Date posted: 30 October 2018 – Category: Fibre Optics
The man known as the ‘father of fibre optics’, Sir Charles Kuen Kao has died at the age of 84. He was awarded the Nobel prize for physics in 2009 for his work, the citation stating his, “groundbreaking achievements concerning the transmission of light in fibres for optical communication.”
Born in Shanghai, China in 1933, Kao was educated at what is now Greenwich University before going to work for an Essex-based phone company, Standard Telephones and Cables based in Harlow. He went on to gain a PhD in electrical engineering from University College London in 1965 with a thesis on the theme of ‘Waveguides for millimetre and submillimetre electromagnetic waves’.
Dr Kao later went on to become vice-chancellor of the Chinese University of Hong Kong. Other awards garnered in his lifetime include the Alexander Graham Bell Medal in 1985 and the Faraday Medal in 1989.
In the mid-1960s Kao pioneered the idea of sending data at the speed of light through glass fibres. Today this technology is at the heart of what makes our high-speed internet and global communication network possible.
Dr Kao was diagnosed with Alzheimer’s Disease in 2004 and with the assistance of his wife Gwen, he founded the Charles K Kao Foundation to promote research into the condition.
Many academics have paid tributes to Kao’s achievements. UCL president and provost, Professor Michael Arthur, said, “Sir Charles Kao was a giant of science, a great man and his place in history as the father of modern communications is assured; few people are able to make such an impression on the world as he has done.”
Sir Charles Kao died in Hong Kong, on 23 September 2018.
Fibre optic technology is key to the modern communications environment, yet it relies on the basic principles that Kao discovered in the 1960s. It uses optically pure fibre, usually made of glass and the thickness of a human hair. This transmits data in the form of pulses of light which can travel down the fibre at very high speed.
Optic fibre cables are usually made up of a bundle of individual fibres, allowing them to provide greater bandwidth. Each individual fibre is made up of an inner core, down which the light travels. Around this is a cladding which is reflective so that it bounces light back into the core – allowing the fibre to be bent around corners. Finally, there’s an outer coating to protect the fibre from damage.
The actual transmission of data works in much the same way as signalling in Morse code using a lamp. The difference is that the rate of on/off flashing is much, much faster because there’s no human involved, and because the signal is passing down the glass fibre you don’t need line of sight between the transmitter and the receiver.
Optic fibres as devised by Kao were originally made of glass, and many still are, although there are now three different types in common use. Single mode fibres use a core that measures around about nine microns in diameter. These are designed to transmit light generated by a laser. Combining a narrow fibre and a single light wave in this way allows transmission at high speed over longer distances.
There are also multimode fibres; these are larger with a diameter of about 62 microns and are made to transmit infrared light produced by LEDs. Multi-mode fibre allows the light to be dispersed into several paths which means signal loss or distortion can occur at shorter distances than with single mode fibres, typically around 914 metres. For fast networks, therefore, it’s more common to use single-mode fibre to ensure reliable operation.
Finally, there are plastic fibres which have a much larger diameter of around one millimetre. These are made to transmit visible wavelength light, again produced by LEDs. Plastic fibre is a lot cheaper, and it’s rather more robust than glass, however, it can only be used reliably over much shorter distances.
So, what are the advantages of using fibre optic cable and why has it so revolutionised the world of telephone and computer communication?
Historically, networks have used copper cable as a transmission medium. This is because it offered a low level of loss compared to other metals. Kao’s discovery as to how fibre could be used gave us a new transmission medium with far lower loss than copper.
To put this into perspective, copper offers speeds of up to 1Gbps over distances of up to 100 metres. Any longer than this and you will need some technology to boost the signal. By contrast, fibre can transmit at up to 10Gbps, or even more, at distances of up to 2Kms before signal loss starts to become an issue.
In addition to its speed, there are other advantages to fibre cabling. First of all, it’s more secure because, unlike copper cable, it’s much more difficult to tap into the signal on a fibre circuit. This makes it an enduringly popular choice for internal networks for businesses that need to keep their information safe from potential eavesdroppers.
Fibre is also useful in industrial situations where there may be a fire hazard – such as oil and gas production – as it represents no spark hazard, unlike conventional network cabling. It also is not subject to electrical interference, again making it useful in situations in which heavy machinery might produce high levels of interference and signal noise. In these circumstances, copper cable would need to be properly shielded, making it more expensive to install. This lack of susceptibility to electrical interference also means that there’s no chance of crosstalk between cables when they are laid together in ducting, for example.
Fibre is durable too, it can withstand harsh environments and extremes of temperature much better than copper cables. Again this reduces the need for the cables to be shielded during installation.
The major advantage of fibre, of course, is its speed and this also helps to make it future proof. Although you may not need the ultra-fast speeds fibre can offer now, by installing it today you can ensure your business network has the capacity it needs to expand in future. Although fibre is still more expensive than copper it is getting cheaper and the difference looked at as a long-term investment is likely to be marginal.
As with any technology, there are some downsides to using fibre. Boosters may be needed over longer distances to prevent a drop in signal quality. In addition, fibre can’t turn sharp corners to the same extent as copper cable. This means it needs care in installation to ensure that the fibre doesn’t get damaged during the process, and means that cable routes through buildings need to be carefully planned to avoid problems.
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