This seminar was delivered by Peter Horak of the University of Southampton's Optoelectronics Research Centre. We heard how optical fibres underpin all modern communications, and are so widespread that their total length would stretch to the Sun and back twenty times. All of this from single fibres the size of a human hair. Their applications now range from telecommunications to sensors to high power lasers.
99% of all communications now happen through optical fibres. The fibres can be tens, hundreds or thousands of kilometres long. They are laid as bundles of fibres, with protection around the outside, including from the occasional shark attack.
Research challenges have included increasing the rate of data transfer down a single fibre. Techniques such as changing the pulse power and phase of the light have allowed more signals to be transmitted down the same fibre. Computational modelling can be used to investigate the attenuation and changes in frequency of light as it passes along the fibre. This allows the effects of changes to be understood and improvements designed which can further increase data transfer rates. The modelling is based on solutions to the non-linear Schrödinger equation, and we have recently seen an application of this in the work of Ioannis Begleris.
The transmission of light through optical fibres is sensitive to parameters such as temperature, strain and humidity. This makes them ideal for use as sensors. They now find application in railway lines, oil wells and wind turbines, for example monitoring vibration and hence a train's position, or the load from the bending of wind turbine blades. They are also ideal for monitoring oil wells because they are very robust, inert and require no electricity.
Microstructured fibres have more complicated structures. A standard optical fibre contains a core and outer cladding both made from glass. A microstructured fibre contains a single glass material surrounded by structures of different shapes containing air. This allows greater control of the properties of the fibre, improving, for example, the transmission of signals down their length. Recent modelling work has simulated the creation of the microstructure. As the fibre is drawn through a furnace the pressure in the core is controlled to alter the fibre's final structure. The model allowed investigation of, for example, the effect of the pressure on the result obtained.
Overall we gained a fascinating insight into the wide range of applications of optical fibres and some of the challenges faced in their development.