TECHNOLOGY
Today, almost all fibre-based data transmission networks rely on glass (silica), which has the lowest attenuation of all currently used materials. However, researchers working with semiconductor optical fibres may have found a method to convert electrical data into optical signals during transmission for faster delivery. What’s more, this method would require less power. Essentially, this method embeds semiconductors into glass fibre.
In 2006, a group of researchers developed silicon fibres that consisted of a series of crystals. However, these suffered from light being scattered due to imperfections, disrupting transmissions. More recently, however, Xiaoyu Ji, doctoral candidate in materials science and engineering, has managed to improve on the polycrystalline core of fibres. Using a scanning laser, a high-purity amorphous silicon core inside a 1.7-micron inner-diameter glass capillary is melted. This allows the formation of silicon single crystals that are more than 2,000 times as long as they were thick and which have very few imperfections. This means they can transmit light, and therefore data, far more efficiently. Bypassing the input and output conversion stages speeds things up even further.
According to Venkatraman Gopalan, professor of materials science and engineering, Penn State, the crystals could, in theory, be even longer, increasing speed and efficiency even further. However, the equipment used to create the current crystals did not allow this. “Glass is great, but can we do more by using the numerous electronically and optically active materials other than plain glass,” says Gopalan. The technology is not only suitable for communications networks, but could also be used for a wide range of other applications, including imaging, endoscopy or fibre lasers. A variety of materials can be used to make the fibre core.
High-quality, small-core single-crystal germanium fibers are photosensitive at near-infrared and have low optical losses ≈1 dB cm−1 at 2 μm.
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