On Fibre optic cables

Source: The post on Fibre optic cables has been created on the article “Fibre optic cables: its origins, working and different functions” published in “The Hindu” on 28^th November 2023.

UPSC Syllabus Topic: GS Paper 3 Science and Technology – Developments and their applications and effects in everyday life.

News: The article discusses the working of fibre optics and its applications in everyday life.

What is an optical fibre?

Optical fibres are made of ultra-thin cylindrical strands of glass. These fibres can carry information, such as text, images, videos, telephone calls, and anything that can be encoded as digital information, across large distances almost at the speed of light.

When surrounded by protectives, they are strong, light, and flexible, and ideal to be buried underground or underwater.

A fiber-optic cable is similar to an electrical cable but containing one or more optical fibers that are used to carry light.

They allow a high data-transmission rate. They are also insensitive to external disturbances such as lightning and bad weather.

How do optical fibres work?

Fiber optics work by using the principle of total internal reflection (TIR) to guide light across long distances without a significant loss of optical power.

When light moves from a medium with higher refractive index to one with a lower refractive index, the light may get completely reflected back into the first medium. This phenomenon, known as TIR, happens when the angle of incidence is greater than the critical angle of incidence. Due to TIR, light travels down a fibre optic cable by bouncing off the walls of the cable repeatedly until it reaches the other end.

Note – Critical angle is the angle of incidence where the angle of refraction is 90° and the refracted ray travels along the boundary of the two media.

This is how signals encoded as electromagnetic waves can be fed into one end of an optical fibre, and they will reflect and bounce many times between the glass walls as they traverse large distances bearing the information.

What are the different parts of a fibre optic communication system?

A fibre optic communication system consists of three parts:

1. A transmitter: It encodes information into optical signals (in the form of rapidly blinking light pulses of zeros and ones).
2. An optical fibre: It carries the signal to its destination.
3. A receiver: It reproduces the information from the encoded signal.

How are fibre optics made today?

Nowadays, glass fibres are manufactured using the fibre-drawing technique.

First, a thick glass rod, called preform, of high purity and an engineered refractive index profile is prepared using chemical vapour decomposition.

Second, the preform is heated to about 1,600 degrees Celsius until it melts and is then drawn into a thin, long fibre.

The drawing process reduces the fibre’s diameter while maintaining its length. The drawn fibre is coated with a protective layer to enhance strength and durability.

What are the uses of Fibre optics technology?

It has use cases in telecommunication, medical science (endoscopy), laser technology, and sensing.

Some other uses include in the Automotive industry, CCTV cameras, Television cables, etc.

Terminology Used:

Refractive index: It is a property of a material that measures how much a light ray bends when it passes from one medium to another. It is also defined as the ratio of the velocity of a light ray in an empty space to the velocity of light in a substance.

Question for practice: 

Explain the working of fibre optics. What are its applications in everyday life?