October November December Show summaries quick search Search the news archive. Fibre-optic cables usually consist of an inner core of highly refractive glass sheathed inside glass with a lower refractive index.
Light travels along the inner core fibre by total internal reflection.
However, despite their popularity, standard optical fibers have a number of limitations. They are difficult to manufacture, light can leak from the inner core, and it is only possible to change the optical properties of the fibre at one wavelength. In the approach developed at Bath, solid silica rods and hollow silica capillary tubes are stacked in hexagonal arrangement and heated to 2000 Celsius. The silica is then stretched into a fibre that has a pattern of submicron air holes over its cross sectional area. Instead of travelling along a region with a high refractive index, light travels through a region of the fibre containing an extra air hole.