding's job is to keep the light signals inside the core.