Optical fibres: what to know about the tech that powers every call and download
Learn about the science behind thin strands of glass that have made it possible for us to communicate with anyone around the globe
Optical fibres are key to how we send data over long distances. Photo: ShutterstockEvery time you call someone or visit a website, light travels through strands of optical fibre to quickly send data from one place to another. These fibres are an amazing invention that connects billions of people across the globe.
Science behind optical fibres
Optical fibres use light to send data. Information is turned into a code that can be sent with short bursts of light from one end of the fibre to the other.
The light travels through the optical fibre’s core, which is made of glass or plastic. The core is surrounded by a layer of cladding, which keeps the light from escaping the core.
How does the cladding stop the light from leaving? When light hits the boundary between the core and cladding at certain angles, the light reflects back into the core instead of escaping (see graphic).
This is thanks to the materials’ refractive indices, which refers to how much light bends when it passes from one material to another.
The core has a higher refractive index, and the cladding has a lower one. The difference between their refractive indices decides the critical angle where light stops refracting – bending and going through the cladding – and instead is completely reflected, bouncing back into the core. For this to happen, the light needs to hit the boundary between the core and cladding at an angle greater than the materials’ critical angle.
This is called total internal reflection. It allows light to travel along the fibre over long distances without losing much of the signal.
A breakthrough in communication
The idea of using light to send information is more than 100 years old. But the breakthrough in this technology came in the 1960s, thanks to Charles Kao, who grew up in Hong Kong, and his colleague George Hockham.
Before their discovery, data was sent using copper wires and early glass fibres, but these materials would lose some of the signal.
In Kao and Hockham’s research paper published in 1966, they explained that this signal loss was mainly caused by impurities in the glass. They suggested using fibres made of ultra-pure glass. This led to the creation of optical fibres that minimised signal loss. Communication could then be done at high speeds and over long distances.
Kao’s research earned him the Nobel Prize in Physics in 2009, and he became known as the “father of fibre optics”.
Endless possibilities
Optical fibre technology isn’t just used to instantly send data around the world. It also helps doctors see an image of what is happening during surgeries, and in planes and cars, optical fibres help warn drivers and pilots about problems in the vehicles.
As this technology continues to improve, it will continue changing our world.
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