Speed of light

Light is reflected in the fibre

Light travels at a speed of 300,000 km / sec. The light will keep this speed indefinitely as long as it is traveling in vacuum. In a fibre, the speed is lower. Even if the core of the fibre is made out of a very clean glass that guides the light through, the speed of light is approximately 2/3 of the speed in vacuum. The light is kept inside the fibre using so-called ”total internal reflection”, which means that the light bounces back at a carefully calculated angle between the core and the cladding. This way, the light can be used to communicate long distances using a transmitter and a receiver.

How can light become a movie on TV?

The transmitter is a laser that transmits light pulses (coded digitally), which travels through the fibre to the receiver. In the receiver, light signals are converted into a digital signal via the modem, which is connected to the TV, computer, phone and any other communication device that we may need.

Fibre vs. copper

The old copper network does not have the capacity to handle the Internet of the future. Copper networks are not capable of development indefinitely and will eventually be phased out. The capacity of a fibre optic cable is virtually limitless and can easily be used simultaneously for telephone, television, Internet and any other communication service of the future.

Advantages of fibre
  • Electromagnetic interference
    The difference from copper - which conducts electrical current – is that fibre light is immune to electromagnetic energy that may adversely affect the signal. Optical fibre is also unaffected by lightning, thus making it a safer method for transferring data.
  • Transmission
    Optical fibre has a higher transmission capacity than copper. A fibre as thin as a human hair is capable of handling hundreds of thousands of phone calls, as opposed to a copper line that can only handle about thirty. Given that a fibre cable can consist of several hundred fibres, fibre network capacity can be - in principle - virtually unlimited.
  • Lower Cost
    Fibre wire is cheaper than copper and can handle much longer distances with very low signal attenuation. This means fewer access switches than a copper network, which requires a switch every 100 meters. The lifetime of fibre is more than 50 years and when it needs to be replaced, requires no new excavation since new cable is simply blown in using compressed air.
  • Non-flammable
    Fibre is dielectric, which means there is no electric current flowing through. Copper however, conducts electricity, which can cause fires if it is old or worn.
  • Distance
    Fibre loses only 3% of its original signal strength per 100 meters. The attenuation of the fibre is not affected when the transfer increases or decreases. The maximum attenuation of 100 meters of copper cabling (Category 6A) 100 MHz is 20.9 dB, which corresponds to a loss of 94%.


See how it works

Video from Fiber Optic Valley

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Technical Description

The image shows fibre cable segments and how the light signal is reflected from the core casing (shell).