What are fibre optic cables and how do they work? | Explained Premium

Optical fibres, which are thin cylindrical strands of glass, carry info like text, images, voices, videos, etc. Charles Kao predicted their use in telecommunication, for which he won a Nobel Prize in 2009. Light is guided through fibre optic cables using total internal reflection. Transmitter encodes info into optical signals, which are carried by fibre to receiver. Fibres are strong, light, and flexible, and can transmit data up to several terabits/sec.

During the unprecedented COVID-19 pandemic, the one thing that connected us virtually was the internet. Because of high-speed internet connections, we can now video chat with a friend, pay online, and attend classes or meetings from home. Have you wondered how these connections work?

Optical fibres are made of thin cylindrical strands of glass. The diameter of a typical fibre is close to the diameter of a human hair. These fibres can carry information, such as text, images, voices, videos, telephone calls, and anything that can be encoded as digital information, across large distances almost at the speed of light.

Receiving text messages and phone calls is a part of our everyday life, and most of us may have taken it for granted. But optical fibres are an essential part of this development in communication.

Ultra-thin fibres seem very fragile. But when manufactured correctly as a long thread surrounded by protectives, they serve the purpose in a durable way. They are strong, light, and flexible, and ideal to be buried underground, drawn underwater, or bent around a spool.

Almost 60 years ago, physicist Charles Kao suggested that glass fibres could be a superior medium for telecommunication, replacing the copper wires of the time. Many people didn’t believe him at first, but his prediction is a reality today. For his ground-breaking achievements concerning fibre optic communication, Dr. Kao received a part of the 2009 Nobel Prize in physics.

Light is an electromagnetic wave with a spectrum of frequencies. Visible light, X-rays, radio waves, and thermal radiation (heat) all lie on this spectrum. Humans see the world around us via sunlight, but it took us a long time to control and guide light through fibre optic cables – or “light pipes” – to send coded signals.

When a beam of light falls on a glass surface, it passes through partially while the rest is reflected away. When it passes through, its path bends because the refractive index of glass is different from that of air. The refractive index is the property of a medium that determines how fast light can travel in it.