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- Date published: 23/05/2019
How does fibre optic cable work and what impact is fibre optic cable having on our communications?
Have you ever wondered how you get your Instagram, Twitter, Facebook messages or emails with information from all over the world in just seconds?
This is possible due to a network of fibre optic cables which you mostly cannot even see.
The fibre cable can be buried underground or can be lying on the ocean bed.
Ninety-nine percent of international data is transmitted by fibre optic cable at the bottom of the ocean.
This fibre optic cable network connects the world, without it data traffic comes to an abrupt halt.
To understand how this all can happen you need to understand the technology behind it.
Fibre Optic Technology uses light as its transmission source.
So how does light get transmitted in fibre optic cable?
Optical fibre cable carries information in the form of light. In order to understand how it works, we need to know some of the basic behaviours of light.
One thing we know is that the speed of light changes when it passes through a medium. This is also referred to as the index of refraction.
The index of refraction is mathematically expressed as
Given that C or velocity of light in vacuum is a constant value
We then simply need to now the velocity of light in the medium to calculate the Index of Refraction. See below for examples.
Refraction occurs when light travels from one refractive index to another. Total Internal reflection is used in optical fibre cable to transmit light.
For the optical fibre to guide the optical signal, the refractive index of the core must be slightly higher than that of the cladding.
Both the core and cladding in fibre optic cables use Silica (glass) but have a different refractive index because different dopants are added to the glass at the time of manufacture.
Now we know how the light manages to travel through the core of the fibre.
So how do we achieve such long distances using fibre optic cable?
Most fibre optic cable runs are only 100km due to loss of signal or attenuation.
Absorption or scattering is the main reason for signal loss in a fibre optic cable run.
Light absorption is a major cause of losses in optical fibre during transmission. The light is absorbed in the fibre by the materials of the fibre optic cable. It is not possible to manufacture materials that are totally pure. Therefore, fibre optic manufacturers choose to dope germanium and other materials with pure silica to optimize the fibre optic core performance.
Scattering is another cause for loss in optical fibre. Scattering of light caused by irregularities in the glass structure. When scattering happens, light energy is scattered in all directions.
The solution to the problem is to use amplifiers to boost the signal strength along the fibre cable run.
Now back to the question of how does it work?
Information is sent in Binary Code which is the two-symbol system. A Binary digit can only be “0” or “1” or “on” and “off”. The binary code assigns a pattern of binary digits, also known as bits, to each character or instruction.
This is then sent in electromagnetic waves to the telecommunications tower where it is converted to a light signal which will travel through the complicated global fibre optic network until it reaches the required destination.
Fibre Optic Cable has become the superior cable when connecting the world as it has many benefits:
- Noise Immunity – not affected by EMI or RFI
- Low Loss
– longer distance without repeaters
- High Bandwidth -350 billion bits per second/100km
- Small Size
- Lightweight - 15% less than copper
- Transmission Security
- Wide Temperature Range -40◦ C to +80◦ C
- Greener – silica is in abundance and readily available
- Safe from lightning strikes
Just to name of few!
The demand for internet capacity is only going to increase. In the future, there will be many millions of new devices wanting to connect to the wide world of communications.
Since fibre optic cable uses light to encode information and remains unaffected by such things as the weather, carries data faster and is cheaper than satellites it is unlikely that these systems are going to be replaced by anything else anytime soon.
So the future of fibre optic cable is looking bright!
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