Next generation of optical wireless systems will ease our use of gadgets in the workplace and in our homes
In the last decade wireless connectivity by means of wireless technology has become more and more popular, replacing partly wired networks in serving laptop computers, tablet computers, smartphones, and many more wireless gadgets. The booming amount of wireless devices is causing congestion in the commercially available radio spectrum, and their mutual interference is hampering reliable communication. These indoor networks face an exploding demand for more capacity, versatility and flexibility.
According to this study on indoor optical wireless systems, optical fibre-fed routers are optimally suited to meet this demand - thanks to their large bandwidth, and low losses it can offer.
Ariel Gomez Diaz, DPhil student in the Department’s Photonics Group, said: “Light carries information. The communication system that sends light signals from the optical fibre through the air to your computer can provide terabit aggregate capacities to buildings and offices within modern cities. Such indoor optical wireless probably wouldn’t replace Wi-Fi but with a potential for data rates of 3 terabits per second and up, it could certainly find its uses. Wi-Fi, by contrast, tops out at about 7 Gb/s. The link operates over ~3 m range at 224 Gb/s with a wide field of view (FOV) of 36°, respectively. To the best of our knowledge, this is the first demonstration of a wireless link of this type with a FOV that offers practical room-scale coverage”.
Ariel added: “And with light, there’s no worry about sticking to a limited set of radio frequencies. If you’re in the optical spectrum, you have virtually unlimited bandwidth which is unlicensed”.
To accomplish this, the team considered a static base station, which would project the light toward a mobile terminal e.g. a computer and also receive data heading out from the mobile terminal to the Internet.
Professor Dominic O’Brien, the Department’s Associate Director of Research, said: “The key is steering the light beam to where it needs to go. An optical fibre makes for a target that’s only eight or nine micro-metres in diameter. The researchers accomplished this using holographic beam steering at both the transmitter and receiver ends. These use an array of liquid crystals to create a programmable diffraction grating that reflects the light in the desired direction. The device is similar to that used in projectors”.
The next step, Professor O’Brien says, is to develop a tracking and location system so that a user could place a laptop at a random spot on a table and have the system find it and create a link.
Professor O’Brien is a member of the Ultra-Parallel Visible Light Communications project, with colleagues at the Universities of Edinburgh, Strathclyde, St Andrews, and Cambridge. One of their goals is to develop LiFi, which uses the light that’s also illuminating a room as a way to send data signals. LiFi usually refers to schemes based on visible wavelengths of light, whereas this system relies on infrared light at 1550 nm, which is used in telecommunications.
Professor O’Brien added: “All these technologies - Wi-Fi, LiFi, optical wireless - may wind up being part of how people link devices to the Internet. The world of communications is a world where everybody always wants more bandwidth. Industries such as broadcasting and data centres would benefit greatly from the high capacity and speed that the next generation of optical fibre communications brings”.
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