The history of optical fibre communications can be traced back to the mid-19th century when Alexander Graham Bell and his assistant, Thomas Watson, first developed the telephone. Since then, optical fibre communications have become an integral part of our lives. From the initial use of optical fibres in medical imaging and telecommunications, they have since been used in a wide range of applications, including data communications, telecommunications, and computer networks. In this article, we’ll take a look at the history of optical fibre communications and how it has evolved over time.
When was Fibre Optic Cabling first used in Communications?
Optical Fibre Communication was invented in the early 1960’s, at Standard Telecommunication Laboratories, in Harlow in the UK. Watch this fascinating video for a full history on the creation of this revolutionary technology.
How was Optical Fibre Invented?
Optical Fibre reduced significantly the cost of communicating over long distances spanning the entire globe, and so played an integral part in enabling the World Wide Web. At the time, there was an alternative technology to long distance communications – Long Haul Microwave Waveguide (A big hollow pipe). This was in fact being developed by several laboratories around the world. However, its stumbling block was the fact that it would be nearly impossible to place under the sea. The Internet these days relies heavily on submarine cabling to connect our continents together.
As a result of the invention of the laser in 1960, interest was renewed in the potential to replace electricity and radio waves with light as a medium of communication. It was possible to communicate through the air (“free space”), but the weather severely limited the ability to do so, and the majority of network scenarios were not feasible. A small team of people was formed in 1959 at Standard Telecommunication Laboratories in the UK with the objective of exploring possible optical guiding mechanisms.
Initially, all efforts were aimed at finding a solution where the entire optical energy could travel almost entirely through air, due to the high attenuation of light that occurs through glass. Three different approaches were being investigated:
- An optical pipeline with a diameter of 1 inch with an inner surface that is silvered. Even though theory predicted a low loss of 5 dB/mile at shallow reflecting angles, in practice it was a high loss of 200 dB/mile due to the shallow reflective angles involved. In spite of this alone, it was estimated that a bend radius of half a mile could be tolerated, which would have effectively killed the idea.
- A linear array of lenses was placed along a line, each spaced out according to their focal length, each one refocusing the beam of light. This was known as the Confocal Lens system. It became apparent in practice that the system was very sensitive to temperature fluctuations. There was a variety of methods that were proposed for adjusting the lenses automatically to compensate for the fluctuations in temperature. Nevertheless, none of them were successful.
A thin film waveguide is still capable of transmitting light if the dielectric guide is sufficiently thin, however the majority of the energy is still carried by the air on either side of the guide. By using this planar thin-film ribbon guide, it was possible to achieve a low optical loss optical waveguide using a lossy dielectric.
The film was supported at its edges and this caused loss, although the idea of twisting the film to maintain central guidance was proposed as a way to prevent loss. A similar idea was investigated using an incredibly thin glass fibre, however the fibre was too thin to support.
A single-mode glass fibre has long been envisaged as an alternative to traditional multimode fibres, but none of these seemed to have much promise, so Charles Kao and his colleagues decided to explore this possibility, and the rest is history!
Who Invented Fibre Optics?
There is no denying the importance of Sir Charles Kuen Kao‘s legacy.
When the loss of the best available glasses made it seem impossible to use a single-mode dielectric (glass) optical fibre waveguide for long-distance communication, Charles Kao pioneered the use of a single-mode dielectric (glass) optical fibre waveguide. A number of laboratories around the world were developing Long-haul Microwave Waveguide technology, competing with it.
The optical fibre communication technology was recognized with the Nobel Prize in Physics in 2009 for its pioneering work.
There was, of course, a whole team of engineers behind Charles Kao, below is the STL organisation chart for 1967.